C. J. Panchal

All-inorganic solid-state electrochromic devices: a review

Electrochromic devices (ECDs) are currently attracting much interest in academic and industry for both research and their commercial applications because of their controllable transmission, absorption, and/or reflectance. This paper reviews the progress that has taken place from 1969 until the year 2015 with regard to all-solid-state inorganic ECD fabrication. The main aim of this review article is to provide an easy entrance to literature of all-inorganic solid-state ECD.

Effect of facet reflectivities on high-power highly strained InGaAs quantum-well diode lasers operating at 1.2 μm

The power enhancement of laser diodes is achieved by single and multilayer facet coatings such as antireflection and high reflection respectively at the front facet and the back facet of the laser diode. In this work, we have experimented with single layer λ/4 thick Al2O3 film for the Anti Reflection (AR) coating and stack of λ/4 thick Al2O3/ λ/4 thick Si bi-layers for the High Reflection (HR) coating. The AR/HR coatings were deposited in an electron beam evaporation system. The effect of front and back facet reflectivities on the output power of diode laser has been studied. The highly strained MOVPE grown InGaAs quantum-well edge emitting broad area (BA) diode lasers have been used for this experiments. The light output versus current (L-I) measurements were made on selected devices before and after the coatings. The devices were tested under pulsed operation with a pulse width of 400 ns and a duty cycle of 1:400. We have also carried out the theoretical analysis and simulation of L-I characteristics for this particular diode structure using LabVIEW. The experimental results were compared with simulated results. The effect of facet coating on external differential efficiency of diode laser has also been studied.

In-situ reflectivity measurement for antireflection coating on laser diode facet

Many applications of Laser diode require antireflection coatings either on one or both the facets of the diode. These include, for example, semiconductor optical amplifiers, optical pumping for solid state lasers and creation of broad band source for tunable external cavity. We have used single layer antireflection coating on the front facet of the laser diode using electron beam evaporation technique to enhance optical power output from the facet. To optimize the coating conditions with precise control over facet reflectance of the laser diode, we have carried out experiment for In-Situ reflectivity measurement. We have used MgF2 as a low refractive index dielectric material for antireflection coating. The actual single layer AR coating consists of λ/4 thick MgF2 film. The reflectivity of the film being deposited is measured on GaAs test substrate, kept in close vicinity of the laser diode bar, with the help of a 657 nm (red) laser diode and a photo detector. A LabVIEW programme, called Virtual Instrument (VI), has been prepared to automate the whole experiment. We have also carried out simulation of facet reflectivity subject to the film thickness being deposited.

Structure, I-V characteristics and optical studies of delafossite CuFeO2 and CuFe0.96Ti0.03V0.01O2 prepared under high vacuum

Most opted methods for the preparation of CuFeO2 involve chemical route or solid state synthesis in the presence of inert gases like Argon and Nitrogen for the purpose of maintaining Cu in 1+ state. Here CuFeO2 (CFO) and doped CuFe0.96Ti0.03V0.01O2 (CFTO) samples are prepared under newly developed simple synthesis process involving high vacuum sealed annealing. Delafossite phase is confirmed by means of XRD measurements and its Rietveld refinement. The room temperature I-V measurements performed with different top contacts on the pallets show that CFO samples having ‘Ag’ and ‘In’ contacts shows better semiconducting properties compared to ‘Cu’ and ‘Al’ contacts owing to Schottky effect. On the other hand CFTO show good semiconducting nature only with ‘Ag’ contacts. Bulk samples of CFO exhibiting better semiconducting nature compared to CFTO is mainly due to electron doping (substitution of Ti4+ at the Fe3+ site) induced enhancement in recombination in a system having predominantly holes as carries. Effect...

Simple Low-Cost Technique for in-Situ Reflectivity Monitoring of Optical Thin-Films and its Application in Laser Diode Facets-Coating

Laser diodes are by far the most varied, flexible, cheapest and the most abundant lasers. For long-term, reliable operation and for maximum optical power utilization, laser diode is coated with the anti-reflection (AR) and high-reflection (HR) coatings by means of dielectric layers on the front and the back facet, respectively. For the optimum performance, accurate monitoring and control over the reflectivity of the dielectric thin film layers at specific lasing wavelength is necessary. We have demonstrated a simple and inexpensive in-situ reflectivity measurement system for the facets-coating of laser diodes. The system relies on the measurement of dynamic optical reflectance of the growing thin film by means of intensity of a laser-beam reflected from the gallium arsenide test-substrate kept in the close vicinity of the laser diode facet being coated. The in-situ reflectivity monitoring of single layer AR film and multilayer HR films have been demonstrated and verified with ex-situ reflectivity measurements.

Facet coating of diode laser for high-power and high-reliable operation

Multilayer coatings, such as Antireflection (AR) & High Reflection (HR), are used respectively in front & back facet coatings of diode laser for high power and long life operation. In this paper, we coated single layer AR coating using Al2O3MgF2 and multilayer HR coating using Al2O3 and MgF2 as a low refractive index layer and Si as high refractive index layer on GaAs substrates for optimization of coating conditions and HR coating using Al2O3\Si and MgF2\Si on diode laser chips. AR coating of diode laser is planned.