Vasilii M. Klementyev

Frequency synthesis of the 0.63 μm radiation by mixing of three IR radiation frequencies in a gas

The present paper offers a scheme of synthesis and measurement of frequency of 0.63 μm laser radiation based on mixing of three frequencies of a cascade He-Ne laser generating simultaneously the three lines: 3.39, 2.39, and 1.15 μm. Reported is an experimental observation of coherent radiation with a wavelength of 0.63 μm arising in mixing of the three frequencies in a gas. The effective frequency transformation was performed at the nonlinear interaction of three fields resonant with coupled transitions in neon. Due to the resonance conditions an efficiency of the frequency transformation in a gas proved to be 8–10 orders higher than that in nonlinear optical crystals.

Comparison of frequency stabilities of the Rb standard and of the He−Ne/CH4 laser stabilized to theE line in methane

AbstractThe paper reports on the production of an optical time standard on the basis of the He−Ne laser stabilized to theE line in methane and on a comparison of its frequency stability with that of the rubidium standard. It is shown that the stability of the optical standard is better than that of the rubidium one. Frequency measurements of theE line gavevE=88373149031.2±1.2 kHz. We have also made new measurements on the frequency of the He−Ne laser stabilized to theF2(2) methane line:

Femtosecond optical clock with the use of a frequency comb

v_F = 88376181602.9 \pm 1.2kHz.

Supercontinuum generation in highly nonlinear optical fibers using Cr:Forsterite laser

A new stage of development of optical clocks and synthesizers is possible with the use of highly stable femtosecond lasers. Using femtosecond lasers and special optical fibres, a highly stable frequency comb covering the frequency interval up to several hundreds of THz with a spacing from 100 MHz to 1 GHz has been developed. Experimental schemes for the femtosecond optical clock based on the He-Ne/CH4 and Nd:YAG/I2 frequency standards are presented. The possibility of using tapered fibres for optical clocks and synthesizers is investigated. It is shown that, depending on their influence on the frequency characteristics of the spectral components of the transmitted radiation, tapered fibres can be used in femtosecond optical clocks and synthesizers.

Investigation of the mode-locked regime in a diode laser by microwave pumping at a current close to the generation threshold

The principles of precision measurement of frequency intervals in optical range with the help of femtosecond lasers are described. An experimental scheme of femtosecond optical clock is described. The characteristics of the basic elements and units of the setup are presented. The results of a broadened spectrum researches with the help of tapered fibers are reported.

Transformation of femtosecond Ti:S laser pulses by a tapered fibers

The spectral characteristics and stability of a frequency of intermode beats of a femtosecond Ti:S laser are investigated. An active method is used to obtain high stability. The frequency stability of intermode beats not lower than 5.8.10-14 rms in 100s is achieved. Possible applications of the setup, such as measurement of large frequency intervals in the optical range, creation of optical frequency synthesizers, etc. are proposed. The physical principles for the creation of an optical clock of a new type using highly stable femtosecond Ti:S laser are considered.

Investigations of the influence of a tapered fiber on spectrum of femtosecond pulses train

We report the recent results of research focused on a new kind of soft matter – the liquid-crystal nanocomposites with controllable mechanical and nonlinear optical properties. These are promising media for implementation of ultra-compact photonic devices and efficient sources of coherent radiation in a wide spectral range. We overview the technology of preparation of nematic-liquid-crystal media saturated with disclination defects. The defects were formed in different ways: by embedding nanoparticles and molecular objects, by exposure to alpha-particle flux. The defect locations were controlled by applying an electric field. We also present and discuss the recently discovered features of nematic-liquid-crystal media: a thermal orientation effect leading to the fifth-order optical nonlinearity, enormous second-order susceptibility revealed by measurements, and structural changes upon exposure to laser radiation. We report on efficient generation of harmonics, sum and difference optical frequencies in nematic-liquid-crystal media. In addition, transformation of laser radiation spectra to spectral supercontinua, and filamentation of laser beams were also observed in nematic-liquid-crystal media. We conclude that most nonlinear optical effects result from changes of the orientational order in the examined nematic liquid crystals. These changes lead to the symmetry breaking and disclination appearances.