Laser fabrication of functional micro-supercapacitors

The purpose of the present chapter is to give an introduction into the physics of laser plasma interactions that govern the coupling of laser energy into the matter. Processes induced by laser pulses of nano- and femtosecond durations are discussed in the framework of different applications. In particular, the roles of non-linear absorption and avalanche ionization in plasma heating are discussed and a critical review of related experimental and theoretical studies is given.

Laser–Plasma Interactions

This paper summarizes the peculiarities of the nonlinear interaction of laser pulses with the noncrystalline semiconductors (chalcogenide glasses (ChG), a-Si:H), showing that noncrystalline semiconductors (NS) are an interesting material for high-speed optoelectronics. The physical mechanisms which can contribute to the nonlinear light absorption in NS under pulsed excitation are critically reviewed. The results of photo-induced absorption (PA) measurements in ChG are examined and a model taking into account the multiple trapping of carriers on localized states is proposed as an explanation.

https://iopscience.iop.org/article/10.1088/0963-9659/7/2/025/pdf

Nonlinear optical phenomena in chalcogenide glasses

http://iopscience.iop.org/article/10.3367/UFNe.2017.01.038047/pdf

Electrohydrodynamic flow for the active control of gas flows

An investigation is made of the characteristics of the formation of a self-controlled volume discharge for pumping CO2 lasers, i.e., self-sustained volume discharge (SSVD), which involves the preliminary filling of a discharge gap by an electron flux from an auxiliary discharge plasma. It is determined that this method is suitable for large interelectrode gaps, that distortion of the electric field in the gap by the space charge of the electron flux plays an important role in the formation of the discharge, that the electrodes could be profiled dynamically during propagation of an electron flux through the discharge gap, and a SSVD could form in systems with a strongly inhomogeneous field. High-power SSVD-based CO 2 laser systems are created and investigated. Another type of self-controlled volume discharge without preionization, i.e., a self-initiated volume discharge (SIVD), in nonchain HF lasers with SF 6 –C 2 H 6 mixtures is also investigated. It is established that, after the primary local electrical breakdown of the discharge gap, the SIVD spreads along the gap in directions perpendicular to that of the electric field by means of the successive formation of overlapping diffuse channels under a discharge voltage close to its quasi-steady-state value. As new channels appear, the current that flows through the channels formed earlier decreases. The volume occupied by the SIVD increases when the energy deposited in the plasma increases, and, when the discharge volume is confined by a dielectric surface, the discharge voltage increases simultaneously when the current increases. The possible mechanisms that explain the observed phenomena, namely the dissociation and electron attachment of SF 6 molecules, are examined. A simple analytical model is developed that makes it possible to describe these mechanisms at a qualitative level. High-power SIVD-based HF(DF) lasers are developed and tested.

High-power self-controlled volume-discharge-based molecular lasers

Optimization of the pumping regime and of the resonator parameters, as well as the correct choice of easily ionizable additives to the active mixture of a CO2 laser excited by an SSVD ensured a specific output energy of 51 J/l and a conversion efficiency of electrical into optical energy of 22 % in an active medium volume of 16 l.

High-Energy Electric-Discharge CO 2 Laser with Easily Ionizable Substances Added to the Mixture

An experimental investigation was made of the interaction between pulsed CO2 laser radiation and the optical breakdown plasma generated by this radiation near the surfaces of glass, Duralumin, quartz, polymethylmethacrylate, and lithium fluoride samples. This radiation had durations of 2 and 10 μs and an energy density of between 1 and 40 J/cm2 in a radiation spot of 3 cm2 area. The plasma shielding of the laser radiation had a threshold at energy densities exceeding appreciably the energy threshold of plasma formation. In the range of laser pulse energies between these two thresholds the plasma remained transmitting for the laser radiation. The shielding energy thresholds were determined and it was found that the fraction of the laser pulse energy not transmitted by the plasma reached saturation at the 0.5–0.9 level, depending on the materials studied.

I. S. Tsenina

Papers

High-Energy Electric-Discharge CO 2 Laser with Easily Ionizable Substances Added to the Mixture

Growth of shielding in a laser plasma