Process emission laser target of zinc selenide on the dielectric substrate with a circular shape and a hole diameter of 3 mm.
Staff at the Physics Institute. PN Lebedev Physical Institute (LPI) and the Institute of Electrophysics, Ural Branch of Russian Academy of Sciences (Ekaterinburg) have developed the design of a new type of laser — semiconductor electric discharge. With some approximation of the device can be called a perfect version of a streamer semiconductor laser.
An electric circuit semiconductor (PEL) Laser Power: 1 — transmission line 2 — Camera with electrodes 3 and 4, 5 — wafer laser target (LW) 6 — padded. LM is composed of a plane-parallel plate 5 and the semiconductor substrate 6 are connected by a thin dielectric layer 7 with one or more holes. PEL also contains a high-voltage pulse generator — not shown in the diagram
The term "electric-discharge laser" is better known in conjunction with the gas environment — were spread electric-gas lasers. Their work is, relatively speaking, is this: the voltage applied to the gas tube accelerates electrons, enhancing the ionization process, as a result there are conditions for the optical transitions, which give rise to, and then the generation of laser radiation. As for semiconductors, the famous "streamer" semiconductor lasers excited by nanosecond (10-7 — 10-8 s) pulses of high voltage. These lasers provide high pulse generator, one electrode of which is connected to the semiconductor wafer placed in a dielectric fluid, and the second removed a considerable distance in order to prevent the breakdown of the semiconductor wafer. A significant drawback of these lasers is the occurrence of lasing along certain crystallographic directions and the small diameter of the generating region (up to tens of microns), which is related to the distribution of electric fields in the crystal and limits the power increases the beam divergence and does not control the number and the location of a generating areas. Employees of LPI and the Institute of Electrophysics, Ural Branch of Russian Academy of Sciences were able to eliminate these shortcomings, which significantly changed the design of the laser and, in particular, used the picosecond pulses.
According to the head of development, Doctor of Technical Sciences Alexander Nasibova, thanks to the use of picosecond pulses is increased dielectric strength, can bring closer the electrodes between which the wafer and provide an environment in which the discharge is distributed in the direction of the electric field lines. This eliminates the need to place the crystal and the electrode in the liquid dielectric medium, there are additional opportunities semiconductor ionization radiation discharge and electron beam generated in the discharge gap by applying a high-voltage picosecond pulses. By picosecond pulses of electric field and the electron beam as a result of impact ionization and photoelectric tunnel a dense electron-hole plasma in which there are conditions for amplification and lasing.
After conventional semiconductor lasers based on pn junctions through which current is passed, and the resulting carrier injection is emitted. In the semiconductor electric discharge laser crystal is used, then there is no pn junction, running another principle that is more similar to what happens in gas lasers. "You applied voltage increases the electric field, the electrons are accelerated, is ionized atoms or ions, depending on which crystal and a plasma is formed in the crystal. And in the electron-hole plasma at a certain density of electron-hole pairs may be increased and the generation of light. That’s the idea we are implementing, "- said Alexander Nasibov.
Depending on the applied pulse voltage and the pulse duration (tens or hundreds of picoseconds) can emit laser light pulses of tens to hundreds of kilowatts with a wavelength determined by the band gap semiconductor — from 300 nm to 3 microns. The active element of the laser — wafer — may be made of double-or triple-direct-gap semiconductor compounds A2B6 (ZnS, ZnSe. CdS, CdSe, ZnSSe, ZnCdS, CdSSe) or A3B5 (GaAs. GaN, GaAlN, GaAlAs, AlN, InN, and so etc.).
Provided the use of the laser in optoelectronic devices, optical communication, the study of ultrafast processes in biological tissues and recording instruments.