Valerii I Kovalev

Suppression of stimulated Brillouin scattering in high-power single-frequency fiber amplifiers

The effect of temperature variation along a high-power fiber amplifier on the stimulated Brillouin scattering (SBS) threshold is considered theoretically. We show that for an end-pumped rare-earth-doped double-clad fiber the inhomogeneous distribution of temperature, which is caused by the absorption of pump radiation, may result in total suppression of SBS even for output powers well above 200 W.

Waveguide-induced inhomogeneous spectral broadening of stimulated Brillouin scattering in optical fiber.

We provide direct experimental evidence of waveguide-induced inhomogeneous spectral broadening of stimulated Brillouin scattering (SBS) in optical fiber. It is shown that the SBS spectral width and gain depend on the numerical aperture for both single-mode and multimode fibers, the functional dependencies of which are in good agreement with our model description of the phenomenon.

Threshold for stimulated Brillouin scattering in optical fiber.

It is important to note that the expression for Gth contains the explicit dependence on fiber material characteristics. Results of our calculations are in reasonably good correspondence with proper measurements in silica fibres, which we have found in the literature and have done ourselves in fibre-samples without and with cavity feedback.

Sbs self-phase conjugation of CW Nd:YAG laser radiation in an optical fibre

Abstract High fidelity, polarised, optical phase conjugation via stimulated Brillouin scattering of CW laser radiation in a multimode silica fibre is reported. A power threshold of ∼70 mW and reflectivity of 70% were obtained in a 4.23 km length of fibre with a Nd:YAG laser.

Trends in stimulated Brillouin scattering and optical phase conjugation

An overview on current trends in stimulated Brillouin scattering and optical phase conjugation is given. This report is based on the results of the “Second International Workshop on stimulated Brillouin scattering and phase conjugation” held in Potsdam/Germany in September 2007. The properties of stimulated Brillouin scattering are presented for the compensation of phase distortions in combination with novel laser technology like ceramics materials but also for e.g., phase stabilization, beam combination, and slow light. Photorefractive nonlinear mirrors and resonant refractive index gratings are addressed as phase conjugating mirrors in addition.

The dynamics of a SBS fibre laser: the nature of periodic spiking at harmonics of the fundamental oscillation frequency

We show that periodic oscillatory emission in a fibre SBS laser occurring at harmonics of the reciprocal of the round trip time through the fibre, otherwise the fundamental oscillation frequency, is the consequence of longitudinal mode selection due to hole burning in the spectrum of the Brillouin gain, recently shown to be inhomogeneous in optical fibres.

Diffraction limited output from a CW Nd: YAG master oscillator/power amplifier with fibre phase conjugate SBS mirror

Abstract A CW Nd:YAG master oscillator power amplifier with fibre based SBS phase conjugate mirror is reported. A four-pass amplifier configuration is employed to compensate pump induced thermal lens and birefringence in the amplifier rod in conjunction with a fibre phase conjugator to achieve diffraction limited output beam quality. Maximal attainable gain of ∼1.9 for the system is obtained. Application of the technique to diode pumped systems for high gain and high power delivery is proposed.

Threshold for stimulated Brillouin scattering in optical fibres

It is important to note that the expression for Gth contains the explicit dependence on fiber material characteristics. Results of our calculations are in reasonably good correspondence with proper measurements in silica fibres, which we have found in the literature and have done ourselves in fibre-samples without and with cavity feedback.

Temporally stable continuous-wave phase conjugation by stimulated Brillouin scattering in optical fiber with cavity feedback

Temporally stable high-fidelity optical phase conjugation by stimulated Brillouin scattering of cw laser radiation is achieved in multimode silica fiber with cavity feedback. A power threshold of approximately 500 mW and a reflectivity of 70% were obtained in a 340-m-long fiber with a cw Nd:YAG laser.

Abnormally low threshold gain of stimulated Brillouin scattering in long optical fiber with feedback

We show that in the generation of stimulated Brillouin scattering (SBS) in long (> 1 km) fiber, the threshold for observing coherent Stokes emission occurs at notably lower gain than the classical lasing threshold gain for SBS. The effect is due coherent regenerative amplification of strong spontaneous Brillouin scattering, which occurs in the presence of feedback. The magnitude of the effect scales with the length of interaction.