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We propose a new operation mode for an atomic force microscope (vertical mode), which can be used to measure the topography and other physical parameters of a surface with deep pores, vertical walls, and significant height differences. The measurement of height in this mode is conducted upon vertical uniform motion of the probe towards the surface. Corresponding AFM images are presented.

Electron-beam lithography and ion etching of GaAs/AlGaAs heterostructures are used to create transistor structures with a qusi-1D ballistic channel and side control gates. A plateau of the conductance quantization is observed up to unusually high temperatures (up to 50 K) along with the hysteresis effect. It is demonstrated that such features are related to the presence of a narrow strip of positive charge in the doped layer in AlGaAs, this strip being the result of the etching in the vicinity of the channel.

We investigated the influence exerted by the radius of the bend of fiber light guides with light-transmitting cores of different diameters on the transformation of the spectrum of longitudinal modes of the semiconductor laser radiation introduced into them. It is shown that the bended segment of the light guide acts as a spectrum selector, and the spectral composition of the radiation at the output of a light guide is different in different spots of the speckle structure.

Measurements of the dispersion parameter (the second derivative of the wave vector with respect to the frequency) of the active waveguide layer of semiconductor lasers operating in the red region of the spectrum (0.65–0.67 μm) were performed. It was revealed that for these lasers the dispersion parameter has a value of (0.13–1.40)·10−25 sec2/cm. It is shown that the dispersion of the active medium of a semiconductor laser with an external resonator can be compensated by inserting a quartz-glass rod into the resonator.

The lasingin an Nd:YAG laser with a fiber-optic reflector in the form of a loop was experimentally investigated. Two designs of the laser with a fiber-optic loop reflector were considered. In the laser of the first type the reflector was formed by a fragment of a fiber guide the ends of which were placed in the focal plane of a microscope objective. In the laser of the second type the role of the output mirror was played by a loop-shaped fiber-optic reflector made on the basis of a V-shaped fused three-fiber splitter. It is shown that when such lasers operate in the regime of free-running lasing, in them there takes place the effect of nonlinear conversion of the generated radiation frequency in the Stokes and anti-Stokes regions of the spectrum.

The possibility of using the Michelson microwave interferometer for the measurement of material permittivity in radiowave nondestructive testing is analyzed experimentally. It is shown that the use of the microwave interferometer permits fairly simply to determine the permittivity of thin-layer materials using a shift of one of the interferometer mirrors.

We report on collective effects for the train of optical pulses when a reproduction of the periodical pulse train occurs at some distance in dispersive medium. The reproduction of the initial temporal distribution can be treated as a temporal analog of the spatial Talbot effect. In experiment with a multimode fiber, the group of seven pulses lost its temporal shape converting in one broad pulse at the distance of 1200 m, while continuous train of pulse preserved its temporal structure.

Some nontrivial features of nonlinear transformation of frequency in the ring fiber resonator of free running YAG:Nd laser have been experimentally studied. Fiber of resonator has been matched with the laser active medium using microobjectives. Fibers of different lengths with the core diameters from 340 to 10 µm have been used. Nonlinear frequency transformation has been observed for fibers with core diameter of 60 pm and investigated lenths of resonator 43, 100 and 226 m. For all these fiber resonators in the antiStokes region spectral lines of 505, 532 and 558 nm have been presented. In the region of the Stokes component generation of the stimulated Raman scattering the row of narrow (with width less then 0.2 nm) spectral lines in the spectral region of 1127. . .1131 nm has been observed. The amount of the lines has been increased from 1 to 12 with increasing of the laser pumping power. In the anti-Stokes region for the long fibers (100 m and 226 m) the third harmonic of the main laser frequency additionally has been generated. Here it is also observed the two groups of lines in the spectral region of 1129 nm and 1137 nm, the amount of which depends from the pumping power of laser.In the same fibers under the excitation by the external YAG:Nd laser with the same power of radiation the spectral lines in the anti-Stokes region have not been observed and in the Stokes region the cascade generation of the stimulated Raman scattering has been taken place. The connection of the observed features with the spectral selective properties of the fiber ring resonator is discussed.

The polarization sensors on the singlemode optical fibers are investigated. The segment of the optical fiber clamped between two cylindrical or plane surfaces rotates the plane of polarization of the linear polarized light on the output of the fiber. The angle of rotation is proportional to the strength of clamping of the surfaces. This phenomenon can be used for the creation fiber-optical sensors of pressure or temperature.

An investigation was made of the characteristic features of the amplification (absorption) of modes in inhomogeneous optical waveguides with an adjacent active medium. The WKB approximation was used to derive equations for the calculation of the gain (absorption coefficient) of modes in waveguides with different refractive index profiles. It was found experimentally and theoretically that the gain (absorption coefficient) of modes in inhomogeneous waveguides could be made close to the gain (absorption coefficient) of the adjacent active medium.

An experimental study demonstrated that suitably aligned single-mode helium-neon lasers and also LG79 lasers operating in the nominal regime could be used as sources of stable periodic trains of subnanosecond pulses.