Dislocation-related conductivity in Au(In)/Cd1–xZnxTe(x = 0, 0.1) Schottky contacts

Dislocation-related conductivity is studied in Schottky contacts Au(In)/Cd1-xZnxTe (x = 0, 0.1) prepared on the surface of single crystals modified by multiple irradiation with a ruby laser and mechanical polishing. The contacts were examined by measuring the DC current as a function of the applied bias and temperature as well as the photoelectric response. It is shown that both methods of surface modification result in p-to-n conversion of the conductivity type of the surface layer. The charge transfer in contacts is explained by the formation of dislocation networks buried under the surface. A model of two potential barriers is proposed for the interpretation of the photovoltaic response in contacts. Their existence is associated with compressive strains in the modified surface layer caused by dislocations, which leads to an increase in the band gap and the formation of a heterostructure.

Liquid crystal lasers: the last decade and the future

The demonstration of the first ruby laser in 1960 led to a revolution in science and technology. The lasers have significantly influenced the development of new approaches to spectroscopy, giving previously undreamed insights into physics, chemistry, and other scientific areas. The search for new materials for light amplification is one of the fundamental subjects of modern photonics and nanotechnology. In this review, we summarize the most appealing progress in developing liquid crystalline (LC) micro and nano-lasers during the last decade, together with their applications and description of perspectives for the future. We will describe the physical background necessary to understand the operation principles of LC lasers, including a description of radiative transition phenomena and LC matter. The article will be divided into separate sections concerning different approaches of LC lasers realization, including; band edge, DFB, DBR, VECSEL, and random cavities utilization. We will also discuss how the LC phases can influence the design of laser devices. Finally, the potential applications, perspectives, and conclusions will be discussed at the end of the article.

A Simulation Based Study for the Early Detection of Glaucoma Using Temperature Profiling of Human Eye

Glaucoma is one of the leading ophthalmologic disorders worldwide which results in irreversible blindness if left untreated. Although many detection techniques are already in use, they prove to detect glaucoma at a later stage when the disease causes irreversible effects to the optic tissue. This work aims at developing a novel technique to detect the presence and progression of glaucoma at an early stage through temperature profiling of optic tissues by LASER radiation. A 3D CAD model of the real human eye designed in SolidWorksTM was used and different parameter values were defined for performing thermal simulation in COMSOL Multiphysics® for three distinct LASER point sources: 694.3 nm Ruby LASER, 1064 nm Nd:YAG LASER and 1340 nm Nd:YAP LASER. By analyzing the thermal profile obtained from the simulation, an inverse trend of temperature variation with progression of glaucoma was observed. The effect was most prominently observed in using 694.3mm Ruby LASER with no such temperature rise in the eye causing any physiological harm. This work shows the possibility of using temperature profile due to irradiated light on human eye as a novel biomarker for the early detection of glaucoma. Dhaka Univ. J. Sci. 68(1): 37-44, 2020 (January)

Наносекундное воздействие интенсивного лазерного излучения на тонкие плёнки TiAlN

The spectral dependencies (λ = 0.35-1.0 μm) of the transmittance and reflectivity (R) of TiAlN thin films deposited on glass and Si substrates by magnetron sputtering technique have been measured. The TiAlN/Si films of 0.5 μm thickness were irradiated by single nanosecond (70 ns) ruby laser pulses in order to study the influence of laser-induced thermophysical processes in TiAlN on its R(t) dynamics at the wavelengths λ1 = 0.53 and λ2 = 1.06 μm of probing radiation, and on the state of laser irradiation zones, which was studied by optical and scanning electron microscopy. The observed in the experiment and connected with the pulsed heating dynamics changes of R - increase at λ1 and decrease at λ2 amplifies as the irradiation energy density W approaches to the threshold of laser ablation of the nitride ~ 1 J/cm2. Laser-induced thermophysical processes, occurring at W = 0.6-0.9 J/cm2, lead to a specific modification of the TiAlN layer with the formation of a net of cracks due to thermal stresses arising during the laser pulse. The increase of W leads to the formation of a more developed net/cellular structure of the film with a smaller average size of cells.