Generation of Cerenkov radiation at 850 nm in higher-order-mode fiber

doi:10.1364/OE.19.008774

Generation of Cerenkov radiation at 850 nm in higher-order-mode fiber

Ji Cheng, Jennifer H. Lee, Ke Wang, Chris Xu, Kim G. Jespersen, Martin Garmund, Lars Grüner-Nielsen, and Dan Jakobsen »View Author Affiliations

Optics Express, Vol. 19, Issue 9, pp. 8774-8780 (2011)
http://dx.doi.org/10.1364/OE.19.008774

View Full Text Article

Acrobat PDF (1010 KB)

Journal Search
Article Lookup

Article Tools

Citations

Alert me when this article is cited
Export Citation/Save

Article Navigation

▸ Article Outline
– Abstract
1. Introduction
2. Setup
3. Simulated and experimental results
4. Discussion
5. Conclusion
– References and links

Article Tools
Full Text
Article Info
References
Cited By
Figures
Metrics
Download PDF

Viewing Equations in the
HTML Article

Optimal Viewing Recommendations

Full Text
Article Info
References (28)
Cited By
Figures (4)
Metrics

Abstract

We demonstrate generation of Cerenkov radiation at 850 nm in a higher-order-mode (HOM) fiber. The LP₀₂ mode in this solid, silica-based fiber has anomalous dispersion from 690 nm to 810 nm. Cerenkov radiation with 3 nJ pulse energy is generated in this module, exhibiting 60% energy conversion efficiency from the input. The HOM fiber provides a valuable fiber platform for nonlinear wavelength conversion with pulse energies in-between index-guided silica-core photonic crystal fibers and air-core photonic bandgap fibers.

1. Introduction

Soliton self-frequency shift (SSFS) and Cerenkov radiation in optical fibers have been theoretically studied [1

J. P. Gordon, “Theory of the soliton self-frequency shift,” Opt. Lett. 11(10), 662–664 (1986). [CrossRef] [PubMed]

N. Akhmediev and M. Karlsson, “Cherenkov radiation emitted by solitons in optical fibers,” Phys. Rev. A 51(3), 2602–2607 (1995). [CrossRef] [PubMed]

], and experimentally demonstrated in a variety of fibers in the past [3

X. Liu, C. Xu, W. H. Knox, J. K. Chandalia, B. J. Eggleton, S. G. Kosinski, and R. S. Windeler, “Soliton self-frequency shift in a short tapered air-silica microstructure fiber,” Opt. Lett. 26(6), 358–360 (2001). [CrossRef]

–10

N. Ishii, C. Y. Teisset, S. Köhler, E. E. Serebryannikov, T. Fuji, T. Metzger, F. Krausz, A. Baltuska, and A. M. Zheltikov, “Widely tunable soliton frequency shifting of few-cycle laser pulses,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 74(3), 036617 (2006). [CrossRef] [PubMed]

]. It has been shown that a soliton formed in the anomalous dispersion regime can continuously red-shift its central wavelength through the stimulated Raman scattering process. In the case of fibers transitioning to normal dispersion at longer wavelength, SSFS is limited by the second (i.e., at the long wavelength side) zero dispersion wavelength (ZDW). As the frequency-shifted soliton approaches the second ZDW, a phase-matched, red-shifted dispersive wave in the normal dispersion regime, known as Cerenkov radiation, will be emitted by the soliton. The phase-matching condition required for Cerenkov radiation can also be met by the input pulse in the anomalous dispersion regime and a blue-shifted dispersive wave at a wavelength shorter than the first ZDW [9

H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]

,11

K. Moutzouris, E. Adler, F. Sotier, D. Träutlein, and A. Leitenstorfer, “Multimilliwatt ultrashort pulses continuously tunable in the visible from a compact fiber source,” Opt. Lett. 31(8), 1148–1150 (2006). [CrossRef] [PubMed]

,12

A. V. Mitrofanov, Y. M. Linik, R. Buczynski, D. Pysz, D. Lorenc, I. Bugar, A. A. Ivanov, M. V. Alfimov, A. B. Fedotov, and A. M. Zheltikov, “Highly birefringent silicate glass photonic-crystal fiber with polarization-controlled frequency-shifted output: a promising fiber light source for nonlinear Raman microspectroscopy,” Opt. Express 14(22), 10645–10651 (2006). [CrossRef] [PubMed]

]. As photonic crystal fibers (PCFs) can provide anomalous dispersion in different wavelength regimes, both SSFS and Cerenkov radiation have been previously explored in PCFs at various wavelengths [5

N. Nishizawa, Y. Ito, and T. Goto, “0.78-0.90-μm wavelength-tunable femtosecond soliton pulse generation using photonic crystal fiber,” IEEE Photon. Technol. Lett. 14(7), 986–988 (2002). [CrossRef]

D. V. Skryabin, F. Luan, J. C. Knight, and P. S. Russell, “Soliton self-frequency shift cancellation in photonic crystal fibers,” Science 301(5640), 1705–1708 (2003). [CrossRef] [PubMed]

–9

H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]

,12

]. A number of applications have also been demonstrated using these PCF-based wavelength conversion effects [4

H. Lim, J. Buckley, A. Chong, and F. W. Wise, “Fiber-based source of femtosecond pulses tunable from 1.0 to 1.3um,” Electron. Lett. 40(24), 1523 (2004). [CrossRef]

E. R. Andresen, V. Birkedal, J. Thøgersen, and S. R. Keiding, “Tunable light source for coherent anti-Stokes Raman scattering microspectroscopy based on the soliton self-frequency shift,” Opt. Lett. 31(9), 1328–1330 (2006). [CrossRef] [PubMed]

H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]

By propagating light in the LP02 mode, all solid silica-based higher-order-mode (HOM) fibers can be designed to have dispersion characteristics dramatically different from conventional step-index single-mode fibers (SMFs) [13

S. Ramachandran, S. Ghalmi, J. W. Nicholson, M. F. Yan, P. Wisk, E. Monberg, and F. V. Dimarcello, “Anomalous dispersion in a solid, silica-based fiber,” Opt. Lett. 31(17), 2532–2534 (2006). [CrossRef] [PubMed]

,14

K. G. Jespersen, T. Le, L. Grüner-Nielsen, D. Jakobsen, M. E. V. Pederesen, M. B. Smedemand, S. R. Keiding, and B. Palsdottir, “A higher-order-mode fiber delivery for Ti:Sapphire femtosecond lasers,” Opt. Express 18(8), 7798–7806 (2010). [CrossRef] [PubMed]

]. HOM fibers have been engineered to have anomalous dispersion below 1300 nm which was previously possible only with PCFs [15

J. van Howe, J. H. Lee, S. Zhou, F. Wise, C. Xu, S. Ramachandran, S. Ghalmi, and M. F. Yan, “Demonstration of soliton self-frequency shift below 1300 nm in higher-order mode, solid silica-based fiber,” Opt. Lett. 32(4), 340–342 (2007). [CrossRef] [PubMed]

]. This allows HOM fibers to generate SSFS between 1064 nm and 1300 nm [15

,16

J. H. Lee, J. van Howe, C. Xu, and X. Liu, “Soliton self-frequency shift: experimental demonstrations and applications,” IEEE J. Sel. Top. Quantum Electron. 14(3), 713–723 (2008). [CrossRef]

] and red-shifted Cerenkov radiation generation at 1350 nm [17

J. H. Lee, J. van Howe, C. Xu, S. Ramachandran, S. Ghalmi, and M. F. Yan, “Generation of femtosecond pulses at 1350 nm by Cerenkov radiation in higher-order-mode fiber,” Opt. Lett. 32(9), 1053–1055 (2007). [CrossRef] [PubMed]

]. Compared to PCFs, including both index-guided silica-core PCFs and air-core photonic bandgap fibers (PBGFs), HOM fibers are able to generate frequency-shifted solitons and red-shifted Cerenkov radiation at different energy levels [15

]. For index-guided silica-core PCFs, the achievable pulse energy of soliton and Cerenkov radiation is restricted by its high nonlinearity, as silica-core PCFs require a small core size to achieve sufficient anomalous dispersion. Approximating these PCF structures by a silica rod surrounded by air, it has been calculated that the maximum core diameter of PCFs is limited to 2.3 μm to obtain anomalous dispersion below 800 nm [18

J. C. Knight, J. Arriaga, T. A. Birks, A. Ortigosa-Blanch, W. J. Wadsworth, and P. S. J. Russell, “Anomalous dispersion in photonic crystal fiber,” IEEE Photon. Technol. Lett. 12(7), 807–809 (2000). [CrossRef]

,19

M. A. Foster and A. L. Gaeta, “Ultra-low threshold supercontinuum generation in sub-wavelength waveguides,” Opt. Express 12(14), 3137–3143 (2004). [CrossRef] [PubMed]

]. This translates to a core size of 4.15 μm² and an effective mode area (A_eff) of approximately 2 μm². To have the second ZDW at 800 nm for the generation of red-shifted Cerenkov radiation at 850 nm, the maximum core diameter is further limited to less than 800 nm, corresponding to an A_eff of 0.5 μm² [20

M. A. Foster, K. D. Moll, and A. L. Gaeta, “Optimal waveguide dimensions for nonlinear interactions,” Opt. Express 12(13), 2880–2887 (2004). [CrossRef] [PubMed]

]. The core size of an actual silica-core PCF exhibiting the same dispersion characteristics would be even smaller. As a result, the pulse energy obtainable in cleanly frequency-shifted solitons in silica-core PCFs is limited to small fractions of a nanojoule [3

–8

], and the red-shifted Cerenkov radiation in silica–core PCFs demonstrated in previous experiments is below 100 pJ [7

D. V. Skryabin, F. Luan, J. C. Knight, and P. S. Russell, “Soliton self-frequency shift cancellation in photonic crystal fibers,” Science 301(5640), 1705–1708 (2003). [CrossRef] [PubMed]

,21

P. Falk, M. H. Frosz, O. Bang, L. Thrane, P. E. Andersen, A. O. Bjarklev, K. P. Hansen, and J. Broeng, “Broadband light generation around 1300nm through spectrally recoiled solitons and dispersive waves,” Opt. Lett. 33(6), 621–623 (2008). [CrossRef] [PubMed]

]. On the other hand, the pulse energy for solitons in an air-core photonic bandgap fiber (PBGF) is on the order of 100 nJ due to the low nonlinearity of air in the PBGF [22

F. Luan, J. C. Knight, P. S. Russell, S. Campbell, D. Xiao, D. T. Reid, B. J. Mangan, D. P. Williams, and P. J. Roberts, “Femtosecond soliton pulse delivery at 800nm wavelength in hollow-core photonic bandgap fibers,” Opt. Express 12(5), 835–840 (2004). [CrossRef] [PubMed]

]. The nonlinearity values of HOM fibers lie in-between silica-core PCF and air-core PBGF as they propagate light in a solid silica core but with a significantly larger A_eff than that of silica-core PCFs. Thus, the HOM fiber is able to generate soliton and red-shifted Cerenkov radiation with pulse energy on the order of 1 nJ [16

J. H. Lee, J. van Howe, C. Xu, and X. Liu, “Soliton self-frequency shift: experimental demonstrations and applications,” IEEE J. Sel. Top. Quantum Electron. 14(3), 713–723 (2008). [CrossRef]

,17

]. Therefore, the HOM fiber is a valuable platform of nonlinear wavelength conversion with pulse energies in-between index-guided silica-core PCFs and air-core PBGFs.

Nonlinear wavelength conversion at or below 850 nm has also been achieved through blue-shifted Cerenkov radiation at a wavelength shorter than the first ZDW [9

H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]

,12

,23

G. Krauss, D. Fehrenbacher, D. Brida, C. Riek, A. Sell, R. Huber, and A. Leitenstorfer, “All-passive phase locking of a compact Er:fiber laser system,” Opt. Lett. 36(4), 540–542 (2011). [CrossRef] [PubMed]

]. In this case, the required anomalous dispersion regime is shifted to longer wavelengths, reducing the core-size constraints described in the previous paragraph. However, the demonstrated pulse energies in PCFs are still below 100 pJ [9

H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]

,12

]. Similar blue-shifted Cerenkov radiation with approximately 0.4 nJ pulse energy and 5% conversion efficiency has been generated using highly nonlinear germanosilicate bulk fiber [23

]. However, both the pulse energy and the conversion efficiency are significantly lower than red-shifted Cerenkov radiation in HOM fibers. In this paper, we characterize a novel HOM fiber module with a large anomalous dispersion of 120 ps/km/nm and a large A_eff of 15 μm² at 772 nm (approximately 5 times larger than the A_eff of silica-core PCFs designed to have anomalous dispersion below 800 nm). We demonstrate red-shifted Cerenkov radiation generation at 850 nm with 3 nJ pulse energy and up to 60% power conversion efficiency from the input light source (66% photon conversion efficiency) in this module.

2. Setup

The experimental setup is shown in Fig. 1(a) . An 80 MHz mode-locked Ti:Sapphire laser is used as the input source. The initial pulse launched into the HOM fiber module is centered at 772 nm and has a spectral bandwidth (full width at half maximum, FWHM) of 8 nm. The HOM fiber module consists of a 1.3 m SMF (ClearLite 780-11, OFS), a long period grating (LPG) to convert light from the fundamental mode (LP₀₁) to the LP₀₂ mode with more than 99% efficiency between 762 nm and 778 nm, and 5.3 m HOM fiber (FemtoComp 800, OFS). The LP₀₂ mode of the HOM fiber has anomalous dispersion between 690 nm and 810 nm [Fig. 1(b)]. The A_eff of the LP₀₂ mode is between 10 and 15 μm² [Fig. 1(c)] in the vicinity of the input wavelength. The input power to the HOM fiber module can be tuned without changing the input polarization by a variable optical attenuator (VOA), which consists of a half-wave-plate and a polarizer. The input pulse is broadened to 300 fs by dispersion in the optical isolator. It is then further broadened to 2 ps by a glass rod to reduce the effects of spectral broadening from self-phase modulation in the SMF pigtail and to protect the LPG from nonlinear photodamage. The output pulse is characterized with an optical spectrum analyzer after collimation. A long pass filter with a cutoff wavelength at 810 nm is used to separate the Cerenkov radiation from the residue input. The pulse energy of the Cerenkov radiation is measured, taking into account the transmission of the long pass filter. The filtered Cerenkov radiation is temporally characterized by a second-order autocorrelator.

Fig. 1 (a) Experimental setup, (b) Calculated dispersion of the LP₀₂ mode of the HOM fiber, (c) Calculated A_eff of the LP₀₂ mode of the HOM fiber.

3. Simulated and experimental results

The fiber propagation process is numerically modeled using the generalized nonlinear Schrödinger equation [24

J. Laegsgaard, “Mode profile dispersion in the generalised nonlinear Schrödinger equation,” Opt. Express 15(24), 16110–16123 (2007). [CrossRef] [PubMed]

,25

J. M. Dudley and J. R. Taylor, “Nonlinear fibre optics overview,” in Supercontinuum Generation in Optical Fibers (Cambridge University Press, 2010), Chapter 3, 33–51.

]. The laser source is modeled as a hyperbolic secant pulse with 90 fs FWHM. The pulse is broadened to 2 ps by normal dispersion before entering the HOM fiber module. For propagation in the HOM fiber, our simulation incorporates the contribution of dispersion, self-phase modulation, stimulated Raman scattering, self-steepening, wavelength dependent A_eff, and other high order nonlinear effects. The nonlinear refractive index used in the simulation is n₂ = 2.0 × 10⁻²⁰ m²/W. The dispersion coefficients (up to 14th order) and A_eff values are obtained by directly fitting the dispersion and A_eff curves shown in Figs. 1(b) and 1(c). The Raman response function is written as

R (t) = (1 - f_{R}) δ (t) + f_{R} \frac{τ_{1}^{2} + τ_{2}^{2}}{τ_{1} τ_{2}^{2}} \exp (- \frac{t}{τ_{2}}) \sin (\frac{t}{τ_{1}}) Θ (t),

(1)

where f_R = 0.18 is the fractional contribution of the delayed Raman response, τ₁ = 12.2 fs, τ₂ = 32 fs, Θ(t) is the Heaviside step function, and δ(t) is the Dirac delta function [25

J. M. Dudley and J. R. Taylor, “Nonlinear fibre optics overview,” in Supercontinuum Generation in Optical Fibers (Cambridge University Press, 2010), Chapter 3, 33–51.

We systematically characterize the output spectra at different input pulse energies (from 0.15 nJ to 5 nJ) to show the effects of nonlinear pulse propagation. Spectra measured at 0.2 nm resolution with different input pulse energies are shown in Fig. 2(a) . At 0.15 nJ input pulse energy (Fig. 2), a 777 nm frequency-shifted soliton is observed with a pulse energy greater than 0.1 nJ. At higher input pulse energies, the soliton can be further red-shifted, and its wavelength is eventually “locked” at 795 nm at 0.3 nJ input pulse energy (Fig. 2), due to the balance of SSFS and the spectral recoil from the generation of the Cerenkov radiation. Multiple solitons with spectral overlap are generated at higher input energies. The spectral beating produced by multiple solitons is clearly observable in the spectrum taken at 0.42 nJ input pulse energy (Fig. 2). The measured Cerenkov pulse energy as a function of input pulse energy is shown in Fig. 3 . The onset of Cerenkov radiation occurs at approximately 0.22 nJ input pulse energy. A threshold behavior (between input energies of 0.22 nJ and 0.25 nJ) and a plateau behavior (between input energies of 0.25 nJ and 0.4 nJ) are observed at the initial stage of the generation of the Cerenkov radiation, which are consistent with previous observations in PCFs and HOM fibers at other wavelengths [7

D. V. Skryabin, F. Luan, J. C. Knight, and P. S. Russell, “Soliton self-frequency shift cancellation in photonic crystal fibers,” Science 301(5640), 1705–1708 (2003). [CrossRef] [PubMed]

,17

]. The Cerenkov energy rapidly increases again at 0.4 nJ, indicating the onset of the Cerenkov radiation generated by the second frequency-shifted soliton. These behaviors are all identified in Fig. 3.

Fig. 2 (a) Measured spectra at various pulse energies showing soliton generation, soliton self-frequency shift, and Cerenkov radiation. (b) Simulated spectra with the same input conditions. All traces are taken at 0.2 nm spectral resolution. The soliton and Cerenkov radiation are marked by arrows. The input wavelength and the zero-dispersion wavelength (ZDW) are denoted by dashed lines and the input pulse energy (E) is indicated on each trace.

Fig. 3 (a) Experimentally measured (solid) and calculated (dashed) Cerenkov pulse energy as a function of input pulse energy. Inset: Experimental results compared with simulated Cerenkov pulse energy at input pulse energies below 0.8 nJ.

To compare with the experimental data, Fig. 2(b) and the dashed line in Fig. 3 show the simulated traces generated using our numerical modeling program. Simulation results are able to match the spectral features and the pulse energies of Cerenkov radiation at input energies from 0.15 nJ to 1 nJ. The simulated spectra at high input energies show many pronounced fine substructures which are extremely sensitive to small changes of the input energy. These fine spectral features were not observed in our experiments. We believe this discrepancy is due in part to the fact that the measured spectra are averaged over many laser pulses at slightly different pulse energies. Similar phenomenon was also theoretically predicted and experimentally observed in previous works on supercontinuum generation [26

A. L. Gaeta, “Nonlinear propagation and continuum generation in microstructured optical fibers,” Opt. Lett. 27(11), 924–926 (2002). [CrossRef]

]. Other discrepancies between the simulated and experimental results are potentially caused by the inaccuracy of the calculated dispersion and A_eff curves. Note that at high input energies, simulation also shows 5-10% higher conversion efficiency of the Cerenkov radiation and lower levels of the residue input than the experimental results. This difference might be attributed to the omission of the vectorial nature of the pulse propagation in the HOM fiber in simulation.

At 5 nJ input pulse energy, Cerenkov radiation with 3 nJ pulse energy and 50 nm spectral bandwidth, which translates to a spectral density of 4.8 mW/nm at 80 MHz repetition rate, can be generated without exhibiting super-continuum-like spectral features. The measured and simulated second-order intensity autocorrelation trace of the Cerenkov radiation at 5 nJ input pulse energy is shown in Fig. 4 . The measured and simulated traces show FWHM values of 10 ps and 12 ps, respectively. The long pulse duration of the Cerenkov radiation is due to the long propagation distance (6 m), the broad spectral bandwidth (50 nm), and the high dispersion value of the HOM fiber (100 ps/nm/km). While the Cerenkov energy and its power spectral density can be further increased by using a more energetic input, the potential photo-degradation of the LPGs in the HOM fiber modules prevents us from experimenting at higher input powers.

Fig. 4 Measured (a) and simulated (b) second-order intensity autocorrelation trace of the Cerenkov radiation at 5 nJ input pulse energy.

4. Discussion

Blue-shifted Cerenkov radiation at comparable wavelengths can be generated using the first ZDW of the waveguide. This approach does not require the fiber to achieve anomalous dispersion below 850 nm, and thus the core diameter of the waveguide can exceed 2.3 μm. However, high energy input pulse must be launched at a wavelength much longer than the first ZDW to avoid super-continuum generation, which significantly limits the energy conversion efficiency [9

H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]

]. More importantly, red-shifted Cerenkov radiation has much higher energy conversion efficiency than blue-shifted Cerenkov radiation because stimulated Raman scattering shifts the pulse towards the longer wavelength and facilitates the energy conversion to the Cerenkov radiation. For example, the results reported by G. Krauss et al. for the blue-shifted Cerenkov radiation at 860 nm have approximately 0.4 nJ pulse energy with an 8 nJ femtosecond input [23

]. The red-shifted Cerenkov radiation reported in our paper has approximately 3 nJ pulse energy with a 5 nJ input. Both the conversion efficiency and the absolute pulse energy represent approximately an order of magnitude improvement over the existing results. These improvements are enabled by the unique propagation characteristics of the HOM fiber, which allows us to generate red-shifted Cerenkov radiation in a fiber with a relatively large A_eff.

The demonstrated pulse energy and power spectral density of the red-shifted Cerenkov radiation in the HOM fiber is also significantly higher than red-shifted Cerenkov radiation obtainable in PCFs at comparable wavelengths. Because the much smaller A_eff of the silica-core PCFs (less than 800 nm core diameter for generating the red-shifted Cerenkov radiation at 850 nm) results in much higher optical nonlinearity, supercontinuum could be generated by femtosecond input pulses with 1 nJ pulse energy, which results in much lower power spectral density of the Cerenkov radiation. High power spectral density can potentially be achieved in silica-core PCFs with high power continuous-wave input, but the lack of temporal confinement makes the output unsuitable for various applications that require short pulses, such as pump-probe spectroscopy and Coherent Raman Scattering microscopy.

The picosecond Cerenkov radiation generated in the HOM fiber, together with the residue pump light, provides a convenient, synchronized 2-color picosecond source with high pulse energies, which is desirable for a variety of practical applications including pump-probe spectroscopy, modulation transfer microscopy [27

C. W. Freudiger, W. Min, B. G. Saar, S. Lu, G. R. Holtom, C. He, J. C. Tsai, J. X. Kang, and X. S. Xie, “Label-free biomedical imaging with high sensitivity by stimulated Raman scattering microscopy,” Science 322(5909), 1857–1861 (2008). [CrossRef] [PubMed]

], stimulated emission depletion microscopy (STED) [28

T. A. Klar, S. Jakobs, M. Dyba, A. Egner, and S. W. Hell, “Fluorescence microscopy with diffraction resolution barrier broken by stimulated emission,” Proc. Natl. Acad. Sci. U.S.A. 97(15), 8206–8210 (2000). [CrossRef] [PubMed]

], etc. The HOM fiber can also be readily integrated with a frequency-doubled femtosecond fiber laser at 775 nm to achieve a fiber-based, picosecond, two-color light source. Although red-shifted CR in an HOM fiber at 1350 nm has been reported in the past, and it is well-known in theory that the wavelength of the CR can be engineered by shifting the dispersion curve, it is challenging to shift the dispersion curve to much shorter wavelengths due to the large increase of the material dispersion. Our results demonstrate that the concept of CR in an HOM fiber can be applied to achieve nonlinear frequency conversion at much shorter wavelengths while maintaining its significant advantages in higher pulse energy and conversion efficiency.

5. Conclusion

In summary, we demonstrate SSFS below 800 nm and Cerenkov generation at 850 nm in a solid silica-based HOM fiber module. The HOM module generates significantly more energetic Cerenkov radiation than index-guided silica-core PCFs at comparable wavelengths. We are able to achieve a 3 nJ Cerenkov radiation pulse energy, with high power conversion efficiency of 60% and approximately 4.8 mW/nm spectral density. The HOM fiber module provides a valuable fiber platform for nonlinear wavelength conversion around 800 nm with pulse energies in-between index-guided silica-core photonic crystal fibers and air-core photonic bandgap fibers. This fiber platform can also be tailored to other wavelengths of interest with proper dispersion engineering.

Acknowledgments

This work is supported by NIH/NCRR, grant R21RR024415. The authors thank Frank Wise and Watt W. Webb for sharing equipment, and John M Dudley for valuable discussions.

References and links

1.	J. P. Gordon, “Theory of the soliton self-frequency shift,” Opt. Lett. 11(10), 662–664 (1986). [CrossRef] [PubMed]
2.	N. Akhmediev and M. Karlsson, “Cherenkov radiation emitted by solitons in optical fibers,” Phys. Rev. A 51(3), 2602–2607 (1995). [CrossRef] [PubMed]
3.	X. Liu, C. Xu, W. H. Knox, J. K. Chandalia, B. J. Eggleton, S. G. Kosinski, and R. S. Windeler, “Soliton self-frequency shift in a short tapered air-silica microstructure fiber,” Opt. Lett. 26(6), 358–360 (2001). [CrossRef]
4.	H. Lim, J. Buckley, A. Chong, and F. W. Wise, “Fiber-based source of femtosecond pulses tunable from 1.0 to 1.3um,” Electron. Lett. 40(24), 1523 (2004). [CrossRef]
5.	N. Nishizawa, Y. Ito, and T. Goto, “0.78-0.90-μm wavelength-tunable femtosecond soliton pulse generation using photonic crystal fiber,” IEEE Photon. Technol. Lett. 14(7), 986–988 (2002). [CrossRef]
6.	I. Cristiani, R. Tediosi, L. Tartara, and V. Degiorgio, “Dispersive wave generation by solitons in microstructured optical fibers,” Opt. Express 12(1), 124–135 (2004). [CrossRef] [PubMed]
7.	D. V. Skryabin, F. Luan, J. C. Knight, and P. S. Russell, “Soliton self-frequency shift cancellation in photonic crystal fibers,” Science 301(5640), 1705–1708 (2003). [CrossRef] [PubMed]
8.	E. R. Andresen, V. Birkedal, J. Thøgersen, and S. R. Keiding, “Tunable light source for coherent anti-Stokes Raman scattering microspectroscopy based on the soliton self-frequency shift,” Opt. Lett. 31(9), 1328–1330 (2006). [CrossRef] [PubMed]
9.	H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]
10.	N. Ishii, C. Y. Teisset, S. Köhler, E. E. Serebryannikov, T. Fuji, T. Metzger, F. Krausz, A. Baltuska, and A. M. Zheltikov, “Widely tunable soliton frequency shifting of few-cycle laser pulses,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 74(3), 036617 (2006). [CrossRef] [PubMed]
11.	K. Moutzouris, E. Adler, F. Sotier, D. Träutlein, and A. Leitenstorfer, “Multimilliwatt ultrashort pulses continuously tunable in the visible from a compact fiber source,” Opt. Lett. 31(8), 1148–1150 (2006). [CrossRef] [PubMed]
12.	A. V. Mitrofanov, Y. M. Linik, R. Buczynski, D. Pysz, D. Lorenc, I. Bugar, A. A. Ivanov, M. V. Alfimov, A. B. Fedotov, and A. M. Zheltikov, “Highly birefringent silicate glass photonic-crystal fiber with polarization-controlled frequency-shifted output: a promising fiber light source for nonlinear Raman microspectroscopy,” Opt. Express 14(22), 10645–10651 (2006). [CrossRef] [PubMed]
13.	S. Ramachandran, S. Ghalmi, J. W. Nicholson, M. F. Yan, P. Wisk, E. Monberg, and F. V. Dimarcello, “Anomalous dispersion in a solid, silica-based fiber,” Opt. Lett. 31(17), 2532–2534 (2006). [CrossRef] [PubMed]
14.	K. G. Jespersen, T. Le, L. Grüner-Nielsen, D. Jakobsen, M. E. V. Pederesen, M. B. Smedemand, S. R. Keiding, and B. Palsdottir, “A higher-order-mode fiber delivery for Ti:Sapphire femtosecond lasers,” Opt. Express 18(8), 7798–7806 (2010). [CrossRef] [PubMed]
15.	J. van Howe, J. H. Lee, S. Zhou, F. Wise, C. Xu, S. Ramachandran, S. Ghalmi, and M. F. Yan, “Demonstration of soliton self-frequency shift below 1300 nm in higher-order mode, solid silica-based fiber,” Opt. Lett. 32(4), 340–342 (2007). [CrossRef] [PubMed]
16.	J. H. Lee, J. van Howe, C. Xu, and X. Liu, “Soliton self-frequency shift: experimental demonstrations and applications,” IEEE J. Sel. Top. Quantum Electron. 14(3), 713–723 (2008). [CrossRef]
17.	J. H. Lee, J. van Howe, C. Xu, S. Ramachandran, S. Ghalmi, and M. F. Yan, “Generation of femtosecond pulses at 1350 nm by Cerenkov radiation in higher-order-mode fiber,” Opt. Lett. 32(9), 1053–1055 (2007). [CrossRef] [PubMed]
18.	J. C. Knight, J. Arriaga, T. A. Birks, A. Ortigosa-Blanch, W. J. Wadsworth, and P. S. J. Russell, “Anomalous dispersion in photonic crystal fiber,” IEEE Photon. Technol. Lett. 12(7), 807–809 (2000). [CrossRef]
19.	M. A. Foster and A. L. Gaeta, “Ultra-low threshold supercontinuum generation in sub-wavelength waveguides,” Opt. Express 12(14), 3137–3143 (2004). [CrossRef] [PubMed]
20.	M. A. Foster, K. D. Moll, and A. L. Gaeta, “Optimal waveguide dimensions for nonlinear interactions,” Opt. Express 12(13), 2880–2887 (2004). [CrossRef] [PubMed]
21.	P. Falk, M. H. Frosz, O. Bang, L. Thrane, P. E. Andersen, A. O. Bjarklev, K. P. Hansen, and J. Broeng, “Broadband light generation around 1300nm through spectrally recoiled solitons and dispersive waves,” Opt. Lett. 33(6), 621–623 (2008). [CrossRef] [PubMed]
22.	F. Luan, J. C. Knight, P. S. Russell, S. Campbell, D. Xiao, D. T. Reid, B. J. Mangan, D. P. Williams, and P. J. Roberts, “Femtosecond soliton pulse delivery at 800nm wavelength in hollow-core photonic bandgap fibers,” Opt. Express 12(5), 835–840 (2004). [CrossRef] [PubMed]
23.	G. Krauss, D. Fehrenbacher, D. Brida, C. Riek, A. Sell, R. Huber, and A. Leitenstorfer, “All-passive phase locking of a compact Er:fiber laser system,” Opt. Lett. 36(4), 540–542 (2011). [CrossRef] [PubMed]
24.	J. Laegsgaard, “Mode profile dispersion in the generalised nonlinear Schrödinger equation,” Opt. Express 15(24), 16110–16123 (2007). [CrossRef] [PubMed]
25.	J. M. Dudley and J. R. Taylor, “Nonlinear fibre optics overview,” in Supercontinuum Generation in Optical Fibers (Cambridge University Press, 2010), Chapter 3, 33–51.
26.	A. L. Gaeta, “Nonlinear propagation and continuum generation in microstructured optical fibers,” Opt. Lett. 27(11), 924–926 (2002). [CrossRef]
27.	C. W. Freudiger, W. Min, B. G. Saar, S. Lu, G. R. Holtom, C. He, J. C. Tsai, J. X. Kang, and X. S. Xie, “Label-free biomedical imaging with high sensitivity by stimulated Raman scattering microscopy,” Science 322(5909), 1857–1861 (2008). [CrossRef] [PubMed]
28.	T. A. Klar, S. Jakobs, M. Dyba, A. Egner, and S. W. Hell, “Fluorescence microscopy with diffraction resolution barrier broken by stimulated emission,” Proc. Natl. Acad. Sci. U.S.A. 97(15), 8206–8210 (2000). [CrossRef] [PubMed]

OCIS Codes
(060.2380) Fiber optics and optical communications : Fiber optics sources and detectors
(190.4370) Nonlinear optics : Nonlinear optics, fibers

ToC Category:
Nonlinear Optics

History
Original Manuscript: February 18, 2011
Revised Manuscript: March 28, 2011
Manuscript Accepted: March 29, 2011
Published: April 20, 2011

Citation
Ji Cheng, Jennifer H. Lee, Ke Wang, Chris Xu, Kim G. Jespersen, Martin Garmund, Lars Grüner-Nielsen, and Dan Jakobsen, "Generation of Cerenkov radiation at 850 nm in higher-order-mode fiber," Opt. Express 19, 8774-8780 (2011)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-19-9-8774

Sort: Author | Year | Journal | Reset

References

J. P. Gordon, “Theory of the soliton self-frequency shift,” Opt. Lett. 11(10), 662–664 (1986). [CrossRef] [PubMed]
N. Akhmediev and M. Karlsson, “Cherenkov radiation emitted by solitons in optical fibers,” Phys. Rev. A 51(3), 2602–2607 (1995). [CrossRef] [PubMed]
X. Liu, C. Xu, W. H. Knox, J. K. Chandalia, B. J. Eggleton, S. G. Kosinski, and R. S. Windeler, “Soliton self-frequency shift in a short tapered air-silica microstructure fiber,” Opt. Lett. 26(6), 358–360 (2001). [CrossRef]
H. Lim, J. Buckley, A. Chong, and F. W. Wise, “Fiber-based source of femtosecond pulses tunable from 1.0 to 1.3um,” Electron. Lett. 40(24), 1523 (2004). [CrossRef]
N. Nishizawa, Y. Ito, and T. Goto, “0.78-0.90-μm wavelength-tunable femtosecond soliton pulse generation using photonic crystal fiber,” IEEE Photon. Technol. Lett. 14(7), 986–988 (2002). [CrossRef]
I. Cristiani, R. Tediosi, L. Tartara, and V. Degiorgio, “Dispersive wave generation by solitons in microstructured optical fibers,” Opt. Express 12(1), 124–135 (2004). [CrossRef] [PubMed]
D. V. Skryabin, F. Luan, J. C. Knight, and P. S. Russell, “Soliton self-frequency shift cancellation in photonic crystal fibers,” Science 301(5640), 1705–1708 (2003). [CrossRef] [PubMed]
E. R. Andresen, V. Birkedal, J. Thøgersen, and S. R. Keiding, “Tunable light source for coherent anti-Stokes Raman scattering microspectroscopy based on the soliton self-frequency shift,” Opt. Lett. 31(9), 1328–1330 (2006). [CrossRef] [PubMed]
H. Tu and S. A. Boppart, “Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation,” Opt. Express 17(12), 9858–9872 (2009). [CrossRef] [PubMed]
N. Ishii, C. Y. Teisset, S. Köhler, E. E. Serebryannikov, T. Fuji, T. Metzger, F. Krausz, A. Baltuska, and A. M. Zheltikov, “Widely tunable soliton frequency shifting of few-cycle laser pulses,” Phys. Rev. E Stat. Nonlin. Soft Matter Phys. 74(3), 036617 (2006). [CrossRef] [PubMed]
K. Moutzouris, E. Adler, F. Sotier, D. Träutlein, and A. Leitenstorfer, “Multimilliwatt ultrashort pulses continuously tunable in the visible from a compact fiber source,” Opt. Lett. 31(8), 1148–1150 (2006). [CrossRef] [PubMed]
A. V. Mitrofanov, Y. M. Linik, R. Buczynski, D. Pysz, D. Lorenc, I. Bugar, A. A. Ivanov, M. V. Alfimov, A. B. Fedotov, and A. M. Zheltikov, “Highly birefringent silicate glass photonic-crystal fiber with polarization-controlled frequency-shifted output: a promising fiber light source for nonlinear Raman microspectroscopy,” Opt. Express 14(22), 10645–10651 (2006). [CrossRef] [PubMed]
S. Ramachandran, S. Ghalmi, J. W. Nicholson, M. F. Yan, P. Wisk, E. Monberg, and F. V. Dimarcello, “Anomalous dispersion in a solid, silica-based fiber,” Opt. Lett. 31(17), 2532–2534 (2006). [CrossRef] [PubMed]
K. G. Jespersen, T. Le, L. Grüner-Nielsen, D. Jakobsen, M. E. V. Pederesen, M. B. Smedemand, S. R. Keiding, and B. Palsdottir, “A higher-order-mode fiber delivery for Ti:Sapphire femtosecond lasers,” Opt. Express 18(8), 7798–7806 (2010). [CrossRef] [PubMed]
J. van Howe, J. H. Lee, S. Zhou, F. Wise, C. Xu, S. Ramachandran, S. Ghalmi, and M. F. Yan, “Demonstration of soliton self-frequency shift below 1300 nm in higher-order mode, solid silica-based fiber,” Opt. Lett. 32(4), 340–342 (2007). [CrossRef] [PubMed]
J. H. Lee, J. van Howe, C. Xu, and X. Liu, “Soliton self-frequency shift: experimental demonstrations and applications,” IEEE J. Sel. Top. Quantum Electron. 14(3), 713–723 (2008). [CrossRef]
J. H. Lee, J. van Howe, C. Xu, S. Ramachandran, S. Ghalmi, and M. F. Yan, “Generation of femtosecond pulses at 1350 nm by Cerenkov radiation in higher-order-mode fiber,” Opt. Lett. 32(9), 1053–1055 (2007). [CrossRef] [PubMed]
J. C. Knight, J. Arriaga, T. A. Birks, A. Ortigosa-Blanch, W. J. Wadsworth, and P. S. J. Russell, “Anomalous dispersion in photonic crystal fiber,” IEEE Photon. Technol. Lett. 12(7), 807–809 (2000). [CrossRef]
M. A. Foster and A. L. Gaeta, “Ultra-low threshold supercontinuum generation in sub-wavelength waveguides,” Opt. Express 12(14), 3137–3143 (2004). [CrossRef] [PubMed]
M. A. Foster, K. D. Moll, and A. L. Gaeta, “Optimal waveguide dimensions for nonlinear interactions,” Opt. Express 12(13), 2880–2887 (2004). [CrossRef] [PubMed]
P. Falk, M. H. Frosz, O. Bang, L. Thrane, P. E. Andersen, A. O. Bjarklev, K. P. Hansen, and J. Broeng, “Broadband light generation around 1300nm through spectrally recoiled solitons and dispersive waves,” Opt. Lett. 33(6), 621–623 (2008). [CrossRef] [PubMed]
F. Luan, J. C. Knight, P. S. Russell, S. Campbell, D. Xiao, D. T. Reid, B. J. Mangan, D. P. Williams, and P. J. Roberts, “Femtosecond soliton pulse delivery at 800nm wavelength in hollow-core photonic bandgap fibers,” Opt. Express 12(5), 835–840 (2004). [CrossRef] [PubMed]
G. Krauss, D. Fehrenbacher, D. Brida, C. Riek, A. Sell, R. Huber, and A. Leitenstorfer, “All-passive phase locking of a compact Er:fiber laser system,” Opt. Lett. 36(4), 540–542 (2011). [CrossRef] [PubMed]
J. Laegsgaard, “Mode profile dispersion in the generalised nonlinear Schrödinger equation,” Opt. Express 15(24), 16110–16123 (2007). [CrossRef] [PubMed]
J. M. Dudley and J. R. Taylor, “Nonlinear fibre optics overview,” in Supercontinuum Generation in Optical Fibers (Cambridge University Press, 2010), Chapter 3, 33–51.
A. L. Gaeta, “Nonlinear propagation and continuum generation in microstructured optical fibers,” Opt. Lett. 27(11), 924–926 (2002). [CrossRef]
C. W. Freudiger, W. Min, B. G. Saar, S. Lu, G. R. Holtom, C. He, J. C. Tsai, J. X. Kang, and X. S. Xie, “Label-free biomedical imaging with high sensitivity by stimulated Raman scattering microscopy,” Science 322(5909), 1857–1861 (2008). [CrossRef] [PubMed]
T. A. Klar, S. Jakobs, M. Dyba, A. Egner, and S. W. Hell, “Fluorescence microscopy with diffraction resolution barrier broken by stimulated emission,” Proc. Natl. Acad. Sci. U.S.A. 97(15), 8206–8210 (2000). [CrossRef] [PubMed]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Click here to see a list of articles that cite this paper