A S Nasibov

A setup for recording the picosecond dynamics of radiation of semiconductor targets in a gas diode

On the basis of a РАДАН generator of high-voltage subnanosecond pulses, an experimental setup for recording the picosecond dynamics of excitation of optical radiation in semiconductor targets (plates) in strong electric fields has been developed. Semiconductor targets were placed between the electrodes to which voltage pulses with an amplitude of up to 150 kV were applied. These pulses were delayed by a coaxial transmission line by 20–30 ns. This technique allowed realization of triggering in advance the sweep of an electron-optical camera and studying of the dynamics of emission from targets with a resolution of 5 ps at a synchronization accuracy close to the rise time of an acting high-voltage pulse.

Diagnostics of Radiative Processes in Semiconductors, Excited by Ultrashort High-Voltage Pulses

A configuration of the multichannel system for diagnostics of radiative processes in various regions of the discharge appearing in semiconductors in response to high-voltage pulses is considered. The system allows real-time recording of spectra, dynamics, and energy of radiation in nine emitting object zones 200–400 μm in diameter. The recording equipment is connected to objects under study by fiber-optic cables (FOCs). The system temporal resolution can be varied from 40 to 250 ps depending on the FOC diameter. An example of the simultaneous study of spatiotemporal characteristics of the streamer discharge at seven points of a CdSxSe1−x semiconductor wafer is given.

Excitation of high-intensity laser radiation of semiconductor targets by a subnanosecond electron beam

The results of the excitation of СdS semiconductor targets by a subnanosecond electron beam (EB) with an electron energy of 60–230 keV are presented. The maximum intensity of laser radiation from targets for a 1-mm EB diameter exceeded 107 W/cm2 at an efficiency of ~10%. Lasing was initiated at the leading edge of the EB current; laser radiation then reproduced the shape of the excitation pulse. At low excitation levels, a single-mode lasing regime with the wavelength λ = 522 nm was observed. The maximum power of laser radiation (10 MW) was achieved on a multielement CdS semiconductor target. The duration of laser pulses changed in the range of 100–500 ps.

Laser emission efficiency of semiconductor target of gas diode in the picosecond range

Laser radiation excited in a cadmiumsulfide semiconductor target (ST) (λ = 522 nm) by a high-intensity subnanosecond electron beam (EB) with an energy of 70–150 keV has a maximum intensity of 3 · 107W/cm2 at an efficiency of~10%. Lasing arose at the EB exciting pulse front. The laser radiation pulse shape reproduced the EB pulse shape.

Laser radiation of CdS{sub x}Se{sub 1-x} targets in a gas diode

Laser radiation of semiconductor targets of CdSxSe1-x solid solutions excited by an electron beam in a gas-filled diode was investigated at constant and varying gas pressures. In the first case, lasing was excited by an electron beam with an energy of 170 keV and a duration of 100 ps in semiconductor targets with different x. The highest powers 125 and 96 kW were achieved at x ≈ 0.2 (λ ≈ 677 nm) and x ≈ 1 (λ ≈ 522 nm), respectively. The minimum power (26 kW) was observed in the yellow-green spectral region. The maximum slope efficiency in these experiments reached 9%. In the second case, the radiation power of CdS targets (x = 1) was studied as a function of the air pressure in the gas diode varying from 0.1 to 2.5 Torr. The experimental data well agree with the calculation results. The possibility of reducing the radiation divergence by using a conical optical fibre is demonstrated. At the lasing threshold of semiconductor targets exited by an electron beam or a streamer discharge, filamentary channels appear due to, probably, an anisotropy of the impact ionisation coefficient.

A2B6 electric-discharge semiconductor focon laser

The working principle of the electric-discharge semiconductor focon laser is considered. CdS, CdxZn1−xSe, and CdSxSe1−x plates were used as active medium. In the case of CdS, lasing at λ = 525 nm was observed. The radiation power reached 3 kW, the pulse duration being 3 ns. The conditions of generation initiation in the streamer regime are considered. The spectral characteristics of discharge channel radiation in CdxZn1−xSe and CdSxSe1−x plates are investigated. The spectrum is shown to consist of discrete lines occurring upon discharge propagation and corresponding to the change in the composition of the ternary compound obtained in the course of single crystal growth. The application of ternary solid solutions A2B6 is supposed to help in obtaining a successive laser pulse generation within the range of 480 to 700 nm.

Laser radiation of CdxZn1−xS semiconductor targets of the gas diode

The experimental results on the study of radiation of CdxZn1−xS semiconductor targets (STs) of the gas diode (GD) for the pressure variation from 10−1 Torr to the atmospheric pressure are presented. Pulses 0.5–1 ns long with an amplitude to 200 kV were applied to the GD cathode. Laser radiation (509 nm) was generated in the ST under a beam of accelerated runaway electrons to a pressure of 2.5 Torr. At atmospheric pressure, generation in the ST was observed in discharge channels when the streamer moved from one ST surface to another. In this case, as the electric fields strength increased, radiation sequentially arose at three spectral lines, 509, 480, and 469 nm. Possible causes of the observed phenomena are considered.

Generator of picosecond laser pulses

The design of the generator of picosecond laser pulses and the results on semiconductor target (ZnSe, CdS, and others) excitation by electric field and electron beam pulses are presented. The maximum power of laser radiation reached 10 kW at pulse durations of 100–200 ps.

An experimental setup for exciting semiconductors and dielectrics with picosecond electron-beam and electric-field pulses

An experimental facility for forming high-voltage pulses with amplitudes of 30–250 kV and durations of 100–500 ps and electron beams with a current density of up to 1000 A/cm2 is described. The facility was built using the principle of energy compression of a pulse from a nanosecond high-voltage generator accompanied by the subsequent pulse sharpening and cutting. The setup is equipped with two test coaxial chambers for exciting radiation in semiconductor crystals by an electron beam or an electric field in air at atmospheric pressure and T = 300 K. Generation of laser radiation in the visible range under field and electron pumping was attained in ZnSSe, ZnSe, ZnCdS, and CdS (462, 480, 515, and 525 nm, respectively). Under the exposure to an electric field (up to 106 V cm−1), the lasing region was as large as 300–500μm. The radiation divergence was within 5°. The maximum integral radiation power (6 kW at λ = 480 nm) was obtained under field pumping of a zinc selenide sample with a single dielectric mirror.

Superluminescent room-temperature Fe{sup 2+}:ZnSe IR radiation source

The superluminescence of a Fe2+:ZnSe crystal was obtained in the region from 4.6 to 4.7 μm upon transverse pumping by high-power laser radiation at 2.94 μm. The superluminescence pulse energy was ~1 mJ upon pumping by a 15-mJ pulse. A ZnSe crystal was doped with Fe2+ ions by the diffusion method under the conditions of the thermodynamic equilibrium of phases.