Andrei S Kurkov

Multiwavelength generation in a random distributed feedback fiber laser using an all fiber Lyot filter

Multiwavelength lasing in the random distributed feedback fiber laser is demonstrated by employing an all fiber Lyot filter. Stable multiwavelength generation is obtained, with each line exhibiting sub-nanometer line-widths. A flat power distribution over multiple lines is obtained, which indicates that the power between lines is redistributed in nonlinear mixing processes. The multiwavelength generation is observed both in first and second Stokes waves.

All-fiber passively Q-switched ytterbium laser

In this paper, we propose an all-fiber and simultaneously low-cost solution, where a double-clad Yb-doped fiber laser employing Sm-doped fiber as a saturable absorber results in passive Q-switch operation, and in association with a 6 W-diode pumping allows generation of gigantic pulses with 30 W/2.5 W-peak/average power contrast and excellent pulse-to pulse stability.

Dynamics of All-Fiber Self-Q-switched Ytterbium/Samarium Laser

We have explored self-Q-switched operation of the fiber laser comprising ytterbium and samarium fibers in the cavity. Regular pulses are attainable at any wavelength within the gain spectrum. Dynamics of pulsation involves polarization mode switching.

Stable self-pulse behavour of two-core Yb/Sm fiber laser

Q-switched fiber lasers operating intense linear polarized pulses with a narrow linewidth at ∼1.06 µm are of great interest for frequency doubling and suit various applications in medicine, range finding, remote sensing, and optical parametric oscillators. Recently we reported an all-fiber and simultaneously low-cost solution, where a double-clad Yb-doped fiber laser employing Sm-doped fiber as a saturable absorber (SSA) exhibited passive Q-switch operation [1]. There were two drawbacks associated with that laser: sophisticated polarization dynamics explained by a specific Q-switching mechanism that involves the polarization switching [1] and rather broad laser spectrum (∼1nm) that is however typical for standard double-clad fiber lasers with Watt-scale pumping. The latter feature is attributed to the presence of FWM between the laser longitude modes that lead to the broadening of the laser line within the whole FBG reflectivity spectrum. One of the ways to overcome these limitations is to use a multi-core Yb-doped fiber that provides simultaneously higher birefringence for maintaining the linear polarization and a lower concentration of the light energy in each fiber core preventing inter-mode FWM in the laser cavity. It was recently demonstrated [2] that the use of multi-core laser in combination with a multimode fiber Bragg grating (MFBG) written in a gradient fiber is able to provide phase locking between lasing in different fiber cores. Here we report a stable periodic behaviour observed with a two-core Yb-doped fiber laser supplied simultaneously by the MFBG and SSA. Interesting specific features observed in our experiment are an unusually narrow laser spectrum, perfect linear polarization and complicated spatialtemporal behavior of the laser radiation in the far field.

Self-Q-switched fiber lasers with Rayleigh/SBS ring mirrors

Passive Q-switching in fiber lasers can be caused by cooperative dynamics of linear Rayleigh backscattering (RS) and Stimulated Brillouin Scattering (SBS) in a fiber configuration. We give a clear physical insight into the RS-SBS mechanism and present new experiments with low- and high-power self-Q-switched fiber lasers. A 15-ns self-stating periodic pulse generation with a peak power up to 40-300 W has been investigated with an Er-doped fiber laser pumped at 20-160 mW from a laser diode. The generation of Q-switched pulses occurs with a perfect pulse shape performance without emitting any parasitic pulse. We have also realized a self Q-switched double-clad Yb-doped fiber laser. For this laser an average/peak power as high as 1.4 W/5 kW has been achieved at a pulse repetition rate in a range of 5-50 kHz and a pulse duration of 5-10 ns.

Spectral characteristics of a Raman fiber laser with temperature-tunable FBGs

In a two-stage phosphosilicate Raman fiber laser (1.26/1.53μm) pumped by Yb-fiber laser (1.08μm), a temperature tuning of FBGs forming Raman cavities has been performed by means of thermoelectric modules based on Peltier elements. Output power and spectral profiles at 1.26μm and 1.53μm have been monitored during such T0-tuning in the range of ±25C corresponding to the FBG wavelength shift of ±0.2nm. The most pronounced effect is that the observed spectral profile at 1.26μm corresponding to the first-stage highly-reflective cavity consists of two splitting components, which become strongly asymmetric while independent T0-tuning of cavity FBGs. A simple model considering spectral broadening with increasing pump power and T0-induced shift between central wavelengths of the FBGs has been developed. The model takes into account wavelength-dependent Raman gain saturation and qualitatively describes the observed effects of the splitting and asymmetry with T0-tuning. It is also demonstrated, that the studied spectral broadening and shift lead to the effective “bleaching” of the highly-reflective cavity, so estimated integral transmission may increase by order of magnitude from minimum transmission ~ 1%, corresponding to central FBG wavelength.

A 1.65-{mu}m fibre Raman amplifier

A fibre Raman amplifier operating at a wavelength of 1.65-μm is fabricated. A two-stage phosphosilicate fibre Raman converter of 1.53-μm radiation for pumping the Raman amplifier is designed and tested. The amplifier pumped by a phosphosilicate fibre Raman converter can operate with a maximum of the gain band ranging from 1.6 to 1.7 μm. A fibre with a core of a high (25%) molecular content of GeO2 serves as an active medium for the Raman amplifier. The gain obtained for different powers of the input signal is 22 — 25 dB. Our calculations show that the use of a standard telecommunication fibre (with a lower content of GeO2) allows one to increase the gain in this scheme by reducing fibre splicing losses.

Efficient CW Ho/sup 3+/-doped silica fibre laser operating at 2 /spl mu/m

Summary form only. We pump the Ho/sup 3+/-doped fiber laser into the core using a high-power double-clad Yb/sup 3+/-doped fiber laser operating at 1.15 /spl mu/m. This wavelength corresponds to a sufficiently strong absorption band of Ho/sup 3+/ ions due to the laser transition. Also we use a Bragg grating with a resonance wavelength of 2 /spl mu/m as the input mirror of the laser.

Single-mode fiber waveguides with the point of zero chromatic dispersion displaced to the wavelength of 1.55 μm

A single-mode fiber waveguide with zero chromatic dispersion at the wavelength of 1.55 μm was made. This fiber had a refractive index profile which was nearly triangular. The optical losses at 1.55 μm were below 0.3 dB/km.