D. D. Shinde

Optical and local structural study of Gd doped ZrO2 thin films deposited by RF magnetron sputtering technique

ZrO2 samples with 0, 7, 9, 11, 13 % Gd doping have been prepared by RF magnetron sputtering deposition technique for solid oxide fuel cell application. The optical properties of the samples have been studied by transmission spectrophotometry and spectroscopic ellipsometry while the local structure surrounding Zr sites has been characterized by extended x-ray absorption fine structure (EXAFS) measurement at Zr K edge with synchrotron radiation. It has been observed that beyond 11% Gd doping, band gap decreases and refractive index increases significantly and also oxygen and Zr coordinations surrounding Zr sites increase which indicates the formation of Gd clustering in ZrO2 matrix beyond this doping concentration.

Refractive index tailoring of morphology engineered SiO2 thin films by collimated glancing angle RF magnetron sputtering

Conventional RF magnetron sputtering system was modified for collimated glancing angle deposition geometry at fixed vapour flux angle of 86° by employing a collimating plate designed and located parallel to the substrate. With this geometry, refractive index (RI) of morphologically engineered silica films ∼1.28 could be achieved against 1.48 @550 nm in conventional sputtered geometry along with the significant transmission (antireflection) of ∼93.7%, which makes this thin film suitable to be used in anti-reflection coatings for solar cell applications.

The effect of pulse width on asymmetric bipolar pulse DC sputtered tantalum pentoxide thin films

The effect of pulse width in asymmetric bipolar pulse DC (ABPDC) sputtering technique is studied by depositing a set of Ta2O5 dielectric thin films under varying pulse widths from 496-1616 ns. Structural studies showed no distinction among the deposited samples. Optical properties of the samples have been characterized by transmission spectrophotometry and spectroscopic ellipsometry which reveal that with increase in pulse width, the deposition rate and hence total thickness of the samples decreases while the percentage of substrate-film interface thickness increases. The void percentage in interface layers were found to be almost constant up to 1296 ns pulse width and increases substantially beyond this. The study is important from the point of pulse width optimization for depositing Ta2O5 thin films by ABPDC sputtering technique for optical multilayer thin film application.The effect of pulse width in asymmetric bipolar pulse DC (ABPDC) sputtering technique is studied by depositing a set of Ta2O5 dielectric thin films under varying pulse widths from 496-1616 ns. Structural studies showed no distinction among the deposited samples. Optical properties of the samples have been characterized by transmission spectrophotometry and spectroscopic ellipsometry which reveal that with increase in pulse width, the deposition rate and hence total thickness of the samples decreases while the percentage of substrate-film interface thickness increases. The void percentage in interface layers were found to be almost constant up to 1296 ns pulse width and increases substantially beyond this. The study is important from the point of pulse width optimization for depositing Ta2O5 thin films by ABPDC sputtering technique for optical multilayer thin film application.

Study of optical properties of asymmetric bipolar pulse DC magnetron sputtered Ta2O5 thin film as a function of oxygen content in deposition ambient

Tantalum penta-oxide thin films have been deposited by reactive sputtering technique using asymmetric bipolar pulsed DC source at various oxygen percentage viz. 0 to 50 %. The optical properties of the films have been studied by spectroscopic ellipsometry measurements. It has been observed that compact films with low void fraction, high refractive index and band gap can be obtained by the above technique with oxygen percentage in the range of 30–40%. The films deposited with zero or very low oxygen content have high deposition rate and yield metal rich films with large voids, defects, low band gap and high refractive index. Similarly films deposited with >40% oxygen content again contain voids and defects due to the presence of large amount of gas molecules in the sputtering ambient.

Fabrication of Quasicrystalline Microstructures using Moiré Fringe based Single Beam UV-Lithography

We report an innovative Moire patterning based lithographic method for fabricating photonic micro structures by using two wire meshes placed at desired angle with respect to each other resulting in 8 or higher fold rotational symmetry.

Noncontact three-dimensional quantitative profiling of fast aspheric lenses by optical coherence tomography

Abstract The use of optical coherence tomography (OCT) for noncontact three-dimensional aspheric lens profiling and retrieval of aspheric surface parameters is demonstrated. Two commercially available aspheric lenses with different focal length-to-diameter ratio have been imaged using OCT, and the measured optical path length distribution has been least square fitted with the aspheric lens surface retrieving the radius of curvature, aspheric constant, and conic constants. The refractive index of these lenses has also been measured referencing with a standard Zerodur glass flat. The fitted aspheric surface coefficients of the lenses are in close agreement with the manufacturer’s values, thus, envisaging the potential of OCT in rapid screening, testing of aspheric lenses, and other micro-optical components such as those used in illumination optics.

Comparison of spectral performance of HfO2/SiO2 and TiO2/SiO2 based high reflecting mirrors

High Reflecting (HR) mirrors of two different material combinations viz., HfO2/SiO2 and TiO2/SiO2 have been fabricated by asymmetric bipolar pulse DC magnetron sputtering technique. The spectral performances of both the mirrors have been tested in the visible range. Multilayer mirror consisting of TiO2/SiO2 combination shows better spectral performance, viz., 7.2 % higher peak reflectance and 119 nm larger spectral bandwidth, as compared to that of HfO2/SiO2 combination. The reason is attributed to the higher contrast in index in the first case.