Bulletin of the Lebedev Physics Institute最新文献

We report a method for measuring complex coupling coefficients in a ring resonator of a laser gyroscope. It is shown how, using the results of the measurements, to predict the values of the lock-in threshold and nonlinear distortions of the scale factor of a laser gyroscope at the stage of assembly and adjustment of the ring resonator and, in particular, to detect the presence of dust particles in the working areas of the mirrors. The possibilities of using this method to optimize the process of sputtering multilayer mirrors of a laser gyroscope are discussed.

Disk lasers are a promising configuration that can produce high output power with high spatial quality of radiation due to efficient heat removal from the active region. An important task in the design of disk lasers is to achieve efficient pumping with high gain uniformity across the active region. A new multipass pumping scheme is proposed. The pumping distribution in a Yb:YAG/YAG disk-shaped composite ceramic active element has been numerically simulated and experimentally investigated. It is shown that for such a scheme with 12-channel pumping, the distribution of absorbed pump power with an inhomogeneity of maximum 12.6% can be achieved at a pumping efficiency of 80%.

We report a theoretical and experimental study of the effect of up-conversion on the efficiency of continuous-wave generation of the fundamental TEM₀₀ mode in a YLF:Nd³⁺ laser longitudinally pumped by laser diode radiation. It is shown that up-conversion is not the reason for the dependence of the single-mode output power of a YLF:Nd³⁺ laser on the output mirror reflectance at a constant pump power.

A laser amplifier based on an active element in the shape of a Yb:YAG slab is developed. It combines the propagation of an amplified elliptical beam without internal reflections, the use of high-brightness diode pump channel combining, and a heat sink made of silicon carbide. Its laser characteristics and factors limiting the output pulse energy are studied. It is shown that the application of an active element with gradient doping ensures stable operation of the laser head at pump powers of ∼0.5 kW. The use of signal radiation diverging along one axis compensates for the effect of reducing the output cross section of the amplified beam; as a result, a gain of G = 4 is ensured with a beam quality factor M² < 1.4.

The proposed fiber-optic device is an array of tapering cores in a common cladding. Possible applications of the device for radiation summation in multielement laser systems are discussed. The criterion is specified for the formation of the device parameters to obtain optically independent channels, which makes it possible to produce a narrow radiation beam in the far zone. Analytical expressions are derived for the radiation field in the far zone and the parameters of the device for obtaining a close-to-diffraction divergence. This device allows an unlimited increase in the number of emitters to increase the radiation power in a narrow beam.

We report a developed methodology for studying the main parameters and identifying the features of chirped volume Bragg gratings (CVBGs). The results of diagnostics of the first fused silica CVBG samples inscribed by femtosecond laser pulses using a phase mask are presented: the linear absorption coefficient, phase and polarization distortions arising during grating inscription, and spectral and dispersion characteristics are studied. The results of the studies indicate the prospects for using gratings of this type in high-average-power laser systems.

We report the results of fabrication works on single-frequency tunable semiconductor laser modules for a wavelength of 1550 nm, with an external cavity being based on fiber Bragg gratings formed in a single-mode fiber. Tuning of the radiation wavelength using a piezoceramic element is considered. The laser modules are capable of generating dynamically stable single-frequency radiation with side mode suppression of more than 40 dB, a lasing line width of 100 kHz, and an output optical power of higher than 50 mW. The wavelength tuning of the emission spectrum of the laser module is 2 nm.

We report an investigation of a semiconductor disk laser (SDL) based on an InGaP/AlGaInP heterostructure emitting at a wavelength near 640 nm under in-well pumping by a pulsed rhodamine 6G dye laser with an emission wavelength of 601 nm. Use is made of structures with 25 quantum wells arranged in depth with a period of 193 nm. In a structure with a built-in Bragg mirror, a power of 3.5 W is reached at a wavelength of 642 nm with a slope efficiency of 7% with respect to the absorbed pump power. The achieved second harmonic power at a wavelength of 321 nm is approximately 30% of the maximum SDL power at the fundamental frequency. Under pumping above 250 W, the structure is destroyed due to strong adiabatic heating of the GaAs growth substrate. In a structure with a deposited broadband dielectric mirror, it is possible to reduce the adiabatic heating factor, implement double-pass pumping, and, accordingly, increase the supplied pump power. This makes it possible to obtain a pulse power of higher than 70 W at a wavelength of 645.5 nm with a slope efficiency of over 17%.

A system of detectors for the front of extensive air showers (EAS) was set up at the Tien Shan High-Altitude Station of the Lebedev Physical Institute (LPI), which has a high time resolution and is designed to determine the arrival directions of shower-generating cosmic-ray particles. Algorithms and software were developed for analyzing information coming from the station to obtain estimates of the azimuth and zenith angles for each registered shower. This information makes it possible to investigate a large-scale distribution of the arrival points of primary cosmic ray particles on the celestial sphere.

We discuss the suitability of few-body exclusive W boson decays for precise measurements of its mass and width. We show that the decay modes of this kind have extremely small relative widths, which excludes any possibility of their practical use.