Andrey Petrovich Zinoviev

Optical properties and efficient laser oscillation at 2066 nm of novel Tm:Lu 2 O 3 ceramics

Structural, optical, and spectroscopic properties of novel Tm3+:Lu2O3 ceramics are studied. The average grain size is determined to be ~0.54-0.56 μm. The absorption spectra show good opportunities for diode pumping at 796 nm and 811 nm. The ceramics have high mid-IR transmittance of up to 7 μm. Strong luminescence lines are measured at 1942 nm, 1965 nm, and 2066 nm. CW laser operation at 2066 nm with an output power of up to 26 W and a slope efficiency of 42% is obtained. Q-switched operation with a pulse duration of 100-150 ns and a repetition rate of 5-10 kHz is achieved.

250-W average-power Nd:YAG laser with self-adaptive cavity completed by dynamic refractive-index gratings

A high average power laser oscillator with a cavity completed by a nonlinear mirror formed by refractive index gratings which accompany population gratings induced in Nd:YAG laser crystals by generating beams themselves is investigated numerically and experimentally. The role of different noise sources at the initial stage of nonlinear cavity formation is studied. The adaptation of the cavity formed by nonlinear dynamic mirrors to intracavity distortions is demonstrated. The generation of beams with average power up to 250 W, near-diffraction-limited divergence, and long coherence length has been achieved.

High-average-power solid state lasers with cavity formed by self-induced refractive index gratings

We present a self-starting Nd:YAG laser-oscillator with cavity formed by refractive index gratings and gain gratings accompanying population gratings which are induced in the laser crystal by generating beams themselves. The spatio- temporal and spectral characteristics of the laser including two Nd:YAG-amplifiers, a saturable absorber and a Sagnac interferometer are investigated. The laser-oscillator with a nonlinear mirror has displayed self-adaptivity to strong thermally induced intracavity distortions. Generation of single mode beams with up to 60 W average power and near- diffraction limited quality has been achieved.

Nd:YAG laser with cavity formed by population inversion gratings

New principles of distributed feedback lasers with cavity formed by refractive index gratings induced in the laser crystal by generating beams themselves have been discussed. Different geometries of the cavity (linear, loop and multi- loop) with Nd:YAG crystal have been investigated experimentally. The oscillator with a nonlinear mirror has displayed self-adaptivity to strong intracavity distortions. Generation of single transverse mode beams with near- diffraction limited quality in millisecond pulse-repetitive regime with 12 W average power has been achieved in the oscillator with single Nd:YAG amplifier.

Dynamics of refractive index changes in Tm-doped crystals Tm:YAG and Tm:YLF, and ceramics Tm:Lu 2 O 3

Strong refractive index changes (RICs) of electronic origin (due to polarizability differences in the excited and unexcited activator ions) have been experimentally and theoretically studied recently in the case of the laser crystals and glasses doped by Nd3+ and Yb3+ ions when they are intensively pumped [1,2]. Interferometric and grating testing methods were developed for the registration of the index changes and the separation of the electronic and thermal contributions, and excited-state absorption measurements were performed to estimate the polarizability changes with the aid the Clausius-Mosotti relation. This present communication is devoted to the interferometric measurements of the index changes in Tm-doped laser materials: crystals Tm:YAG and Tm:YLF, and ceramics Tm:Lu2O3 under laser pumping.

Silicon-containing polymers for non-linear optics

A variety of novel poly[ethynediyl-arylidene-ethynediyl-silylene]s (PEAES), including those containing hypercoordinate silicon atom as well as donor and acceptor groups, has been synthesized. The presence of hypercoordinate silicon favours high values of fast Kerr-type non-linearities, and the incorporation of amide groups gives rise to good optical quality nanocomposites in a silica matrix. The inorganic-organic hybrid sol-gel film incorporating 5–14 mass% of the polymer containing pentacoordinate silicon showed Reχ (3) = −9.5 ×10−11 esu. The predominant rôle of the electron nonlinear mechanism has been demonstrated by using test beams with linear and circular polarizations. The photorefractive properties of composites based on PEAES as optical chromophores, poly(9-vinylcarbazole) as photoconductor, N-ethylcarbazole and phenyltrimethoxysilane as plasticizer, and fullerenes as charge generators have been investigated. The nonlinear optical effects, including four-wave mixing and two-beam coupling were studied at 633 nm without preliminary electric poling. The photorefractive origin of the refractive index changes was confirmed by the high two-beam gain under an externally applied electric field. Refractive index gratings affording two-beam gain can also be written under zero field conditions. To explain this unique property of the materials it is suggested that chromophore orientation asymmetry arises either during film formation or is induced by the longitudinal intensity gradient.

Self-starting 100-W-average-power laser with a self-adaptive cavity

The numerical and experimental investigation of a self- starting Nd:YAG laser oscillator with a cavity completed by population gratings induced in the laser crystal by generating beams themselves are reported. The spatio- temporal characteristics of the laser comprising three Nd:YAG amplifiers and a saturable absorber were investigated. The generation of single mode beam with an average power of as large as 100 W and high quality was achieved.

Single-mode Nd:YAG laser with cavity formed by population gratings

Q-switched regimes of the nanosecond pulse-periodic Nd:YAG laser with dynamic cavity formed with participation of dynamics holographic gratings in laser elements have been investigated. A Sagnac interferometer was applied as a laser cavity mirror for angular selection of initial radiation. As a passive Q-switch, we used saturable absorber crystal LiF:F2-, which increased total intracavity diffraction efficiency of dynamic gratings completing the cavity. Self-pumped phase conjugation in Nd:YAG amplifier and LiF:F2- absorber provided adaptive properties of the cavity. The peak power of generated beam with diffraction quality exceeded 17.5 MW and the average power achieved 50 W.

Non-resonant pump-induced refractive index changes and non-degenerate two-wave mixing in Nd3+ and Yb3+ doped laser materials

Modeling and experiments of two-wave mixing and energy-transfer based on accurate measurements of pump-induced refractive index variations were performed. Results indicate that energy transfer exceeding 50% is possible under high pumping conditions.

Continuous-wave and pulsed diode-pumped solid-state lasers with reciprocal dynamic holographic cavity

In this report, we present laser systems with the dynamic holographic cavity based on cw diode pumped Nd:YVO/sub 4/ crystals and repetitively pulsed diode pumped Nd:YAG crystals. The spatial and temporal characteristics of the generated laser beams were also studied experimentally.