Research Results 17

2019

Femtosecond writing of fiber Bragg gratings in multicore fibers for sensor and laser applications

A method has been developed for writing uniform and non-uniform fiber Bragg gratings (FBG) in selected cores of multicore fibers (MCF) using femtosecond (fs) laser radiation. Based on the FBG array in 7-core MCF, a sensor was fabricated, allowing for reconstruction a three-dimensional shape of the optical fiber with high accuracy (Fig. 1). Based on the 2-core fiber with cross-coupling between the cores, new schemes of fiber Raman lasers were implemented. It was shown that in a resonator with FBG written in one of the cores, a significant narrowing of the lasing line occurs, as compared to a broadband ring mirror. In a resonator with a pair of FBGs written in different cores, multiwave lasing was obtained.

Безымянный

Fig.1: The scheme for measuring the shape of the MCF using an FBG array (a) and the result of reconstructing different shapes of the MCF (b).

Published works:

[1] S. S. Yakushin et al, “A study of bending effect on the femtosecond-pulse inscribed fiber Bragg gratings in a dual-core fiber,” Optical Fiber Technology, vol. 43, pp. 101–105, 2018.

[2] A. A. Wolf, A. V. Dostovalov, S. Wabnitz, and S. A. Babin, “Femtosecond writing of refractive index structures in multimode and multicore fibres,” Quantum Electronics, vol. 48, no. 12, pp. 1128–1131, 2018.

[3] M. I. Skvortsov et al, “Narrowband Raman fibre laser based on a dual-core optical fibre with FBGs inscribed by femtosecond radiation,” Quantum Electronics, vol. 48, no. 12, pp. 1089–1094, 2018.

[4] A. Wolf et al, “Femtosecond point-by-point inscription of 3D FBG arrays in 7-core fibers with straight and twisted cores,” in Proc. of SPIE Vol. 11199, Seventh European Workshop on Optical Fibre Sensors, vol. 11199, p. 1119934, 2019.

[5] A. Wolf, A. Dostovalov, K. Bronnikov, and S. Babin, “Arrays of fiber Bragg gratings selectively inscribed in different cores of 7-core spun optical fiber by IR femtosecond laser pulses,” Optics Express, vol. 27, no. 10, p. 13978, 2019.

[6] A. Wolf, A. Dostovalov, K. Bronnikov, and S. Babin, “Direct core-selective inscription of Bragg grating structures in seven-core optical fibers by femtosecond laser pulses,” in Proc. SPIE 11029, Micro- structured and Specialty Optical Fibres VI, p. 110290E, 2019.

[7] M. I. Skvortsov et al, “Random Raman fiber laser based on a twin-core fiber with FBGs inscribed by femtosecond radiation,” Optics Letters, vol. 44, no. 2, pp. 295–298, 2019.

[8] A. A. Wolf et al, “Fabrication of uniform and non-uniform FBGs in 7-core optical fiber using femtosecond point-by-point inscription technique,” Applied Photonics, vol. 6, no. 1–2, pp. 48–56, 2019 (in Russian).

[9] K. Bronnikov et al, “Durable shape sensor based on FBG array inscribed in polyimide-coated 7-core optical fiber”, submitted to Optics Express, vol. 26, no. 27, 2019.

2016

Fiber Bragg gratings writing by a femtosecond laser radiation for laser and sensors applications

The technology of direct point-by-point fiber Bragg gratings (FBG) writing by a femtosecond laser IR radiation has been developed, which offers an opportunity to inscribe FBGs through a plastic protective coating of photosensitive and non-photosensitive fibers. The inscribed FBGs are characterized by a high mechanical strength and temperature resistance of the induced refractive index modulation. The experimental spectra agree well with the calculated ones thus confirming a high accuracy of the proposed writing technology. The FBG length is varied from 0.1 to 10 cm. The narrowband FBG of 16.5 pm width have been demonstrated. The inscribed FBGs are successfully used in fiber laser and sensor systems, particularly, as temperature and strain sensors in smart composite materials.

References:

1. A.V. Dostovalov, A.A. Wolf, A.V. Parygin, V.E. Zuybin and S.A. Babin  "Femtosecond point-by-point inscription of Bragg gratings by drawing a coated fiber through ferrule," Opt. Express, vol. 24, no. 14, pp. 16232–16237 (2016).

2. A.V. Dostovalov, A.A. Wolf, V.K. Mezentsev, A.G. Okhrimchuk, and S.A. Babin "Quantitative characterization of energy absorption in femtosecond laser micro-modification of fused silica," Opt. Express, vol. 23, no. 25, p. 32541 (2015).

3. V. V. Shishkin, V. S. Terentyev, D. S. Kharenko, A. V. Dostovalov, A. A. Wolf, V. A. Simonov, M. Y. Fedotov, A. M. Shienok, I. S. Shelemba, and S. A. Babin, “Separate temperature and strain measurements in polymer composite material by embedded fiber-optic sensors based on FBGs with increased sensitivity difference,” J. Sensors, vol. 2016, article 3230968 (2016).

 

Singlemode Raman lasing in a multimode graded-index fiber with direct diode pumping

Generation of fiber Raman laser with direct diode pumping has been obtained for the first time in the spectral range of <1 micron, where conventional fiber lasers practically do not work. It has been shown that the Raman conversion in a cavity formed in graded-index fiber by special fiber Bragg gratings (FBGs), is accompanied by the beam quality improvement from Мp2~20 (multimode pump radiation at 915 nm) to Мs2~1,2 (singlemode generation at 954 nm). The main contribution to the effect is provided by the weak (R~4%) output FBG, which is formed by femtosecond laser selectively in the central part of the graded-index fiber core. The slope efficiency reaches ~40% at the output power level of >10 W. The opportunite to operate without output mirror (using Rayleigh scattering distributed feedback instead) has been also demonstrated. The obtained levels of power and beam quality enable efiicient frequency doubling of the generated radiation. Thus, new type of fiber lasers operating in near-IR and visible range has been proposed and realized, which is interesting for biomedical diagnoctics, laser dysplays and other applications.

References:

1. S.I Kablukov, E.I. Dontsova, E.A. Zlobina, I.N. Nemov, A.A. Vlasov, and S.A. Babin, “An LD-pumped Raman fiber laser operating below 1 μm,” Laser Phys. Lett. 10, 085103 (2013).2.

2. S.A. Babin, E.I. Dontsova, and S.I. Kablukov. “Random fiber laser directly pumped by a high-power laser diode,” Opt. Lett. 38, 17, 3301-3303 (2013).

 

3. E.A. Zlobina, S.I. Kablukov, M.I. Skvortsov, I.N. Nemov, and S.A. Babin, “954 nm Raman fiber laser with multimode laser diode pumping,” Laser Phys. Lett. 13, 035102 (2016).

 

 

 

2015

Self-sweeping single-frequency fiber laser

A fiber laser with frequency tuning based on new physical principles is demonstrated. A formation in active medium of dynamic spatial gain and refractive index gratings by a standing wave field leads to the generation of sequence of pulses, which equally spaced in time and frequency domain. Each pulse has a spectral width of less than 1 MHz and has the same phase as previous one. The possibility of practical applications of the source for interrogation of fiber sensors based on Bragg gratings and for short pulse synthesis by coherent combining of the sequence is proved. The simplicity and robustness are additional benefits of the laser.

Publications

  • Lobach I.A. et al., “Self-scanned single-frequency operation of a fiber laser driven by a self-induced phase grating”, Laser Phys. Lett., 11, No. 4, 045103 (2014).
  • Lobach I.A. et al., “Single-frequency Bismuth-doped fiber laser with quasi-continuous self-sweeping”, Opt. Express, 23, 24833-24842 (2015).
  • Lobach I.A. et al., “Fourier synthesis with single-mode pulses from a multimode laser”, Opt. Lett., 40, 3671-3674 (2015).
  • Lobach I.A., Kablukov S.I., “Application of a self-sweeping Yb-doped fiber laser for high-resolution characterization of phase-shifted FBGs”, J. Lightwave Technol., 31, No. 18, 2982-2987 (2013).

Nonlinear kinetics of fiber lasers with random distributed feedback

Nonlinear kinetics of wave turbulence in open cyclic systems is developed, in which correlation functions of the wave fields change sufficiently within each cycle. The model has been applied for the description of generation spectra in Raman fiber lasers with random distributed feedback. The obtained solution converges with the Shawlow-Towns’ linear kinetics and describes the experiment. The proposed approach can be used for the description of wave turbulence behavior in multimode lasers, long fiber optic links, and other cyclic systems.

Publications

  • Kolokolov I. V., Lebedev V. V., Podivilov E. V., Vergeles S. S. Theory of a random fiber laser. JETP. 146. 1295-1300 (2014).
  • Churkin D. V., Kolokolov I. V., Podivilov E. V., Vatnik I. D., Nikulin M. A., Vergeles S. S., Terekhov I. S., Lebedev V. V., Falkovich G., Babin S. A., and Turitsyn S. K. Wave kinetics of random fibre lasers. Nature Communications. 2, 6214 (2015).
  • Churkin D. V., Sugavanam S., Vatnik I. D., Wang Z., Podivilov E. V., Babin S. A., Rao Y., and Turitsyn S. K.. Recent advances in fundamentals and applications of random fiber lasers. Advances in Optics and Photonics. 7, 516 (2015).

 

2014

Generation of multicolor dissipative soliton complexes in a fiber laser

New scheme of fiber laser has been proposed, designed and implemented. It is shown to be able generating solitons of a new type: Raman dissipative solitons generated by means of Raman conversion of conventional dissipative solitons in a fiber laser cavity. The noisy Raman pulse becomes a coherent dissipative soliton  due to the weak feedback provided at the Stokes shifted wavelength. It has been shown that the proposed scheme may be extended to the next Stokes orders thus forming multicolor soliton complexes that are very perspective for applications in coherent optical communications and biomedical diagnostics.

  • A. E. Bednyakova, S. A. Babin, D. S. Kharenko, E. V. Podivilov, M. P. Fedoruk, V. L. Kalashnikov, A. A. Apolonski. Evolution of dissipative solitons in a fiber laser oscillator in the presence of strong Raman scattering. Opt. Express. 21(18) 20556-20564 (2013)
  • S. A. Babin, E. V. Podivilov, D. S. Kharenko, A. E. Bednyakova, M. P. Fedoruk, V. L. Kalashnikov, A. Apolonski. Multicolour nonlinearly bound chirped dissipative solitons. Nature Communications. 5, 4653 (2014)
  • S. A. Babin, E. V. Podivilov, D. S. Kharenko, A. E. Bednyakova, M. P. Fedoruk, O.V.Shtyrina, V. L. Kalashnikov, A. Apolonski. SRS-driven evolution of dissipative solitons in fiber lasers. Chapter in book “Nonlinear optical cavity dynamics”, ed. by P.Grelu, Wiley-VCH Verlag, 2014 (in press)

High-efficiency random fiber laser

New scheme of Raman fiber laser with random distributed feedback via Rayleigh backscattering in a short fiber has been proposed and realized [1,2]. It exhibits record absolute optical efficiency (about 70%) for generation of the Stokes wave at 1.3 micron under the optical pumping of ~10 W at 1.1 micron. The generated spectrum has no mode structure. Such a modeless radiation is very attractive for applications in low-coherence optical tomography and laser displays. These results are included in the review paper [3] and are selected by OSA as one of the important achievement in optics in 2014 [14].  

  • I. D. Vatnik, D. V. Churkin, S. A. Babin, ”Power optimization of random distributed feedback fiber lasers,” Opt. Express. 20(27), 28033-28038 (2012)
  • I. D. Vatnik, D. V. Churkin, E. V. Podivilov, S. A. Babin. High-efficiency generation in a short random fiber laser. Laser Phys. Lett. 11 (7), 075101 (2014)
  • S. K. Turitsyn, S. A. Babin, D. V. Churkin, I. D. Vatnik, M. Nikulin, E. V. Podivilov. Random distributed feedback fibre lasers. Phys. Reports. 542 (2), 133–193 (2014)
  • Z. Wang, H. Wu, M. Fan, Y. Rao, I. Vatnik, D. Churkin, E. Podivilov, S. Babin, H. Zhang, P. Zhou, H. Xiao, X. Wang. Random fiber laser: simpler and brighter. Optics and Photonics News, N12: OSA Special Issue “Optics in 2014”, 30 (2014)

 

2013

Laminar-turbulent transition for light waves in fiber laser

A transition from laminar to turbulent state of light has been observed, in analogy with hydrodynamic turbulence. It has been demonstrated for a multimode fiber Raman laser as an example that the laminar regime corresponds to the stable generation with narrow linewidth (so called condensate of high coherence) and is observed at low power levels. With increasing power above some critical level, a stepwise transition to turbulent regime takes place due to the loss of spatial coherence. At the transition the generation spectrum broadens abruptly and becomes stochastic. It has been shown that the laminar-turbulent transition in the laser is due to condensate destruction by clustering dark and grey solitons.

Publications:

  • Д.В.Чуркин, С.В.Смирнов, О.А.Горбунов, Е.Г.Турицына, Г.Фалькович, Е.В.Подивилов, С.А.Бабин, С.К.Турицын. Ламинарный и турбулентный режим генерации в непрерывных волоконных лазерах (пригл. докл.). // Материалы Российского семинара по волоконным лазерам 2012 (Новосибирск, 27-30 марта 2012 г.), ИАиЭ СО РАН, 2012,  с.159-160.
  • S.K.Turitsyn, S.A.Babin, E.G.Turitsyna, G.E.Falkovich, E.V.Podivilov,  D.V.Churkin. Optical Wave Turbulence - chapter in book: Advances in Wave Turbulence, edited by V.Shrira and S.Nazarenko), World Scientific Publ., 2013, 296 pp.
  • E.G. Turitsyna, S.V. Smirnov, S. Sugavanam, N. Tarasov, X. Shu, S.A. Babin, E.V. Podivilov, D.V. Churkin, G. Falkovich, S.K. Turitsyn. The laminar-turbulent transition in a fibre laser. Nature Photonics. 7 (4) 783-787 (2013).

Continuous wave fiber optical parametric oscillator with tuning range from 0.92 to 1.2 μm

An all-fiber scheme of the optical parametric oscillator (FOPO) pumped by a CW Ytterbium-doped fiber laser has been proposed and realized. A birefringent photonic crystal fiber is used as a nonlinear medium. The FOPO tuning range of 0.92 - 1.2 μm is demonstrated at the pump laser wavelength variation within 4 nm (Fig. 1a). Moreover, the tunable FOPO generation below 1 μm has been obtained for the first time. The output power and slope efficiency reach 460 mW and 15%, respectively, for unpolarized pump radiation (Fig. 1b), that is several times higher than that ones previously demonstrated for CW FOPOs with frequency up-conversion.

Publications:

  • Злобина Е.А., Каблуков С.И., Бабин С.А. Непрерывная параметрическая генерация в волоконном световоде с сохранением поляризации // Квантовая электроника.– 2011. – Т. 41, № 9. – С. 794– 800.
  • Злобина Е.А, Каблуков С.И, Бабин С.А. Волоконный оптический параметрический генератор на основе волокна с сохранением поляризации // Спецвыпуск «Фотон-экспресс». – 2011. – №6. – C. 99 – 100.  Материалы конференции ВКВО 2011.
  • Zlobina E.A., Kablukov S.I., Babin S.A. Phase matching for parametric generation in polarization maintaining photonic crystal fiber pumped by tunable Yb-doped fiber laser // J. Opt. Soc. Am. B. – 2012. – Vol. 29, no. 8. – Pp. 1959 – 1967.
  • Zlobina E.A., Kablukov S.I., Babin S.A. CW parametric generation in polarization maintaining PCF pumped by Yb-doped fiber laser // Proc. of SPIE, Vol. 8426 (SPIE Photonics Europe 2012, Brussels, Belgium, April 16–19, 2012). – Paper 842613 (12 p).
  • Zlobina E.A., Kablukov S.I., Babin S.A. Tunable CW all-fiber optical parametric oscillator operating below 1 μm // Optics Express. – 2013. – Vol. 21, no. 6. – Pp. 6777 – 6782.
  • Злобина Е.А., Каблуков С.И. Оптические параметрические генераторы на основе волоконных световодов // Автометрия. – 2013. – Т. 49, № 4. – С. 53 – 78.

 

2012

New regime of high-power femtosecond pulses generations in a Yb-doped fiber laser

It is shown that cavity lengthening of the laser with mode-locking via nonlinear polarization evolution effect in a single-mode (SM) fiber results in unstable or muli-pulse generation because of the excessive polarization rotation (angle ≥ π/2). New cavity scheme has been proposed and realized, in which the processes of mode locking and pulse formation are separated  taking place in short SM fiber and long polarization-maintaining (PM) fiber, correspondingly. This approach offers stable generation of frequency-modulated (chirped) dissipative solitons (DS) in the all-fiber cavity with length up to 120 m. At that, the pulse takes nearly rectangular shape and is dechirped by an external compressor by ~200 times (to ~200 fs). Maximum DS energy for PM fiber with 5.5 micron core amounts to ~ 25 nJ, that is by order of magnitude higher than in known variants of all-fiber schemes. It has been found that the pulse energy doesn’t grow at cavity lengthening above 30 m due to Raman effect that limits the energy of DS but does not destroy it. It has been shown that the threshold of the Raman conversion can be increased by means of fiber core diameter enlargement.

Publications:

  • D. S. Kharenko, E. V. Podivilov, A. A. Apolonski, and S. A. Babin. 20 nJ 200 fs all-fiber highly chirped dissipative soliton oscillator. Optics Letters. 37(19), 4104-4106 (2012).
  • D. S. Kharenko, O. V. Shtyrina, I. A.Yarutkina, E. V. Podivilov, M. P. Fedoruk, S. A. Babin. Generation and scaling of highly-chirped dissipative solitons in an Yb-doped fiber laser. Las. Phys. Lett. 9(9), 662-668 (2012).
  • D. S. Kharenko, O. V. Shtyrina, I. A. Yarutkina, E. V. Podivilov, M. P. Fedoruk, S. A. Babin. Highly chirped dissipative solitons as a one-parameter family of stable solutions of the cubic-quintic Ginzburg-Landau equation. JOSA B. 28(10), 2314-2319 (2011).
  • D. S. Kharenko, E. V. Podivilov, A. A. Apolonski, S. A. Babin, New effects at cavity lengthening of an all-fiber dissipative soliton oscillator. Photonics Global Conference 2012, Conf. Proceedings, paper 3-3F-2 (invited).

Broadening mechanisms and generation spectrum shape in ytterbium doped fiber lasers

An adequate model describing generation spectrum broadening for CW Ytterbium-doped fiber lasers has been developed. It is theoretically and experimentally shown that spectral shape of the radiation, consisting of multiple modes with Gaussian statistics generated in relatively short fiber laser cavity (when group velocity dispersion is negligible), is defined by an effect of self-phase modulation and is described by hyperbolic secant function.  At that, the width of the generation spectra grows linearly with increasing laser power in the range 1 - 12 W, until it becomes comparable with the width of the output fiber Bragg grating reflection spectrum. This broadening law differs essentially from the square root growth typical for turbulent broadening of the generation spectrum in Raman fiber lasers, where dispersion is important. The developed model allows one for the first time to evaluate output characteristics of an ytterbium fiber laser using its cavity parameters.

Publications:

  • S. I. Kablukov, E. A. Zlobina, E. V. Podivilov, and S. A. Babin, Output spectrum of Yb-doped fiber lasers, Opt. Lett. 37(13), 2508-2510 (2012).
  • A. G. Kuznetsov, E. V. Podivilov, S. A. Babin. Spectral broadening of incoherent nanosecond pulses in a fiber amplifier. JOSA B, 29(6), 1231-1236 (2012).
  • A.V. Denisov, A. G. Kuznetsov, D. S. Kharenko, S. I. Kablukov, and S. A. Babin. Frequency doubling and tripling in a Q-switched fiber laser. Laser Physics, 21(2), 277-282 (2011).
  • S. I. Kablukov, E. A. Zlobina, E. V. Podivilov, S. A. Babin. Modeling and measurement of ytterbium fiber laser generation spectrum”, Proc. of SPIE, Vol. 8433: Laser Sources and Applications (SPIE Photonics Europe 2012 Conf.), T. Graf; J. I. Mackenzie; H. Jelinková; J. Powell, eds., paper 843305 (2012).

 

2011

Multi-wavelength and tunable generation of a random disrtributed feedback fiber laser

New regimes of a random distributed feedback (RDFB) fiber laser based on Rayleigh scattering (RS) have been obtained: multi-wavelength (22 lines in 1550-1570 nm range with ~100 GHz spacing ) and tunable (continuous tuning  of single line in 1535-1570 nm range). It has been shown this RS-based  RDFB laser outperforms in its basic characteristics conventional Raman lasers with point reflectors  realized in the same fiber.  In particular, it has higher generation efficiency (up to 60%),  much weaker line competition and as a result much better equalized power distribution of  multi-wavelength generation, much more flat (with variations down to  ~0.1 dB) tuning curve, and higher threshold for the second order Stokes wave that results in power enhancement for the first Stokes wave. A simple model has been developed that describes well the output characteristics of the  RS-based  RDFB laser. It has been shown that the lasing mechanism of the RDFB laser has principal difference from that in conventional lasers.

Publications:

  • E. El-Taher, P. Harper, S. A. Babin, D. V. Churkin, E. V. Podivilov, J. D. Ania-Castanon, and S. K. Turitsyn. Effect of Rayleigh-scattering distributed feedback on multiwavelength Raman fiber laser generation. Opt. Lett. 36 (2), 130-132 (2011).
  • S. A. Babin, A. E. El-Taher, P. Harper, E. V. Podivilov, S. K. Turitsyn. Tunable random fiber laser. Phys. Rev. A 84(2), 021805(R) (2011).
  • S.A. Babin, A.E. El-Taher, P. Harper, E.V. Podivilov, D.V. Churkin, S.K. Turitsyn, Effect of Rayleigh-scattering distributed feedback in multi-wavelength and tunable Raman fibre lasers, European Conference and Exposition on Optical Communications - ECOC 2011 (18-22 Sept 2011, Geneva). Conf. Proc., paper Th.12.LeCervin.7
  • S.A. Babin, A.E. El-Taher, P. Harper, D.V. Churkin, E.V. Podivilov, S.K. Turitsyn. Spectral performance of multi-wavelength and tunable Raman fiber lasers based on the Rayleigh-scattering distributed feedback (invited paper). 20th International Laser Physics Workshop - LPHYS’11 (July 11–15, 2011, Sarajevo, Bosnia and Herzegovina). Program, paper 8.1.1.
  • С.А. Бабин. Волоконные лазеры со случайной распределенной обратной связью на рэлеевском рассеянии (приглашенный доклад). Фотон-экспресс (Спецвыпуск: 3 Всероссийская конференция по волоконной оптике, г. Пермь, 12-14 октября 2011 г.), 2011, т. 94, № 6, с.92-93.

 

2010

Ultra-long fiber lasers with random disrtributed feedback

Laser generation of the fiber Raman laser with a record cavity length of 270 km has been obtained. It has been found that new physical effect becomes important in such ultra-long lasers:  Rayleigh scattering (RS) on random refractive index inhomogeneities of sub-micron scale may form a cavity with random distributed feedback. The length of 270 km is found to be an upper limit of  fiber cavity between two point reflectors. Above this length the effect of RS-based distributed feedback starts to dominate over the reflection from point mirror (fiber Bragg grating) forming the linear cavity.

It has been discovered that stationary lasing  via RS-based random distributed feedback (RDFB) only (without point reflectors)  is possible demonstrating narrowband (<1.5 nm) outpu t with high efficiency (30%) in a standard telecommunication (passive) fiber with length of 83 km. the developed  RDFB laser has much better characteristics than traditional «random» lasers realized in a bulk disordered media. In particular, it has narrow spectrum, high temporal and spatial stability, and high quality of the output beam.  And in contrast to conventional fiber lasers with regular reflectors (both point and distributed), the RS-based RDFB fiber laser delivers “modeless” (continuous-spectrum) radiation and has no principal limitations of the cavity lengths. At that, it may be continuously tunable and generate multiple lines in different spectral domains without any mirror or wavelength selector. The unique properties of the RDFB fiber lasers offer new class of laser sources with great potential both in fundamental research and applications, specifically in long-haul optical fiber communications and distributed sensor systems.

Publications:

  • S. K. Turitsyn, J. D. Ania-Castañón, S. A. Babin, V. Karalekas, P. Harper, D. Churkin, S. I. Kablukov, A. E. El-Taher, E. V. Podivilov, and V. K. Mezentsev. “270-km ultralong Raman fiber laser”, Phys. Rev. Lett., 2009, v. 103, paper 133901.
  • S.K. Turitsyn, S.A. Babin, A.E. El-Taher, P. Harper, D.V. Churkin, S.I. Kablukov, J.D. Ania-Castañón, V. Karalekas, E.V. Podivilov. “Random distributed feedback fibre laser”, Nature Photonics, 2010, v.4, N4, p.231-235.

 

2009

Efficient second harmonic generation in a multimode Raman fiber laser

Efficient second harmonic generation (SHG) in a randomly polarized multimode Raman fiber laser (RFL) in a periodically poled LiNbO3 crystal has been demonstrated. The SHG power is shown to increase linearly with increasing RFL  power even though the RFL spectral width becomes much larger than the acceptance width of the crystal. The simulation has shown that the sum frequency mixing processes between modes within the RFL generation spectrum make the main contribution to that. Moreover, the multimode SHG efficiency appears to be twice higher than in the single-frequency case, which is caused by the stochastic (turbulent) character of the RFL output spectrum broadening. When the RFL spectral width becomes larger that the acceptance width of the crystal, the enhancement coefficient decreases. As a result, a new fiber laser source generating > 60 mW at 655 nm and possessing appreciable advantages over conventional lasers has been realized.

Publications:

  • S. I. Kablukov, S. A. Babin, D. V. Churkin, A. V. Denisov, D. S. Kharenko. Frequency doubling of a broadband Raman fiber laser to 655 nm, Optics Express, 2009, v.17, N8, p. 5980-5986.
  • S. I. Kablukov, S. A. Babin, D. V. Churkin, A. V. Denisov, D. S. Kharenko. Frequency doubling of a Raman fiber laser. Laser Physics, 2010, v.20, N2, p.334-340.
  • Бабин С.А., Каблуков С.И. Генерация второй гармоники излучения волоконных лазеров. Фотон-Экспресс, cпецвыпуск: Сборник трудов Всероссийской конференции по волоконной оптике 2009. – №6. – 2009. – c.56-57.
  • Харенко Д.С., Денисов А.В., Бабин С.А., Каблуков С.И., Чуркин Д.В. Удвоение частоты волоконного фосфосиликатного ВКР-лазера. Третий Российский семинар по волоконным лазерам (Уфа, 31 марта- 2 апреля 2009 г.). Материалы семинара, с.79-80.

 

2007-2008

Fiber lasers with broad tuning range

New lasers with broad range of wavelength tuning in all-fiber performance have been developed. Wavelength selection has been performed by means of fiber Bragg gratings (FBGs). A new technique of synchronous tuning of several FBGs forming a laser cavity has been proposed and realized. The continuous tuning range of 45, 65, and 50 nm around wavelengths of 1100, 1550, and 1300 nm for lasers based on Yb-, Er- and P- doped fibers, respectively, has been obtained. In the latter case, synchronous tuning of the both cavities for a phosphosilicate Raman laser and a pump Yb-doped fiber laser has been utilized. It has been shown that the tuning range is limited by a misalignment in the FBG resonant wavelengths arising at strong compression. The possibility of converting the obtained tunable radiation to visible range has been also demonstrated.

Publications:

  • V. A. Akulov, S. A. Babin, S. I. Kablukov, A. A. Vlasov. Fiber lasers with tunable green output, Laser Physics, 2008, v.18, N11, p.1225-1229.
  • Babin S.A., Kablukov S.I., Vlasov A.A. Tunable fiber Bragg gratings for application in tunable fiber lasers. Laser Physics, 2007, v.17, N11, p.1323–1326.
  • Babin S.A., Churkin D.V., Kablukov S.I., Rybakov M.A., Vlasov A.A. All-fiber widely tunable Raman fiber laser with controlled output spectrum. Opt. Express, 2007, v.15, N13, p.8438-8443.
  • Akulov V.A., Afanasiev D.M., Babin S.A., Churkin D.V., Kablukov S.I., Rybakov M.A., Vlasov A.A. Frequency tuning and doubling in Yb-doped fiber lasers. Laser Phys., 2007, v.17, N2, p.124-129.
  • Абдуллина С.Р., Акулов В.А., Бабин С.А., Власов А.А., Каблуков С.И., Курков А.С., Шелемба И.С. Полностью волоконный иттербиевый лазер, перестраиваемый в диапазоне 45 нм. Квант. электроника, 2007, т.37, N12, с.1146-1148.

Мode structure of the ultra-long Raman fider laser

It is known that laser radiation spectrum consists of a “comb” of spectral components (modes) with frequency difference of ∆=c/2Ldetermined by the length of resonator (L) and speed of light in a medium (c). In the research, the resonator length is increased up to the record value of L=84km in a configuration of Raman fiber laser generating nearby the transparency window (~1,5 microns). It is proven that in accordance with the above formula, the intermode interval goes down to the minimum value of ∆~1 kHz, and the number of the generated modes reaches N~108. Here, the mode structure in a radio-frequency spectrum is observable at a low radiation only. The width of the intermode beating peak determined by relative frequency fluctuations practically does not depend on the length, amounts ~100 Hz at the generation threshold and grows linearly with increasing generation power. At some power level, when the peak width equals to the intermode interval, the mode structure is washed off and the frequency comb converts into a “quasi-continuous” spectrum. The limit power is inversely proportional to the length and amounts to ~100 mW at L=84 km. It is proven that the washing is caused by nonlinear turbulent dephasing resulting from joint action of dispersion and four-wave mixing of a large number of modes generated.

Publications:

  • S. A. Babin, E.V. Podivilov. New physical effects in ultra-long Raman fiber lasers. Laser Physics, 2008, v.18, N2,p.122-128.
  • S. A. Babin, V. Karalekas, E. V. Podivilov, V. K. Mezentsev, P. Harper, J. D. Ania-Castaсуn and S. K. Turitsyn. Turbulent broadening of optical spectra in ultralong Raman fiber lasers. Phys. Rev. A, 2008, v. 77(3), 033803 (5p.).
  • Babin S.A., Karalekas V., Harper P., Podivilov E.V., Mezentsev V.K., Ania-Castañón J.D., Turitsyn S.K. Experimental Demonstration of Mode Structure in Ultra-Long Raman Fibre Lasers. Opt. Lett., 2007, v.32, N9, p.1135-1137.
  • Karalekas V., Ania-Castañón J.D., Harper P., Babin S.A., Podivilov E.V., Turitsyn S.K. Impact of nonlinear spectral broadening in ultra-long Raman fibre lasers. Opt. Express, 2007, v.15, N25, p.16690-16695.

Тurbulent broadering of generation spectral in Raman fiber lasers

A mechanism of spectral broadening of the generation line in Raman  fiber lasers has been identified after detailed experimental and theoretical analysis of the role of various nonlinear effects: Raman gain saturation, stimulated Brillouin scattering, four wave mixing. It has been proved that the four wave mixing between multiple longitudinal modes of laser cavity which  number amounts to ~106, results in stochastic behavior of  their phases and amplitudes as well as in generation of new spectral components. A self-consistent analytical theory has been developed  on the base of the wave kinetic equation earlier used for description of weak wave turbulence in surface, acoustic, spin and other waves. The theory describes well the experimental spectrum (of hyperbolic secant shape) and its power broadening (of square-root law) without any fitting parameter. The discovered turbulent broadening  of the Raman fiber laser spectrum is a unique example of one-dimensional wave turbulence in optics.

Publications:

  • S. A. Babin, D. V. Churkin, A. E. Ismagulov, S. I. Kablukov, E. V. Podivilov, Turbulence-induced square-root broadening of the Raman fiber laser output spectrum. Opt. Lett., 2008, v.33, N6, p.633-635.
  • Бабин С.А., Исмагулов А.Е., Каблуков С.И., Подивилов Е.В., Чуркин Д.В. Исследование рассеяния Мандельштама-Бриллюэна в фосфосиликатном волокне и его влияния на генерацию ВКР-лазера. Квант. электр., 2007, т.37, N5, с.495-499.
  • Babin S.A., Churkin D.V., Ismagulov A.E., Kablukov S.I., Podivilov E.V. FWM-induced turbulent spectral broadening in a long Raman fiber laser. JOSA B, 2007, v.24, N8, p.1729-1738.
  • Babin S.A., Churkin D.V., Ismagulov A.E., Kablukov S.I., Podivilov E.V. Broadening of the intra-cavity and output spectra of a Raman fiber laser with a low-Q cavity. Laser Physics, 2007, v.17, N11, p.1279–1285.
  • Babin S.A., Churkin D.V., Kablukov S.I., Podivilov E.V. Homogeneous Raman gain saturation at high pump and Stokes powers. J. Opt. Soc. Am. B, 2006, v.23, N8, p.1524-1530.
  • Babin S.A., Churkin D.V., Ismagulov A.E., Kablukov S.I., Podivilov E.V. Spectral broadening in Raman fiber lasers. Opt. Lett., 2006, v.31, N20, p. 3007-3009.