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Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 7 — Apr. 8, 2013
  • pp: 9091–9102
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2.1-watts intracavity-frequency-doubled all-solid-state light source at 671 nm for laser cooling of lithium

U. Eismann, A. Bergschneider, F. Sievers, N. Kretzschmar, C. Salomon, and F. Chevy  »View Author Affiliations


Optics Express, Vol. 21, Issue 7, pp. 9091-9102 (2013)
http://dx.doi.org/10.1364/OE.21.009091


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Abstract

We present an all-solid-state laser source emitting up to 2.1 W of single-frequency light at 671 nm developed for laser cooling of lithium atoms. It is based on a diode-pumped, neodymium-doped orthovanadate (Nd:YVO4) ring laser operating at 1342 nm. Optimization of the thermal management in the gain medium results in a maximum multi-frequency output power of 2.5 W at the fundamental wavelength. We develop a simple theory for the efficient implementation of intracavity second harmonic generation, and its application to our system allows us to obtain nonlinear conversion efficiencies of up to 88%. Single-mode operation and tuning is established by adding an etalon to the resonator. The second-harmonic wavelength can be tuned over 0.5 nm, and mode-hop-free scanning over more than 6 GHz is demonstrated, corresponding to around ten times the laser cavity free spectral range. The output frequency can be locked with respect to the lithium D-line transitions for atomic physics applications. Furthermore, we observe parametric Kerr-lens mode-locking when detuning the phase-matching temperature sufficiently far from the optimum value.

© 2013 OSA

1. Introduction

Lithium atoms are one of the most versatile species used for research on quantum gases. Nature offers significantly abundant bosonic and fermionic isotopes to the experimentalist, allowing the study of both types of quantum statistics [1

1. S. Giorgini, L. P. Pitaevskii, and S. Stringari, “Theory of ultracold atomic Fermi gases,” Rev. Mod. Phys. 80, 1215–1274 (2008) [CrossRef] .

] in the atomic physics lab. The simple yet powerful technique of magnetic Feshbach tuning of the atomic interactions [2

2. C. Chin, R. Grimm, P. Julienne, and E. Tiesinga, “Feshbach resonances in ultracold gases,” Rev. Mod. Phys. 82, 1225–1286 (2010) [CrossRef] .

] is the quintessential ingredient for a large number of experiments, and it explains the outstanding role the lithium atom has played in the development of the field.

For realizing a degenerate quantum gas, one needs to implement different laser cooling schemes which typically require near-resonant single-frequency light input in the watt range. The benefits of all-solid-state designs like large output power, high reliability, low maintenance effort and high intrinsic stability are helpful for realizing light sources that will be welcome tools for every ultracold atom experiment.

We will present in this article an all-solid-state laser emitting multi-watt single-frequency radiation near 671 nm. The diode-pumped design is based on neodymium-doped orthovanadate (Nd:YVO4) as the gain medium, lasing at the fundamental wavelength of 1342 nm. Second harmonic generation (SHG) is then established using periodically-poled potassium titanyl phosphate (ppKTP) as the nonlinear medium. Both materials show optimum performances for generating high powers at our target wavelength. The development of a number of related laser sources has been published recently [3

3. F. Hou, L. Yu, X. Jia, Y. Zheng, C. Xie, and K. Peng, “Experimental generation of optical non-classical states of light with 1.34 μm wavelength,” Eur. Phys. J. D 62, 433–437 (2011) [CrossRef] .

5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

], and the system realized in our group [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

] has proven highly reliable in every-day operation over the period of one year. However, the forementioned sources are currently limited to output powers in the few-hundred-milliwatts regime. We have identified two major limitations for pushing the single-frequency Nd:YVO4-ppKTP concept into the multi-watt range, which are the loss introduced by thermal lensing in the gain medium, and the nonlinear conversion efficiency. Therefore, one key ingredient of our novel high-power design is an improved heat management in the Nd:YVO4. Intra-cavity second harmonic generation (ICSHG) is a well-established concept and very efficient [4

4. F. Camargo, T. Zanon-Willette, T. Badr, N. Wetter, and J. Zondy, “Tunable single-frequency Nd:YVO4 BiB3O6 ring laser at 671 nm,” IEEE J. Quantum Elect. 46, 804–809 (2010) [CrossRef] .

] at several wavelengths. For instance, thanks to large progress in crystal quality at the Nd:YAG wavelength and in doubling crystal designs, commercial devices now deliver tens of watts of single-frequency output at 532 nm. This has stimulated us to explore the novel approach using the material combination mentioned above in the 671 nm wavelength range for atomic physics applications with lithium atoms. Furthermore, we carefully specify the important parameters of the laser output and find that it largely satisfies the exigencies of laser cooling. Our source has successfully been used in the implementation of a gray-molasses cooling scheme for lithium atoms, see Ref. [6

6. D. Fernandes, F. Sievers, N. Kretzschmar, S. Wu, C. Salomon, and F. Chevy, “Sub-doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses,” Europhys. Lett. 100, 63001 (2012) [CrossRef] .

].

Apart from laser cooling of atoms, more applications in the fields of atomic physics and nonlinear optics are currently limited by the available single-frequency 671-nm power. In atom interferometers, a larger and thus more homogeneous gaussian beam can increase the signal-to-noise ratio. The large spatial splitting of the atomic wavepackets employing the lightweight lithium species is favorable [7

7. A. Miffre, M. Jacquey, M. Büchner, G. Trénec, and J. Vigué, “Atom interferometry measurement of the electric polarizability of lithium,” Eur. Phys. J. D 38, 353–365 (2006) [CrossRef] .

], and can even be increased using multi-photon Bragg scattering [8

8. H. Müller, S.-w. Chiow, Q. Long, S. Herrmann, and S. Chu, “Atom interferometry with up to 24-photon-momentum-transfer beam splitters,” Phys. Rev. Lett. 100, 180405 (2008) [CrossRef] [PubMed] .

] when high-intensity laser beams are employed. Furthermore, the lithium D-line isotope splitting is large enough to allow selective addressing of the isotopes in hot vapors, making a narrow-bandwidth source attractive for lithium isotope separation [9

9. I. E. Olivares, A. E. Duarte, E. A. Saravia, and F. J. Duarte, “Lithium isotope separation with tunable diode lasers,” Appl. Opt. 41, 2973–2977 (2002) [CrossRef] [PubMed] .

]. In addition, the creation and long-distance transmission of entangled photons in the low-dispersion, low-absorption wavelength region of standard silica fibers near 1.3 μm has recently been proposed. The scheme uses the output of a sub-threshold optical parametric oscillator in the degenerate regime pumped by a single-frequency 671-nm laser [3

3. F. Hou, L. Yu, X. Jia, Y. Zheng, C. Xie, and K. Peng, “Experimental generation of optical non-classical states of light with 1.34 μm wavelength,” Eur. Phys. J. D 62, 433–437 (2011) [CrossRef] .

]. Finally, our laser could serve as a low-intensity-noise pump for Cr:LiSAF lasers [10

10. S. A. Payne, L. K. Smith, R. J. Beach, B. H. T. Chai, J. H. Tassano, L. D. DeLoach, W. L. Kway, R. W. Solarz, and W. F. Krupke, “Properties of Cr:LiSrAIF6 crystals for laser operation,” Appl. Opt. 33, 5526 (1994) [CrossRef] [PubMed] .

].

The article is organized as follows: In Section 2 we present the optimization of the fundamental laser design. In Section 3, we implement intracavity second harmonic generation. In Section 4, we report on the course and continuous fine tuning behavior and nonlinear-Kerr-lens mode locking, and we conclude in Section 5.

2. The fundamental laser

A first step towards a stable high-power frequency doubled laser source is the availability of an efficient laser system at the fundamental wavelength. To minimize detrimental thermal effects in the gain medium, the following pathway has been chosen: A pump wavelength of 888nm in contrast to the former 808nm [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

] leads to a lower quantum defect per absorption-emission cycle [11

11. L. McDonagh, R. Wallenstein, R. Knappe, and A. Nebel, “High-efficiency 60 W TEM00 Nd:YVO4 oscillator pumped at 888 nm,” Opt. Lett. 31, 3297–3299 (2006) [CrossRef] [PubMed] .

], and thus to lower heating for a given pump rate. In addition, a larger value for the laser crystal length has been chosen in order to spread the heat input over a bigger volume. Therefore, heat transport from the central region to the crystal mount is facilitated. The Nd:YVO4 peak temperature is lower, and thermal issues are less of a concern.

A schematic overview of the laser setup is given in Fig. 1. The output of an 888-nm fiber-coupled diode laser bar (NA = 0.22, 400μm fiber core diameter) is imaged by two lenses (f1 = 75mm, f2 = 200mm) into the 1.0 % at.-doped Nd:YVO4 crystal. The crystal (a-cut, 4 × 4 × 25mm3, anti-reflection coated on both sides for 1342nm and 888nm) is wrapped in indium foil and mounted in a water-cooled copper block. The mirrors M1–4 constitute a bow-tie cavity. M1, M3 and M4 are highly reflective at 1342nm, and M1 is transmitting at 888 nm. M3 and M4 are concave mirrors with a radius of curvature of 100mm. M2 is the output coupler for which mirrors with different values of transmission are available. The cavity dimensions are M1M2 ≈ 300mm, M2M3 ≈ M1M4 ≈ 210mm and M3M4 ≈ 97mm. For forcing unidirectional operation we use a Faraday rotator consisting of a terbium-gallium-garnet rod-shaped crystal (TGG) of 6mm length embedded in a strong permanent magnet [12

12. G. Trénec, W. Volondat, O. Cugat, and J. Vigué, “Permanent magnets for Faraday rotators inspired by the design of the magic sphere,” Appl. Opt. 50, 4788–4797 (2011) [CrossRef] [PubMed] .

] in combination with a true-zero-order half-wave plate. An uncoated infrared fused silica etalon of 500μm thickness serves as a wavelength selective element.

Fig. 1 The laser setup. The pump source, a fiber-coupled diode laser bar (FP), is imaged into the gain medium by a pair of lenses f1 and f2. The Nd:YVO4 gain medium is placed in a four-mirror bow-tie ring resonator consisting of mirrors M1–4, which are highly reflecting at 1342 nm. Unidirectional operation is forced employing a terbium gallium garnet (TGG)-based Faraday rotator in combination with a half-wave plate (λ/2). The use of an etalon (E) allows for stable single-longitudinal-mode operation. The nonlinear crystal (pp-KTP) is inserted at the tight focus between the curved mirrors M3 and M4. The second harmonic output beam (red) is transmitted through M3. For the measurements presented in Section 2, the ppKTP was removed and the distance M3–M4 adjusted accordingly, and the high-reflectivity mirror M2 was replaced by a partly transmitting output coupling mirror. The fundamental laser beam (green) is then coupled out through M2.

For maximum power output, it is crucial to optimize the overlap of the pump beam and the cavity mode [13

13. P. Laporta and M. Brussard, “Design criteria for mode size optimization in diode-pumped solid-state lasers,” IEEE J. Quantum Elect. 27, 2319–2326 (1991) [CrossRef] .

, 14

14. Y. F. Chen, T. M. Huang, C. F. Kao, C. L. Wang, and S. C. Wang, “Optimization in scaling fiber-coupled laser-diode end-pumped lasers to higher power: influence of thermal effect,” IEEE J. Quantum Elect. 33, 1424–1429 (1997) [CrossRef] .

]. For simplicity, we perform this operation on the empty laser cavity, consisting of M1–4 and the Nd:YVO4only. We apply the maximum value of the absorbed pump power Pabs,max = 32.5W, and a 𝒯 = 5%-transmission output coupler (M2). By changing the magnification of the pump imaging setup consisting of f1 and f2, the top-hat shaped pump spot diameter was altered between 1080μm and 1400μm, see Fig. 2. The size of the cavity mode in the laser crystal can be changed using the curved mirror distance M3M4, and was optimized for each data point. The maximum output power is obtained at a pump diameter of around 1300μm, where it is kept for the remainder of this article.

Fig. 2 (a) Optimization of the output power by changing the pump spot diameter, performed on the laser cavity presented in Fig. 1 with all the intracavity elements removed, except for the Nd:YVO4. For a 𝒯 = 5% output coupler (M2), the mode overlap was optimized for each pump spot diameter by slight adjustments of the curved-mirror distance M3–M4. Lines are guides to the eye only. (b) Rigrod analysis. The infrared output power Pω is measured as a function of the output coupler transmission 𝒯 and fitted with the Rigrod model (1) for bidirectional (red diamonds, dashed line) and unidirectional (blue circles, solid line) operation at Pabs,max = 32.5W and optimized mode overlap. In both cases the optimum transmission is found at 𝒯 ≈ 5%. The parasitic roundtrip loss determined from the fits yield 10(4)% for the bidirectional and = 16(6)% for the unidirectional case.

For both the bidirectional (empty cavity only containing Nd:YVO4) and the unidirectional (additional TGG and half-wave plate) operation we measured the maximum output power as a function of the output coupler transmission, see Fig. 2. In both cases a 𝒯 = 5% mirror delivers the maximum fundamental output power Pω. By equating the single-pass gain with the total round-trip loss tot = + out = + 𝒯 for both the bi- and unidirectional cases, where is the sum of the parasitic round-trip losses, we find
Pω=Psat𝒯[G0𝒯+1]
(1)
similarly to [15

15. W. Rigrod, “Gain saturation and output power of optical masers,” J. Appl. Phys. 34, 2602–2609 (1963) [CrossRef] .

], where Psat is the saturation power, G0 the small-signal gain and the sum of the parasitic round-trip losses. Although this analysis essentially relies on plane waves, it can be mapped to the more realistic case of top-hat pump beams and gaussian laser cavity eigenmodes, as present in diode-pumped solid-state lasers, see [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

] and references therein. A least-squares fit to (1) yields = 10(4)% for the parasitic loss in the bidirectional case. In [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

] we found the loss in an empty four-mirror bow-tie cavity of mirrors from the same batch to be smaller than 1%. We attribute the remaining 9(4)% mainly to aberrations caused by the thermal lens in the Nd:YVO4.

In the unidirectional case, the fitting procedure yields = 16(6)%. Compared to the bidirectional case, the difference of Faraday = 6(7)% can be attributed to the insertion of the TGG crystal and the waveplate. Indeed, thermal depolarization and the accompanying loss is a well-known effect in TGG. It imposes stringent limits on power scaling of unidirectional ring lasers and Faraday isolators [16

16. E. Khazanov, N. Andreev, A. Mal’shakov, O. Palashov, A. Poteomkin, A. Sergeev, A. Shaykin, V. Zelenogorsky, I. Ivanov, R. Amin, G. Mueller, D.B. Tanner, and D.H. Reitze, “Compensation of thermally induced modal distortions in Faraday isolators,” IEEE J. Quantum Elect. 40, 1500–1510 (2004) [CrossRef] .

]. We observe a dependence of the optimum half-wave plate angle on the circulating intracavity power, which is strong evidence of this effect. From the fit, we furthermore obtain the values Psat = 170(50) W and G0 = 0.27(5) for unidirectional operation, which are important for the optimization of intracavity doubling, see Section 3.

For the now-optimized unidirectional infrared setup, we measure the output power as a function of the absorbed pump power Pabs, see Fig. 3. As the optimization is performed at the maximum absorbed pump power Pabs,max ≈ 32.5 W, the laser emission only starts at Pabs ≈ 28 W. After reaching threshold, the output power is unstable and displays a hysteresis feature between Pabs = 29 W and 30 W. After crossing the hysteresis region, the laser emission is stable and only weakly depends on Pabs. This behavior is typical for high-power solid-state laser designs and has been reported in [17

17. F. Lenhardt, M. Nittmann, T. Bauer, J. Bartschke, and J. L’huillier, “High-power 888-nm-pumped Nd:YVO4 1342-nm oscillator operating in the TEM00 mode,” Appl. Phys. B 96, 803–807 (2009) [CrossRef] .

]. As discussed before, thermal depolarization in the TGG is significant and can lead to a change of the lasing direction and occasional bistable behavior when increasing the pump power. Thus, the angle of the half-wave plate had to be adjusted for every data point presented here. We keep the pump power constant at Pabs,max ≈ 32.5 W in the remainder of the article.

Fig. 3 Infrared unidirectional output power Pω as a function of the absorbed pump power Pabs. The setup is optimized for the maximal absorbed pump power Pabs,max = 32.5 W. The oscillation threshold is found at Pabs ≈ 28W. The data shows hysteresis between Pabs = 29W and 30 W, as indicated by the arrows for increasing or decreasing pump power. This behavior is typical for high-power designs. After a sudden rise the output power increases only slowly until it eventually reaches the maximum of 2.5W at Pabs,max. Lines are guides to the eye only.

3. Efficient intracavity second-harmonic generation

Efficient frequency doubling of infrared lasers can be established using periodically-poled nonlinear crystals in an external cavity. Using this method at a fundamental wavelength of 1342 nm, a doubling efficiency of P2ω/Pω = 86% has been obtained in our first-generation setup [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

], and serves as a benchmark. However, a more direct approach followed here is ICSHG, which requires only one cavity and thus represents an important simplification.

For the analysis of the output power of ICSHG lasers, the ouput coupling loss out = 𝒯 discussed in Section 2 needs to be replaced by ηP, where η is the single-pass doubling efficiency, and P the circulating intracavity power. Similar to the one found in [18

18. R. Polloni and O. Svelto, “Optimum coupling for intracavity second harmonic generation,” Quantum Electronics, IEEE J. Quantum Elect. 4, 528–530 (1968) [CrossRef] .

, 19

19. R. Smith, “Theory of intracavity optical second-harmonic generation,” IEEE J. Quantum Elect. 6, 215–223 (1970) [CrossRef] .

], the solution for the SH output power in the unidirectional case reads
P2ω=PsatG0ξ[(ξζ)2+ξ(ξ+ζ)]2,
(2)
where ξ = ηPsat(4G0)−1 and ζ = (4G0)−1 are the dimensionless output coupling and loss parameters. As pointed out in [18

18. R. Polloni and O. Svelto, “Optimum coupling for intracavity second harmonic generation,” Quantum Electronics, IEEE J. Quantum Elect. 4, 528–530 (1968) [CrossRef] .

, 19

19. R. Smith, “Theory of intracavity optical second-harmonic generation,” IEEE J. Quantum Elect. 6, 215–223 (1970) [CrossRef] .

], it is interesting to note that the value for the optimum output coupling out,opt=G0 is the same for both linear and non-linear output coupling mechanisms, and delivers the same amount of output power. However, the round-trip parasitic loss will contain an additional contribution from the insertion of the nonlinear medium. Hence, P2ω/Pω < 1 for any realistic system, but efficiencies very close to one can be obtained in practice [20

20. J. Zondy, F. Camargo, T. Zanon, V. Petrov, and N. Wetter, “Observation of strong cascaded Kerr-lens dynamics in an optimally-coupled cw intracavity frequency-doubled Nd:YLF ring laser,” Opt. Express 18, 4796–4815 (2010) [CrossRef] [PubMed] .

]. Using the fit values from Section 2, we maximize (2) by choosing an optimum single-pass doubling efficiency ηopt = 0.10(5)%.W−1.

To evaluate η, we refer to the Boyd-Kleinman theory for focused gaussian beams [21

21. G. D. Boyd and D. A. Kleinman, “Parametric interaction of focused gaussian light beams,” J. Appl. Phys. 39, 3597–3639 (1968) [CrossRef] .

],
η(T)=2ω3dij2Lπε0c4nω,i(T)n2ω,j(T)×h[α,β(T)],
(3)
where ε0 is the vacuum permittivity, c the speed of light in vacuum, dij is the i, j-th element of the material’s nonlinear tensor, nω,i(T) the material’s refractive index along the i axis at angular frequency ω and temperature T, and L the nonlinear material’s length. dij needs to be replaced by deff = 2diiπ−1 for periodically poled (pp) materials. The function
h[α,α0,β(T)]=14α|αα0αα0eiβ(T)τ1+iτdτ|2,
(4)
is the dimensionless Boyd-Kleinman function [21

21. G. D. Boyd and D. A. Kleinman, “Parametric interaction of focused gaussian light beams,” J. Appl. Phys. 39, 3597–3639 (1968) [CrossRef] .

]. α = L(2zR)−1 and α0 = z0 (2zR)−1 are the focusing and offset parameters, respectively. zR is the Rayleigh length, and z0 is the offset of the beam focus with respect to the nonlinear medium’s center. The phase-matching parameter reads β(T) = 4πzRλ−1 × {nω,i(T) − n2ω,j(T) − λ [2Λ(T)]−1}, where λ is the vacuum wavelength. The Λ(T) term only occurs for periodically poled materials, where Λ(T) is the poling period, and the temperature dependence results from thermal expansion.

In Fig. 4 we present the measurement of the second-harmonic output power as a function of the phase-matching temperature of the ppKTP crystal. We find a maximum of 2.1 W of output power at Tpm = 36°C, and a second maximum of 1.9 W at Tpm = 31°C. As expected from Eq. (2), at the perfect phase matching temperature η > ηopt, and the output power only amounts to 1.6 W. The FWHM of the temperature-tuning curve amounts to 22 K. As compared to the maximum infrared power presented in the former section, we obtain a maximum doubling efficiency of 88%. The excellent mode quality of the second-harmonic light is confirmed by a single-mode fiber coupling efficiency larger than 80%.

Fig. 4 Output power as a function of the phase-matching temperature (points, blue lines are a guide to the eye only). The data shows a double-peak structure of 1.9 W / 2.1 W of output power slightly off of the optimum phase-matching temperature of 33.2°C (central vertical line). A simple theoretical model presented in the text (dash-dotted purple line) describes the data well in the central high-conversion region, using the known temperature dependence of the single-pass doubling efficiency, which is proportional to the dimensionless Boyd-Kleinman function h(T) [dashed gold line, Eq. (4)]. The dashed vertical line indicates the perfect phase-matching temperature of Tpm = 33.2°C, where β(Tpm) ≃ 0, and the nonlinear output coupling is too high to reach maximum output power. The vertical lines with arrows indicate the temperature regions where self-mode locking occurs, cf. Section 4.

To gain deeper insight in our data, we employ the ICSHG theory (Eqs. (2)(4)). We include the additional parasitic intracavity loss due to the presence of the etalon and the nonlinear crystal, which amounts to add = 0.6(1)%. Thus, the theory predicts a maximum SH output power of 2.1 W, as is found experimentally. The value of add is compatible to the sum of the ppKTP insertion loss measured independently [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

] and the calculated walk-off loss for the etalon [25

25. U. Eismann, “A novel all-solid-state laser source for lithium atoms and three-body recombination in the unitary Bose gas,” Ph.D. thesis, Université Pierre et Marie Curie – Paris VI, http://tel.archives-ouvertes.fr/tel-00702865/(2012).

]. From an ABCD-matrix formalism we obtain the cavity eigenmode, yielding zR = 11.5 mm and z0 = 3mm. At perfect phase matching, we obtain h = 0.40, yielding a SH output power of 1.6 W, which is in excellent agreement with our findings. This gives us further confidence in our previously measured value of d33[5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

]. The temperature-dependent KTP refractive indices and the thermal expansion coefficient of the poling period were presented in [22

22. K. Fradkin, A. Arie, A. Skliar, and G. Rosenman, “Tunable midinfrared source by difference frequency generation in bulk periodically poled KTiOPO4,” Appl. Phys. Lett. 74, 914–916 (1999) [CrossRef] .

, 23

23. S. Emanueli and A. Arie, “Temperature-dependent dispersion equations for KTiOPO4 and KTiOAsO4,” Appl. Opt. 42, 6661–6665 (2003) [CrossRef] [PubMed] .

]. We adjust β by an additive constant in order to account for the measured phase matching condition β(T = 33.2°C) = 0, as justified before. The theory (solid purple line in Fig. 4) describes the data well in the central high conversion region, and yields the characteristic double-peak structure.

Outside of the central region, the circulating intracavity power rises significantly and the power-dependent thermal depolarization loss would need to be accounted for in our simple model. As compared to the theory, the data displays less evidence of dips. This can be explained by a thermal smearing effect due to residual absorption in the ppKTP at large powers, yielding a spatial dependence of the phase-matching parameter β(T). Outside of the region indicated by the solid vertical lines, the laser is in mode-locked (pulsed) operation, and we do not expect our model to be applicable.

4. Tuning behavior and nonlinear-Kerr-lens mode locking

For course tuning and single-longitudinal-mode (SLM) operation, the laser was equipped with an uncoated etalon of 0.5 mm length, yielding a free spectral range of 210 GHz. We note that this single, weakly-selective etalon is sufficient for this purpose due to the self suppression of axial mode hopping in intracavity-frequency-doubled lasers [26

26. K. I. Martin, W. A. Clarkson, and D. C. Hanna, “Self-suppression of axial mode hopping by intracavity second-harmonic generation,” Opt. Lett. 22, 375–377 (1997) [CrossRef] [PubMed] .

, 27

27. S. Helmfrid and K. Tatsuno, “Stable single-mode operation of intracavity-doubled diode-pumped Nd:YVO4 lasers: theoretical study,” J. Opt. Soc. Am. B 11, 436–445 (1994) [CrossRef] .

].

The tuning range of the frequency-doubled laser is characterized and compared to the infrared laser in Fig. 5. Apart from having the same shape and features, it is striking to note that the output power of the frequency-doubled laser amounts to almost the same value as the non-doubled laser over the entire emission spectrum. As discussed in Section 3, the nonlinear output coupling is close to the optimum level over the entire emission wavelength range. The gain line center, where the output power is maximal, is found at around 671.1 nm, resulting in 2.2 W of fundamental and 2.1 W of second-harmonic output. At the lithium-D line wavelength the output power amounts to ≈1.8 W. Being close to the gain line center, this result compares favorably to the value obtained in [4

4. F. Camargo, T. Zanon-Willette, T. Badr, N. Wetter, and J. Zondy, “Tunable single-frequency Nd:YVO4 BiB3O6 ring laser at 671 nm,” IEEE J. Quantum Elect. 46, 804–809 (2010) [CrossRef] .

], where the authors used an etalon for tuning which potentially produces significantly higher tilt loss [25

25. U. Eismann, “A novel all-solid-state laser source for lithium atoms and three-body recombination in the unitary Bose gas,” Ph.D. thesis, Université Pierre et Marie Curie – Paris VI, http://tel.archives-ouvertes.fr/tel-00702865/(2012).

, 28

28. W. Leeb, “Losses introduced by tilting intracavity etalons,” Appl. Phys. A 6, 267–272 (1975).

]. Comparing the emitted power of the doubled and non-doubled lasers across the emission spectra, we typically obtain more than 80% of the power at 671 nm, demonstrating a very efficient frequency doubling process. For the absolute maximum values, we obtain P2ω/Pω = 88%. It is even possible to obtain emission further away from resonance, where the non-ICSHG lasers cease to oscillate. Our first-generation source presented in [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

] displays an output spectrum that is significantly more plateau-like (gold triangles in Fig. 5), which we attribute to the presence of a second, more selective etalon in the cavity. At the expense of a higher insertion loss baseline, ripples in the emission spectrum have significantly less influence on the tuning behavior of this setup. The identical gaps in all of the emission spectra presented here (A,B,C in Fig. 5) can be explained by absorption from water vapor, as we compare the laser spectra to a water vapor absorption spectrum obtained from the HITRAN database [29

29. L. Rothman, I. Gordon, A. Barbe, D. Benner, P. Bernath, M. Birk, V. Boudon, L. Brown, A. Campargue, J.-P. Champion, K. Chance, L. Coudert, V. Dana, V. Devi, S. Fally, J.-M. Flaud, R. Gamache, A. Goldman, D. Jacquemart, I. Kleiner, N. Lacome, W. Lafferty, J.-Y. Mandin, S. Massie, S. Mikhailenko, C. Miller, N. Moazzen-Ahmadi, O. Naumenko, A. Nikitin, J. Orphal, V. Perevalov, A. Perrin, A. Predoi-Cross, C. Rinsland, M. Rotger, M. imekov, M. Smith, K. Sung, S. Tashkun, J. Tennyson, R. Toth, A. Vandaele, and J. V. Auwera, “The HITRAN 2008 molecular spectroscopic database,” J. Quant. Spectrosc. Ra. 110, 533 – 572 (2009) [CrossRef] .

]. The water absorption peaks coincide with the features A,B and C.

Fig. 5 (Lines are guides for the eye only) Single-frequency output spectra of the infrared laser presented in Section 2 (blue circles), the intracavity-frequency-doubled laser (purple squares) and the infrared source presented in [5] (gold triangles). For easy comparison, all wavelengths are given in vacuum values. The vertical lines denote the positions of the lithium-D line resonances. The green line shows a water vapor absorption spectrum for typical parameters (23 °C, 60% rel. humidity). The wavelength regions marked A,B,C where stable, powerful operation of the lasers can not be established coincide with absorption peaks of water molecules. The level of output power of the infrared laser and the frequency-doubled laser are closely spaced, proving that the nonlinear crystal introduces weak additional passive loss in the laser cavity, whereas the degree of nonlinear output coupling is at its optimum value.

Intracavity-frequency-doubled lasers tend to mode-locked operation when the doubling crystal is mismatched from the optimum phase matching condition [30

30. R. DeSalvo, D. J. Hagan, M. Sheik-Bahae, G. Stegeman, E. W. V. Stryland, and H. Vanherzeele, “Self-focusing and self-defocusing by cascaded second-order effects in KTP,” Opt. Lett. 17, 28–30 (1992) [CrossRef] [PubMed] .

, 31

31. S. Holmgren, V. Pasiskevicius, and F. Laurell, “Generation of 2.8-ps pulses by mode-locking a Nd:GdVO4 laser with defocusing cascaded kerr lensing in periodically poled KTP,” Opt. Express 13, 5270–5278 (2005) [CrossRef] [PubMed] .

]. This effect, resulting from an intensity-dependent phase shift of the fundamental beam passing the non-matched crystal, is commonly termed nonlinear-Kerr-lens- or χ(2) : χ(2) mode locking. Although it has been observed in the 1064-nm-Nd:YVO4-ppKTP system before [32

32. C. Schäfer, C. Fries, C. Theobald, and J. A. L’huillier, “Parametric Kerr lens mode-locked, 888 nm pumped Nd:YVO4 laser,” Opt. Lett. 36, 2674–2676 (2011) [CrossRef] [PubMed] .

], we report, to the best of our knowledge, the first observation at 1342 nm. We observe the effect when detuning from the optimum phase-matching temperature to below Tlow =29°C and above Thigh =45°C. A scanning Fabry-Perot spectrum analyzer shows no discernible single- or few-mode background once the threshold to mode-locked operation is crossed. We use a fast detector and a spectrum analyzer to measure the beat frequency between neighboring modes. This simple method to determine the laser cavity free spectral range yields a value of 345(1) MHz.

It is remarkable that the mode locking arises when tuning the phase-matching temperature to colder-than-optimal values. In analogy to standard Kerr-lens mode locking, the χ(2) : χ(2) process requires an additional intracavity element which modifies the round-trip gain or loss as a function of the power-dependent cavity mode size. This can be realized by the gain medium, cf. Fig. 1. As we presented in Section 2, the pump-to-cavity mode overlap has been carefully optimized in the cw regime. However, an ABCD-matrix-based cavity mode calculation reveals that the beam waist in the Nd:YVO4 only changes monotonously when crossing over from negative to positive focal powers in the ppKTP. Thus, the induced change in gain or loss should be less favorable whenever the lensing departs from the optimized value. We note that Zondy et al.[20

20. J. Zondy, F. Camargo, T. Zanon, V. Petrov, and N. Wetter, “Observation of strong cascaded Kerr-lens dynamics in an optimally-coupled cw intracavity frequency-doubled Nd:YLF ring laser,” Opt. Express 18, 4796–4815 (2010) [CrossRef] [PubMed] .

] argue that pulsed operation should occur whenever there exists a power-dependent gain-loss mechanism, whichever is the sign of the focal power in the ppKTP. Furthermore, we also note that in our simple analysis, we do not take into account different Kerr-like and thermal lenses that may occur in the intra-cavity elements other than the laser and nonlinear crystals. Using the temperature-dependent Sellmeier equations of [22

22. K. Fradkin, A. Arie, A. Skliar, and G. Rosenman, “Tunable midinfrared source by difference frequency generation in bulk periodically poled KTiOPO4,” Appl. Phys. Lett. 74, 914–916 (1999) [CrossRef] .

, 23

23. S. Emanueli and A. Arie, “Temperature-dependent dispersion equations for KTiOPO4 and KTiOAsO4,” Appl. Opt. 42, 6661–6665 (2003) [CrossRef] [PubMed] .

], we get dephasing parameters of β(Tlow) = 8.8(1) and β(Thigh) = −18.5(1), resulting in a single-pass efficiency η(T) reduced to less than 5% of the maximum value.

The laser can be tuned continuously using a piezoelectric transducer (PZT), upon which mirror M2 is glued upon. This allows mode-hope free scans of the 671-nm output frequency over more than 6 GHz. For the resonated fundamental light this amounts to about ten times the laser cavity free spectral range, a typical behavior of ICSHG lasers with self-suppressed mode hopping [26

26. K. I. Martin, W. A. Clarkson, and D. C. Hanna, “Self-suppression of axial mode hopping by intracavity second-harmonic generation,” Opt. Lett. 22, 375–377 (1997) [CrossRef] [PubMed] .

, 27

27. S. Helmfrid and K. Tatsuno, “Stable single-mode operation of intracavity-doubled diode-pumped Nd:YVO4 lasers: theoretical study,” J. Opt. Soc. Am. B 11, 436–445 (1994) [CrossRef] .

]. We perform Doppler-free saturated absorption spectroscopy on a lithium vapor cell described previously in [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

], see Fig. 6. In Fig. 6(a) we show a sample scan over the full Doppler-broadened lithium-6 D1 line. The ground-state hyperfine structure is clearly resolved. We phase-modulate the probe beam at 20 MHz using an electro-optic modulator, and then use a commercial lock-in amplifier to generate a dispersive error signal as presented in Fig. 6(b). We can access all D-line transitions of both naturally abundant lithium isotopes, and the full ground state hyperfine structure is resolved.

Fig. 6 Doppler-free saturated absorption spectroscopy of the lithium D-lines. (a) Sample scan over the entire 6Li D1 Doppler-broadened absorption peak. The inset shows the sub-Doppler features. Similar spectra are obtained for all lithium D lines. (b) Error signals of all lithium D-line transitions, generated by phase modulation spectroscopy. These signals provide an excellent reference for frequency-locking of the laser.

The laser linewidth was estimated by slowly scanning the emission frequency over the D1-line of lithium-6. From the observed peak-to-peak noise in the linear part of the error signal we obtain an upper limit of 1 MHz for the laser linewidth. For frequency-locking the laser, we feed the error signal in a home-made proportional-integral controller. The regulator signal is split internally in a low-frequency part, sent to the slow PZT (M2) used for scanning the laser, and a high-frequency part, sent directly to a fast PZT glued between M4 and its mount. The system can easily stay locked for a full day, even in presence of significant acoustic noise coupled to the optical table. We note that due to the self suppression of mode hopping, it can be time consuming to optimize the laser output parameters after switch-off.

5. Conclusion

In conclusion, we presented the design and the performance of an all-solid-state, intracavity-frequency-doubled single-mode laser source. The ring laser emits up to 2.5 W of unidirectional multifrequency radiation at the fundamental wavelength, and we determine the parameters necessary for efficient ICSHG. Starting from this well-characterized infrared system, the optimized ICSHG yields up to 2.1 W of single-mode, frequency-stabilized output at 671 nm. We discussed a simple theory describing the output power of an intra-cavity frequency-doubled laser. Within the region of efficient nonlinear conversion, the theory describes our experimental findings well. We furthermore presented a measurement of the emission spectrum of both the fundamental and the ICSHG source, displaying around 1.8 W of output power at the lithium D-lines. By comparing both emission spectra, we maximally obtain 88% of the fundamental power at 671 nm, and typically more than 80%. This demonstrates a very efficient ICSHG process across the full emission spectrum. We observe nonlinear-Kerr-lens mode-locked operation when detuning the ppKTP temperature sufficiently far from the phase matching condition. Furthermore, we discussed the fine-tunability of the source by presenting Doppler-free saturated absorption spectra of all lithium D-line transitions. The 671-nm output can be mode-hop-free scanned over more than 6 GHz, which corresponds to more than ten times the laser cavity free spectral range. As compared to the most powerful conventional design [5

5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

], our laser is an improvement by more than a factor of three in terms of output power. In comparison to commercial semiconductor tapered amplifier designs, we gain a factor of four in terms of output power and keep a beam quality close to the diffraction limit. Compared to vertical external cavity surface emitting laser (VECSELs) designs [33

33. J. Hastie, S. Calvez, M. Dawson, T. Leinonen, A. Laakso, J. Lyytikinen, and M. Pessa, “High power CW red VECSEL with linearly polarized TEM00 output beam,” Opt. Express 13, 77–81 (2005) [CrossRef] [PubMed] .

], our laser is five times more powerful together with a linewidth in the 100-kHz range.

The output power of our source is largely sufficient for creating all the laser beams needed for an ultracold atoms experiment. However, for other applications such as atom interferometry, even more power might be helpful and we will briefly discuss how this can possibly be established. An obvious way is to use a different cavity geometry allowing for two-sided pumping of the active medium. Convex pump couplers can compensate the thermal lens close to the laser crystal, which has proved very efficient in high-power resonators, see for instance [17

17. F. Lenhardt, M. Nittmann, T. Bauer, J. Bartschke, and J. L’huillier, “High-power 888-nm-pumped Nd:YVO4 1342-nm oscillator operating in the TEM00 mode,” Appl. Phys. B 96, 803–807 (2009) [CrossRef] .

]. A large part of the output power limitations stems from the additional intracavity elements, such as the Faraday rotator. Thus, injection locking of an amplifier consisting of an empty high-power resonator such as presented in [17

17. F. Lenhardt, M. Nittmann, T. Bauer, J. Bartschke, and J. L’huillier, “High-power 888-nm-pumped Nd:YVO4 1342-nm oscillator operating in the TEM00 mode,” Appl. Phys. B 96, 803–807 (2009) [CrossRef] .

] could deliver tens of watts of single-frequency fundamental light. At these elevated power levels, efficient single-pass frequency doubling of 1342-nm radiation has been demonstrated [34

34. F. Lenhardt, A. Nebel, R. Knappe, M. Nittmann, J. Bartschke, and J. A. L’huillier, “Efficient single-pass second harmonic generation of a continuous wave Nd:YVO4- laser at 1342 nm using MgO:ppLN,” CLEO 2010, CThEE5.

], the implementation of which considerably relaxes the complexity of multi-cavity designs.

Acknowledgments

We acknowledge the group of Jacques Vigué for discussions and exchange of material, and Carlota Canalias for providing the ppKTP. The authors wish to thank Colin Parker, Peter Scherpelz and Shih-Kuang Tung for helpful comments on the manuscript. We acknowledge support from Région Ile de France (IFRAF), EU (ERC advanced grant FERLODIM), and Institut Universitaire de France.

References and links

1.

S. Giorgini, L. P. Pitaevskii, and S. Stringari, “Theory of ultracold atomic Fermi gases,” Rev. Mod. Phys. 80, 1215–1274 (2008) [CrossRef] .

2.

C. Chin, R. Grimm, P. Julienne, and E. Tiesinga, “Feshbach resonances in ultracold gases,” Rev. Mod. Phys. 82, 1225–1286 (2010) [CrossRef] .

3.

F. Hou, L. Yu, X. Jia, Y. Zheng, C. Xie, and K. Peng, “Experimental generation of optical non-classical states of light with 1.34 μm wavelength,” Eur. Phys. J. D 62, 433–437 (2011) [CrossRef] .

4.

F. Camargo, T. Zanon-Willette, T. Badr, N. Wetter, and J. Zondy, “Tunable single-frequency Nd:YVO4 BiB3O6 ring laser at 671 nm,” IEEE J. Quantum Elect. 46, 804–809 (2010) [CrossRef] .

5.

U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B 106, 25–36 (2012) [CrossRef] .

6.

D. Fernandes, F. Sievers, N. Kretzschmar, S. Wu, C. Salomon, and F. Chevy, “Sub-doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses,” Europhys. Lett. 100, 63001 (2012) [CrossRef] .

7.

A. Miffre, M. Jacquey, M. Büchner, G. Trénec, and J. Vigué, “Atom interferometry measurement of the electric polarizability of lithium,” Eur. Phys. J. D 38, 353–365 (2006) [CrossRef] .

8.

H. Müller, S.-w. Chiow, Q. Long, S. Herrmann, and S. Chu, “Atom interferometry with up to 24-photon-momentum-transfer beam splitters,” Phys. Rev. Lett. 100, 180405 (2008) [CrossRef] [PubMed] .

9.

I. E. Olivares, A. E. Duarte, E. A. Saravia, and F. J. Duarte, “Lithium isotope separation with tunable diode lasers,” Appl. Opt. 41, 2973–2977 (2002) [CrossRef] [PubMed] .

10.

S. A. Payne, L. K. Smith, R. J. Beach, B. H. T. Chai, J. H. Tassano, L. D. DeLoach, W. L. Kway, R. W. Solarz, and W. F. Krupke, “Properties of Cr:LiSrAIF6 crystals for laser operation,” Appl. Opt. 33, 5526 (1994) [CrossRef] [PubMed] .

11.

L. McDonagh, R. Wallenstein, R. Knappe, and A. Nebel, “High-efficiency 60 W TEM00 Nd:YVO4 oscillator pumped at 888 nm,” Opt. Lett. 31, 3297–3299 (2006) [CrossRef] [PubMed] .

12.

G. Trénec, W. Volondat, O. Cugat, and J. Vigué, “Permanent magnets for Faraday rotators inspired by the design of the magic sphere,” Appl. Opt. 50, 4788–4797 (2011) [CrossRef] [PubMed] .

13.

P. Laporta and M. Brussard, “Design criteria for mode size optimization in diode-pumped solid-state lasers,” IEEE J. Quantum Elect. 27, 2319–2326 (1991) [CrossRef] .

14.

Y. F. Chen, T. M. Huang, C. F. Kao, C. L. Wang, and S. C. Wang, “Optimization in scaling fiber-coupled laser-diode end-pumped lasers to higher power: influence of thermal effect,” IEEE J. Quantum Elect. 33, 1424–1429 (1997) [CrossRef] .

15.

W. Rigrod, “Gain saturation and output power of optical masers,” J. Appl. Phys. 34, 2602–2609 (1963) [CrossRef] .

16.

E. Khazanov, N. Andreev, A. Mal’shakov, O. Palashov, A. Poteomkin, A. Sergeev, A. Shaykin, V. Zelenogorsky, I. Ivanov, R. Amin, G. Mueller, D.B. Tanner, and D.H. Reitze, “Compensation of thermally induced modal distortions in Faraday isolators,” IEEE J. Quantum Elect. 40, 1500–1510 (2004) [CrossRef] .

17.

F. Lenhardt, M. Nittmann, T. Bauer, J. Bartschke, and J. L’huillier, “High-power 888-nm-pumped Nd:YVO4 1342-nm oscillator operating in the TEM00 mode,” Appl. Phys. B 96, 803–807 (2009) [CrossRef] .

18.

R. Polloni and O. Svelto, “Optimum coupling for intracavity second harmonic generation,” Quantum Electronics, IEEE J. Quantum Elect. 4, 528–530 (1968) [CrossRef] .

19.

R. Smith, “Theory of intracavity optical second-harmonic generation,” IEEE J. Quantum Elect. 6, 215–223 (1970) [CrossRef] .

20.

J. Zondy, F. Camargo, T. Zanon, V. Petrov, and N. Wetter, “Observation of strong cascaded Kerr-lens dynamics in an optimally-coupled cw intracavity frequency-doubled Nd:YLF ring laser,” Opt. Express 18, 4796–4815 (2010) [CrossRef] [PubMed] .

21.

G. D. Boyd and D. A. Kleinman, “Parametric interaction of focused gaussian light beams,” J. Appl. Phys. 39, 3597–3639 (1968) [CrossRef] .

22.

K. Fradkin, A. Arie, A. Skliar, and G. Rosenman, “Tunable midinfrared source by difference frequency generation in bulk periodically poled KTiOPO4,” Appl. Phys. Lett. 74, 914–916 (1999) [CrossRef] .

23.

S. Emanueli and A. Arie, “Temperature-dependent dispersion equations for KTiOPO4 and KTiOAsO4,” Appl. Opt. 42, 6661–6665 (2003) [CrossRef] [PubMed] .

24.

M. Peltz, U. Bäder, A. Borsutzky, R. Wallenstein, J. Hellström, H. Karlsson, V. Pasiskevicius, and F. Laurell, “Optical parametric oscillators for high pulse energy and high average power operation based on large aperture periodically poled KTP and RTA,” Appl. Phys. B 73, 663–670 (2001) [CrossRef] .

25.

U. Eismann, “A novel all-solid-state laser source for lithium atoms and three-body recombination in the unitary Bose gas,” Ph.D. thesis, Université Pierre et Marie Curie – Paris VI, http://tel.archives-ouvertes.fr/tel-00702865/(2012).

26.

K. I. Martin, W. A. Clarkson, and D. C. Hanna, “Self-suppression of axial mode hopping by intracavity second-harmonic generation,” Opt. Lett. 22, 375–377 (1997) [CrossRef] [PubMed] .

27.

S. Helmfrid and K. Tatsuno, “Stable single-mode operation of intracavity-doubled diode-pumped Nd:YVO4 lasers: theoretical study,” J. Opt. Soc. Am. B 11, 436–445 (1994) [CrossRef] .

28.

W. Leeb, “Losses introduced by tilting intracavity etalons,” Appl. Phys. A 6, 267–272 (1975).

29.

L. Rothman, I. Gordon, A. Barbe, D. Benner, P. Bernath, M. Birk, V. Boudon, L. Brown, A. Campargue, J.-P. Champion, K. Chance, L. Coudert, V. Dana, V. Devi, S. Fally, J.-M. Flaud, R. Gamache, A. Goldman, D. Jacquemart, I. Kleiner, N. Lacome, W. Lafferty, J.-Y. Mandin, S. Massie, S. Mikhailenko, C. Miller, N. Moazzen-Ahmadi, O. Naumenko, A. Nikitin, J. Orphal, V. Perevalov, A. Perrin, A. Predoi-Cross, C. Rinsland, M. Rotger, M. imekov, M. Smith, K. Sung, S. Tashkun, J. Tennyson, R. Toth, A. Vandaele, and J. V. Auwera, “The HITRAN 2008 molecular spectroscopic database,” J. Quant. Spectrosc. Ra. 110, 533 – 572 (2009) [CrossRef] .

30.

R. DeSalvo, D. J. Hagan, M. Sheik-Bahae, G. Stegeman, E. W. V. Stryland, and H. Vanherzeele, “Self-focusing and self-defocusing by cascaded second-order effects in KTP,” Opt. Lett. 17, 28–30 (1992) [CrossRef] [PubMed] .

31.

S. Holmgren, V. Pasiskevicius, and F. Laurell, “Generation of 2.8-ps pulses by mode-locking a Nd:GdVO4 laser with defocusing cascaded kerr lensing in periodically poled KTP,” Opt. Express 13, 5270–5278 (2005) [CrossRef] [PubMed] .

32.

C. Schäfer, C. Fries, C. Theobald, and J. A. L’huillier, “Parametric Kerr lens mode-locked, 888 nm pumped Nd:YVO4 laser,” Opt. Lett. 36, 2674–2676 (2011) [CrossRef] [PubMed] .

33.

J. Hastie, S. Calvez, M. Dawson, T. Leinonen, A. Laakso, J. Lyytikinen, and M. Pessa, “High power CW red VECSEL with linearly polarized TEM00 output beam,” Opt. Express 13, 77–81 (2005) [CrossRef] [PubMed] .

34.

F. Lenhardt, A. Nebel, R. Knappe, M. Nittmann, J. Bartschke, and J. A. L’huillier, “Efficient single-pass second harmonic generation of a continuous wave Nd:YVO4- laser at 1342 nm using MgO:ppLN,” CLEO 2010, CThEE5.

OCIS Codes
(140.3480) Lasers and laser optics : Lasers, diode-pumped
(140.4050) Lasers and laser optics : Mode-locked lasers
(190.2620) Nonlinear optics : Harmonic generation and mixing
(020.1335) Atomic and molecular physics : Atom optics
(020.3320) Atomic and molecular physics : Laser cooling

ToC Category:
Atomic and Molecular Physics

History
Original Manuscript: January 16, 2013
Revised Manuscript: March 7, 2013
Manuscript Accepted: March 19, 2013
Published: April 4, 2013

Citation
U. Eismann, A. Bergschneider, F. Sievers, N. Kretzschmar, C. Salomon, and F. Chevy, "2.1-watts intracavity-frequency-doubled all-solid-state light source at 671 nm for laser cooling of lithium," Opt. Express 21, 9091-9102 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-7-9091


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References

  1. S. Giorgini, L. P. Pitaevskii, and S. Stringari, “Theory of ultracold atomic Fermi gases,” Rev. Mod. Phys.80, 1215–1274 (2008). [CrossRef]
  2. C. Chin, R. Grimm, P. Julienne, and E. Tiesinga, “Feshbach resonances in ultracold gases,” Rev. Mod. Phys.82, 1225–1286 (2010). [CrossRef]
  3. F. Hou, L. Yu, X. Jia, Y. Zheng, C. Xie, and K. Peng, “Experimental generation of optical non-classical states of light with 1.34 μm wavelength,” Eur. Phys. J. D62, 433–437 (2011). [CrossRef]
  4. F. Camargo, T. Zanon-Willette, T. Badr, N. Wetter, and J. Zondy, “Tunable single-frequency Nd:YVO4 BiB3O6 ring laser at 671 nm,” IEEE J. Quantum Elect.46, 804–809 (2010). [CrossRef]
  5. U. Eismann, F. Gerbier, C. Canalias, A. Zukauskas, G. Trénec, J. Vigué, F. Chevy, and C. Salomon, “An all-solid-state laser source at 671 nm for cold-atom experiments with lithium,” Appl. Phys. B106, 25–36 (2012). [CrossRef]
  6. D. Fernandes, F. Sievers, N. Kretzschmar, S. Wu, C. Salomon, and F. Chevy, “Sub-doppler laser cooling of fermionic 40K atoms in three-dimensional gray optical molasses,” Europhys. Lett.100, 63001 (2012). [CrossRef]
  7. A. Miffre, M. Jacquey, M. Büchner, G. Trénec, and J. Vigué, “Atom interferometry measurement of the electric polarizability of lithium,” Eur. Phys. J. D38, 353–365 (2006). [CrossRef]
  8. H. Müller, S.-w. Chiow, Q. Long, S. Herrmann, and S. Chu, “Atom interferometry with up to 24-photon-momentum-transfer beam splitters,” Phys. Rev. Lett.100, 180405 (2008). [CrossRef] [PubMed]
  9. I. E. Olivares, A. E. Duarte, E. A. Saravia, and F. J. Duarte, “Lithium isotope separation with tunable diode lasers,” Appl. Opt.41, 2973–2977 (2002). [CrossRef] [PubMed]
  10. S. A. Payne, L. K. Smith, R. J. Beach, B. H. T. Chai, J. H. Tassano, L. D. DeLoach, W. L. Kway, R. W. Solarz, and W. F. Krupke, “Properties of Cr:LiSrAIF6 crystals for laser operation,” Appl. Opt.33, 5526 (1994). [CrossRef] [PubMed]
  11. L. McDonagh, R. Wallenstein, R. Knappe, and A. Nebel, “High-efficiency 60 W TEM00 Nd:YVO4 oscillator pumped at 888 nm,” Opt. Lett.31, 3297–3299 (2006). [CrossRef] [PubMed]
  12. G. Trénec, W. Volondat, O. Cugat, and J. Vigué, “Permanent magnets for Faraday rotators inspired by the design of the magic sphere,” Appl. Opt.50, 4788–4797 (2011). [CrossRef] [PubMed]
  13. P. Laporta and M. Brussard, “Design criteria for mode size optimization in diode-pumped solid-state lasers,” IEEE J. Quantum Elect.27, 2319–2326 (1991). [CrossRef]
  14. Y. F. Chen, T. M. Huang, C. F. Kao, C. L. Wang, and S. C. Wang, “Optimization in scaling fiber-coupled laser-diode end-pumped lasers to higher power: influence of thermal effect,” IEEE J. Quantum Elect.33, 1424–1429 (1997). [CrossRef]
  15. W. Rigrod, “Gain saturation and output power of optical masers,” J. Appl. Phys.34, 2602–2609 (1963). [CrossRef]
  16. E. Khazanov, N. Andreev, A. Mal’shakov, O. Palashov, A. Poteomkin, A. Sergeev, A. Shaykin, V. Zelenogorsky, I. Ivanov, R. Amin, G. Mueller, D.B. Tanner, and D.H. Reitze, “Compensation of thermally induced modal distortions in Faraday isolators,” IEEE J. Quantum Elect.40, 1500–1510 (2004). [CrossRef]
  17. F. Lenhardt, M. Nittmann, T. Bauer, J. Bartschke, and J. L’huillier, “High-power 888-nm-pumped Nd:YVO4 1342-nm oscillator operating in the TEM00 mode,” Appl. Phys. B96, 803–807 (2009). [CrossRef]
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