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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 15, Iss. 20 — Oct. 1, 2007
  • pp: 13451–13456
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Dual-wavelength generation by vertical external cavity surface-emitting laser

Tomi Leinonen, Sanna Ranta, Antti Laakso, Yuri Morozov, Mika Saarinen, and Markus Pessa  »View Author Affiliations


Optics Express, Vol. 15, Issue 20, pp. 13451-13456 (2007)
http://dx.doi.org/10.1364/OE.15.013451


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Abstract

A high-power dual-wavelength AlGaInAs / GaAs laser operating in a vertical external-cavity surface emitting geometry, grown by molecular beam epitaxy, is reported. The active regions of the laser are separated by an optical long-wave-pass filter to prevent absorption of short-wavelength radiation in the long-wavelength gain area. The maximum output power achieved at 15 °C was 0.75 W at λ ≈ 966 nm and 1.38 W at λ ≈ 1047 nm for the pump power of 21.2 W.

© 2007 Optical Society of America

1. Introduction

Despite the success of quantum-cascade lasers in the mid (MIR)- and far-infrared (FIR) spectral ranges [1

1. M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Illegems, E. Gini, and H. Melchior, “Continuous wave operation of a mid-infrared semiconductor laser at room temperature,” Science 295, 301–305 (2002). [CrossRef] [PubMed]

], room-temperature continuous-wave operation at the wavelengths longer than 10 μm seems to be unattainable in the near future. Therefore, alternative approaches to achieve MIR (or FIR) radiation should be examined. Nonlinear optical three-wave interaction, accompanying by generation of difference frequency in these ranges can be regarded as an attractive approach [2

2. O. Levi, T.J. Pinguet, T. Skauli, L.A. Eyres, K.R. Parameswaran, J.S. Harris, M.M. Fejer, TJ. Kulp, S.E. Bisson, B. Gerard, E. Lallier, and L. Becouarn, “Difference frequency generation of 8-μm radiation in orientation-patterned GaAs,” Opt. Lett. 27, 2091–2093 (2002). [CrossRef]

,3

3. D. Zheng, l.A Gordon, Y.S. Wu, R.S. Feigelson, M.M. Fejer, R.L. Byer, and K.L. Vodopyanov, “16-μm infrared generation by difference-frequency mixing in diffusion-bonded-stacked GaAs,” Opt. Lett. 23, 1010–1012 (1998). [CrossRef]

]. To achieve an effective frequency-down conversion it is desirable to have a laser launching simultaneously two parent wavelengths. Moreover, the optimal device should emit both the wavelengths co-axially with total spatial overlap at high light power. In addition, an external cavity allowing for the use of a nonlinear crystal would be desirable. A dual-wavelength vertical external cavity surface-emitting laser (VECSEL) is an almost perfect device to fulfil these requirements. Intracavity difference frequency generation, instead, achieved by mixing of radiation from two separate lasers always needs complex equipment, including a servocontrol external cavity frequency [4

4. U. Simon, S. Waltman, I. Loa, F.K. Tittel, and L Hollberg, “External-cavity difference-frequency source near 3.2 μm, based on combining a tunable diode laser with a diode-pumped Nd:YAG laser in AgGaS2,” J. Opt. Soc. Am. B 12, 323–327 (1995). [CrossRef]

]. In sharp contrast to this, in a dual-wavelength VECSEL, both wavelengths are modes of the cavity and remain enhanced by the cavity, irrespective of slight variations in resonance frequencies, thus enhancing the efficiency of nonlinear three-wave interaction.

In our laser [5

5. T. Leinonen, Yu. A. Morozov, A. Härkönen, and M. Pessa, ”Vertical external-cavity surface-emitting laser for dual-wavelength generation,” IEEE Photon. Technol. Lett. 17, 2508–2510 (2005). [CrossRef]

] the absorption of λs was reduced by placing the λL quantum wells (QWs) at the nodes of the λs standing wave pattern. This approach worked quite well, but due to slight unavoidable inaccuracies in growth of the laser structure and in modelling the device, residual absorption led to unstable operation of the laser under high-power emission [16

16. Y. A. Morozov, T. Leinonen, A. Härkönen, and M. Pessa, “Simultaneous Dual-Wavelength Emission from Vertical External-Cavity Surface-Emitting Laser: a Numerical Modeling,” IEEE J. Quantum Electron. 42, 1055–1061 (2006). [CrossRef]

]. The independent pumping of the QWs operating at λs and λL was achieved by dividing the active region into the subsections with the carrier blocking layers.

Recently, successful sum-frequency generation was obtained by our device [17

17. A. Härkönen, J. Rautiainen, T. Leinonen, Y.A. Morozov, L. Orsila, M. Guina, M. Pessa, and O.G. Okhot-nikov, “Intracavity sum-frequency generation in dual-wavelength semiconductor disk laser,” IEEE Photon. Technol. Lett. 19, 1550–1552 (2007). [CrossRef]

], confirming the potential of dual-wavelength VECSEL for nonlinear frequency conversion.

A linearly polarized dual-wavelength operation at a multiple watt power level by an optically pumped VECSEL utilizing a tilted intracavity Fabry-Perot etalon and a Brewster window has been reported [18

18. L. Fan, M. Fallahi, J. Hader, A.R. Zakharian, J.V. Moloney, W. Stolz, S.W. Koch, R. Bedford, and J.T. Murray, “Linearly polarized dual-wavelength vertical-external-cavity surface-emitting laser,” Appl. Phys. Lett. 90, 181124 (2007). [CrossRef]

]. However, Δλ achieved was only about 2.1 nm.

2. Device design

The laser was designed to be used as a source for intracavity difference frequency generation with a quasi-phase-matched GaAs nonlinear crystal as in [2

2. O. Levi, T.J. Pinguet, T. Skauli, L.A. Eyres, K.R. Parameswaran, J.S. Harris, M.M. Fejer, TJ. Kulp, S.E. Bisson, B. Gerard, E. Lallier, and L. Becouarn, “Difference frequency generation of 8-μm radiation in orientation-patterned GaAs,” Opt. Lett. 27, 2091–2093 (2002). [CrossRef]

,3

3. D. Zheng, l.A Gordon, Y.S. Wu, R.S. Feigelson, M.M. Fejer, R.L. Byer, and K.L. Vodopyanov, “16-μm infrared generation by difference-frequency mixing in diffusion-bonded-stacked GaAs,” Opt. Lett. 23, 1010–1012 (1998). [CrossRef]

]. Therefore, the wavelengths were chosen to fit the transparency window of the nonlinear crystal, to ensure good carrier confinement for λS QWs, and to control lattice strain introduced in the λL QWs. The maximum Δλ is limited by the last two factors, whereas for this particular design, the minimum Δλ is limited by the slope of the intracavity filter. Within these limits, Δλmax and Δλmin, the two wavelengths can be chosen arbitrarily. In order to avoid absorption of λS in the λL QWs, the gain sections for λS and λL were spatially separated. The λS QWs were located close to the surface of the device, while λL QWs were situated deeper in the structure. A long-wave-pass filter, which consisted of alternating 81-nm thick AlAs and 72-nm Al0.30GaAs layers, was placed between the two gain regions to prevent λS from penetrating into the λL QW region. The computed electric fields inside the layer structure are displayed in Fig. 1. The stop-band of the long-wave-pass filter was chosen to have λL at one of the reflection minima on the λL side of the filter.

Fig. 1. Index profile (continuous line) of the dual-wavelength VECSEL along with the electric field of λS (dashed line) and λL (dotted line).

The λS and λL gain sections contained six compressively strained In0.14Ga0.86As QWs and seven strained In0.25Ga0.75As QWs, respectively, situated in the anti-nodes of the cavity standing wave to ensure good coupling between the optical field and the QWs. To cancel lattice strain induced by the QWs, the top active region had two strain-compensating layers of GaAs0.70P0.30 of 20 nm in thickness (see Fig. 1). The bottom active region had two 10-nm and three 20-nm thick GaAs0.70P0.30 layers. Carrier transport across the GaAs0.70P0.30 layers was blocked by high potential-energy barriers, which were automatically induced by the band-gap discontinuity at the GaAs0.70P0.30/GaAs heterojunctions. The locations of the GaAs0.70P0.30 layers were chosen to equalize absorption of pump light per QW.

3. Device fabrication and measurement setup

The layer structure was grown by molecular beam epitaxy (MBE) on a 2” n-GaAs (100) substrate after growth-rate calibrations under similar growth conditions to those given in [4

4. U. Simon, S. Waltman, I. Loa, F.K. Tittel, and L Hollberg, “External-cavity difference-frequency source near 3.2 μm, based on combining a tunable diode laser with a diode-pumped Nd:YAG laser in AgGaS2,” J. Opt. Soc. Am. B 12, 323–327 (1995). [CrossRef]

]. A close agreement between the simulated reflectance and the measured reflectance is seen in Fig. 2. The largest deviations appearing near the absorption peaks of the QWs and near the resonances inside the structure are due to slight uncertainties in absorption coefficients and a red-shift chosen for computer simulations.

Fig. 2. Measured (continuous line) and simulated (dashed line) reflectivity spectra of the dual-wavelength VECSEL structure.

A 2.5 × 2.5 mm2 chip of the gain material was capillary bonded to a natural diamond heat spreader. The V-shape VECSEL cavity setup with a 1 % output coupler was identical to the one published in [5

5. T. Leinonen, Yu. A. Morozov, A. Härkönen, and M. Pessa, ”Vertical external-cavity surface-emitting laser for dual-wavelength generation,” IEEE Photon. Technol. Lett. 17, 2508–2510 (2005). [CrossRef]

]. The pump wavelength was 808 nm.

4. Results and discussion

The laser mount temperature was kept at 15 °C in all measurements. The output power (Pout) per laser beam was studied by means of a short-wave-pass filter. The threshold pump power was 2.3 W for λL and 5.4 W for λS (see Fig. 3). The maximum conversion efficiency of 10.8 % was achieved at the pump power of 16 W, corresponding to Pout ≈ 0.5 W and 1.2 W at λS and λL, respectively. The higher threshold and the lower slope efficiency for λS were likely due to the smaller number of the λS QWs and a weaker carrier confinement than those for λL.

The long wavelength, λL, reached a thermal roll-over condition before λS did so (which happened at the pump power of 19.4 W) because of higher thermal impedance caused by the optical long-wave-pass filter in the heat dissipation pathway. Therefore, the maximum simultaneous Pout was 0.75 W for λS and 1.38 W for λL at the pump power of 21.2 W.

Figure 4 shows the emission spectrum at the pump power of 17.7 W. The spectrum is made up of two peaks, one at λ ≈ 966 nm, the other at 1047 nm (record large Δλ ≈ 81nm for VECSELs). The beam quality factor M2 was 1.38 and 1.51 in the lateral directions (at the pump power of 16 W), measured by a scanning slit device with 5-μm wide slits and a silicon detector.

Fig. 3. Output power versus pump power for λS (dashed line) and for λL (dotted line).

Fig. 4. Output spectrum of the dual-wavelength VECSEL.

5. Conclusions

Acknowledgment

This work was supported, in part, by The Academy of Finland within Projects #115810 and #109080 and by the Ministry of Education within a national NanoPhotonics Program.

References and links

1.

M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Illegems, E. Gini, and H. Melchior, “Continuous wave operation of a mid-infrared semiconductor laser at room temperature,” Science 295, 301–305 (2002). [CrossRef] [PubMed]

2.

O. Levi, T.J. Pinguet, T. Skauli, L.A. Eyres, K.R. Parameswaran, J.S. Harris, M.M. Fejer, TJ. Kulp, S.E. Bisson, B. Gerard, E. Lallier, and L. Becouarn, “Difference frequency generation of 8-μm radiation in orientation-patterned GaAs,” Opt. Lett. 27, 2091–2093 (2002). [CrossRef]

3.

D. Zheng, l.A Gordon, Y.S. Wu, R.S. Feigelson, M.M. Fejer, R.L. Byer, and K.L. Vodopyanov, “16-μm infrared generation by difference-frequency mixing in diffusion-bonded-stacked GaAs,” Opt. Lett. 23, 1010–1012 (1998). [CrossRef]

4.

U. Simon, S. Waltman, I. Loa, F.K. Tittel, and L Hollberg, “External-cavity difference-frequency source near 3.2 μm, based on combining a tunable diode laser with a diode-pumped Nd:YAG laser in AgGaS2,” J. Opt. Soc. Am. B 12, 323–327 (1995). [CrossRef]

5.

T. Leinonen, Yu. A. Morozov, A. Härkönen, and M. Pessa, ”Vertical external-cavity surface-emitting laser for dual-wavelength generation,” IEEE Photon. Technol. Lett. 17, 2508–2510 (2005). [CrossRef]

6.

K.R. Poguntke, J.B.D. Soole, A. Scherer, H.P. LeBlanc, C. Caneau, R Bhat, and M.A Koza, ”Simultaneous multiple wavelength operation of a multistripe array grating integrated cavity laser,” Appl. Phys. Lett. 62, 2024–2026 (1993). [CrossRef]

7.

C.L Wang, Y.H. Chuang, and C.L. Pan, ”Two-wavelength interferometer based on a two-color laser diode array and the second-order correlation technique,” Opt. Lett. 20, 1071–1073 (1995). [CrossRef] [PubMed]

8.

C.L. Wang and C.L. Pan, ”Tunable multiterahertz beat signal generation from a two-wavelength laser-diode array,” Opt. Lett. 20, 1292–1294 (1995). [CrossRef] [PubMed]

9.

C.-C. Huang, C.-H. Cheng, Y.-S. Su, and C.-F. Lin, ”174-nm mode spacing in dual-wavelength semicon-fuctor laser using nonidentical InGaAsP quantum wells,” IEEE Photon. Technol. Lett. 16, 371–373 (2004). [CrossRef]

10.

C.-F. Lin, M.-J. Chen, and B.-L Lee, ”Wide-range tunable dual-wavelength semiconductor laser using asymmetric dual quantum wells,” IEEE Photon. Technol. Lett. 10, 1208–1210 (1998). [CrossRef]

11.

P. Pellandini, R. Stanley, R. Houdre, U. Oesterle, and M. Ilegems, ”Dual-wavelength laser emission from a coupled semiconductor microcavity,” Appl. Phys. Lett. 71, 864–866 (1997). [CrossRef]

12.

P. Michler, M. Hilpert, and G. Reiner, ”Dynamics of dual-wavelength emission from a coupled semiconductor microcavity laser,” Appl. Phys. Lett. 70, 2073–2075 (1997). [CrossRef]

13.

M. Brunner, K. Gulden, R. Hovel, M. Moser, J.-F. Carlin, R.P. Stanley, and M. Ilegems, ”Continuous-wave dual-wavelength lasing in a two-section vertical-cavity laser,” IEEE Photon. Technol. Lett. 12, 1316–1318 (2000). [CrossRef]

14.

D.M. Grasso and K.D. Choquette, ”Threshold and modal characteristics of composite-resonator vertical-cavity lasers,” IEEE J. Quantum Electron. 39, 1526–1530 (2003). [CrossRef]

15.

V. Badilita, J.-F. Carlin, M. Ilegems, and K. Panajotov, ”Rate-equation model for coupled-cavity surface-emitting lasers,” IEEE J. Quantum Electron. 40, 1646–1656 (2004). [CrossRef]

16.

Y. A. Morozov, T. Leinonen, A. Härkönen, and M. Pessa, “Simultaneous Dual-Wavelength Emission from Vertical External-Cavity Surface-Emitting Laser: a Numerical Modeling,” IEEE J. Quantum Electron. 42, 1055–1061 (2006). [CrossRef]

17.

A. Härkönen, J. Rautiainen, T. Leinonen, Y.A. Morozov, L. Orsila, M. Guina, M. Pessa, and O.G. Okhot-nikov, “Intracavity sum-frequency generation in dual-wavelength semiconductor disk laser,” IEEE Photon. Technol. Lett. 19, 1550–1552 (2007). [CrossRef]

18.

L. Fan, M. Fallahi, J. Hader, A.R. Zakharian, J.V. Moloney, W. Stolz, S.W. Koch, R. Bedford, and J.T. Murray, “Linearly polarized dual-wavelength vertical-external-cavity surface-emitting laser,” Appl. Phys. Lett. 90, 181124 (2007). [CrossRef]

19.

A.C. Tropper, H.D. Foreman, A. Carnache, K.G. Wilcox, and S.H. Hoogland, ”Vertical-external-cavity semiconductor lasers,” J. Phys. D 37, R75–R85 (2004). [CrossRef]

20.

J.-M. Hopkins, A. J. Maclean, D. Burns, E. Riis, N. Schulz, M. Rattunde, C. Manz, K. Köhler, and J. Wagner, “Tunable, Single-frequency, Diode-pumped 2.3μm VECSEL,” Opt. Express 15, 8212–8217 (2007). [CrossRef] [PubMed]

OCIS Codes
(140.3070) Lasers and laser optics : Infrared and far-infrared lasers
(250.7260) Optoelectronics : Vertical cavity surface emitting lasers

ToC Category:
Optoelectronics

History
Original Manuscript: September 12, 2007
Revised Manuscript: September 26, 2007
Manuscript Accepted: September 26, 2007
Published: September 28, 2007

Citation
Tomi Leinonen, Sanna Ranta, Antti Laakso, Yuri Morozov, Mika Saarinen, and Markus Pessa, "Dual-wavelength generation by vertical external cavity surface-emitting laser," Opt. Express 15, 13451-13456 (2007)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-20-13451


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References

  1. M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. Illegems, E. Gini, H. Melchior, "Continuous wave operation of a mid-infrared semiconductor laser at room temperature," Science 295, 301-305 (2002). [CrossRef] [PubMed]
  2. O. Levi, T.J. Pinguet, T. Skauli, L.A. Eyres, K.R. Parameswaran, J.S. Harris, M.M. Fejer, TJ. Kulp, S.E. Bisson, B. Gerard, E. Lallier, and L. Becouarn, "Difference frequency generation of 8-μm radiation in orientation-patterned GaAs," Opt. Lett. 27, 2091-2093 (2002). [CrossRef]
  3. D. Zheng, l.A. Gordon, Y.S. Wu, R.S. Feigelson, M.M. Fejer, R.L. Byer, and K.L. Vodopyanov, "16-μm infrared generation by difference-frequency mixing in diffusion-bonded-stacked GaAs," Opt. Lett. 23, 1010-1012 (1998). [CrossRef]
  4. U. Simon, S. Waltman, I. Loa, F.K. Tittel, and L. Hollberg, "External-cavity difference-frequency source near 3.2 μm, based on combining a tunable diode laser with a diode-pumped Nd:YAG laser in AgGaS2," J. Opt. Soc. Am. B 12, 323-327 (1995). [CrossRef]
  5. T. Leinonen, Yu. A. Morozov, A. Härkönen, and M. Pessa, "Vertical external-cavity surface-emitting laser for dual-wavelength generation," IEEE Photon. Technol. Lett. 17, 2508-2510 (2005). [CrossRef]
  6. K.R. Poguntke, J.B.D. Soole, A. Scherer, H.P. LeBlanc, C. Caneau, R. Bhat, and M.A. Koza, "Simultaneous multiple wavelength operation of a multistripe array grating integrated cavity laser," Appl. Phys. Lett. 62, 2024-2026 (1993). [CrossRef]
  7. C.L. Wang, Y.H. Chuang, and C.L. Pan, "Two-wavelength interferometer based on a two-color laser diode array and the second-order correlation technique," Opt. Lett. 20, 1071-1073 (1995). [CrossRef] [PubMed]
  8. C.L. Wang, and C.L. Pan, "Tunable multiterahertz beat signal generation from a two-wavelength laser-diode array," Opt. Lett. 20, 1292-1294 (1995). [CrossRef] [PubMed]
  9. C.-C. Huang, C.-H. Cheng, Y.-S. Su, and C.-F. Lin, "174-nm mode spacing in dual-wavelength semiconfuctor laser using nonidentical InGaAsP quantum wells," IEEE Photon. Technol. Lett. 16, 371-373 (2004). [CrossRef]
  10. C.-F. Lin, M.-J. Chen, and B.-L. Lee, "Wide-range tunable dual-wavelength semiconductor laser using asymmetric dual quantum wells," IEEE Photon. Technol. Lett. 10, 1208-1210 (1998). [CrossRef]
  11. P. Pellandini, R. Stanley, R. Houdre, U. Oesterle, and M. Ilegems, "Dual-wavelength laser emission from a coupled semiconductor microcavity," Appl. Phys. Lett. 71, 864-866 (1997). [CrossRef]
  12. P. Michler, M. Hilpert, and G. Reiner, "Dynamics of dual-wavelength emission from a coupled semiconductor microcavity laser," Appl. Phys. Lett. 70, 2073-2075 (1997). [CrossRef]
  13. M. Brunner, K. Gulden, R. Hovel, M. Moser, J.-F. Carlin, R.P. Stanley, and M. Ilegems, "Continuous-wave dual-wavelength lasing in a two-section vertical-cavity laser," IEEE Photon. Technol. Lett. 12, 1316-1318 (2000). [CrossRef]
  14. D.M. Grasso, and K.D. Choquette, "Threshold and modal characteristics of composite-resonator vertical-cavity lasers," IEEE J. Quantum Electron. 39, 1526-1530 (2003). [CrossRef]
  15. V. Badilita, J.-F. Carlin, M. Ilegems, and K. Panajotov, "Rate-equation model for coupled-cavity surface-emitting lasers," IEEE J. Quantum Electron. 40, 1646-1656 (2004). [CrossRef]
  16. Y.A. Morozov, T. Leinonen, A. Härkönen, and M. Pessa, "Simultaneous Dual-Wavelength Emission from Vertical External-Cavity Surface-Emitting Laser: a Numerical Modeling," IEEE J. Quantum Electron. 42, 1055-1061 (2006). [CrossRef]
  17. A. Härkönen, J. Rautiainen, T. Leinonen, Y.A. Morozov, L. Orsila, M. Guina, M. Pessa, and O.G. Okhotnikov, "Intracavity sum-frequency generation in dual-wavelength semiconductor disk laser," IEEE Photon. Technol. Lett. 19, 1550-1552 (2007). [CrossRef]
  18. L. Fan, M. Fallahi, J. Hader, A.R. Zakharian, J.V. Moloney, W. Stolz, S.W. Koch, R. Bedford, and J.T. Murray, "Linearly polarized dual-wavelength vertical-external-cavity surface-emitting laser," Appl. Phys. Lett. 90, 181124 (2007). [CrossRef]
  19. A.C. Tropper, H.D. Foreman, A. Carnache, K.G. Wilcox, and S.H. Hoogland, "Vertical-external-cavity semiconductor lasers," J. Phys. D 37, R75-R85 (2004). [CrossRef]
  20. J.-M. Hopkins, A. J. Maclean, D. Burns, E. Riis, N. Schulz, M. Rattunde, C. Manz, K. Köhler, and J. Wag-ner, "Tunable, Single-frequency, Diode-pumped 2.3µm VECSEL," Opt. Express 15, 8212-8217 (2007). [CrossRef] [PubMed]

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