V. M. Kotov

Metal-semiconductor-metal photodiodes based on ZnCdS/GaP wide-gap heterostructures

Good epitaxial ZnCdS layers are grown on GaP semiconductor substrates by metal-organic chemical vapor deposition. The respective photodiode structures are fabricated by the metal-semiconductor-metal method, and their characteristics are studied. The diodes feature low dark currents. The bias dependence of the spectral response of the detector is determined. The long-wavelength edge of the ZnCdS/GaP diodes shifts from 355 to 440 nm as the bias voltage varies from 40 to 80 V. At the maximal photosensitivity wavelength (355 nm), the ampere/watt sensitivity of the detector is 0.1 A/W.

MSM optical detector on the basis of II-type ZnSe/ZnTe superlattice

On the basis of a type-II ZnSe/ZnTe superlattice, a MSM (metal—semiconductor–metal) photodetector is fabricated and investigated. The detector features low dark currents and a high sensitivity. The spectral characteristic of the detector provides the possibility of the selective detection of three separate spectral portions of visible and near-infrared radiation.

TeO2 single-crystal acoustooptic 2×2 switch for light beams of different wavelengths

The principles of acoustooptic switching of two light beams of different wavelengths by means of an acoustooptic interaction with two acoustic waves are examined. A version in which the acoustic waves form parallelograms and a version with strictly orthogonal propagation are considered. The latter version is the more attractive one when a TeO2 single crystal is used as the acoustooptic cell. Experiments on the switching of two-color Ar laser radiation with wavelengths λ1=0.5145 and λ2=0.488 µm are carried out and demonstrate a high switching efficiency. On the whole, the experiment confirms the basic conclusions of the theory.

Selective UV radiation detection on the basis of low-dimensional ZnCdS/ZnMgS/GaP and ZnCdS/ZnS/GaP heterostructures

The detecting properties of periodic heterostructures with ZnCdS quantum wells separated by ZnMgS or ZnS barrier layers are studied. Heterostructures are grown on semi-insulating GaP substrates by metal organic vapor-phase epitaxy (MOVPE). On their basis, metal–semiconductor–metal (MSM) diodes with interdigital Schottky contacts 3 μm, distances between them of 3 μm, and a total detector area of 100 × 100 μm are fabricated. The detectors have low dark currents (10–12 A); at low bias voltages, they provide a narrow- band response (full-width at half-maximum of FWHM = 18 nm at a wavelength of 350 nm) which is controlled by the ZnCdS quantum-well composition. As bias is increased to 70 V, the maximum detector sensitivity shifts by a wavelength of 450 nm, which is caused by penetration of the external-bias electric field into the semi-insulating GaP substrate. In this case, the narrow-band response of the detector at a wavelength of 350 nm is retained, i.e., the two-color detection of light is provided.

Collinear interaction of bichromatic radiation with one acoustic wave in biaxial crystals

The regime of collinear interaction of bichromatic optical radiation in biaxial crystals is considered. It is shown that the possibility of the realization of such an interaction is due to dispersion of the optical axes in a biaxial crystal.

Acoustooptic 2×2 switch for radiation with different wavelengths as an element of a fiber-optic gyroscope

Planar acoustooptic 2×2 directional couplers that switch optical rays with different wavelengths are considered. A method for calculating the angular and frequency characteristics of such switches is developed, and the parameters of a switch based on a planar Ti-LiNbO3 structure are calculated. Experiments employing bulk acoustooptic diffraction in TeO2 are performed, confirming the basic theoretical assumptions. It is shown experimentally that the best conditions for switching optical rays directed into optical fibers can be provided nearly always by varying the diffraction angles and the frequencies of the sound waves. The functional possibilities of the 2×2 directional coupler investigated in a fiber-optic gyroscope are described.