Satchi Kumari

Ultraviolet and blue photoluminescence from sputter deposited Ge nanocrystals embedded in SiO2 matrix

Ge nanocrystals (NCs) embedded in silicon dioxide (SiO2) matrix are grown by radio-frequency magnetron sputtering and studied in order to understand the origin of ultraviolet (UV) and blue photoluminescence (PL) from the NC-SiO2 system. Ge NCs of diameter 7–8 nm are formed after postdeposition annealing, as confirmed by transmission electron microscopy and Raman scattering studies. Optical Raman studies indicate the presence of strain in the embedded Ge NCs. Polarization dependent low frequency Raman studies reveal surface symmetrical and surface quadrupolar acoustic phonon modes of Ge NCs. PL studies with 488 nm excitation shows a broad emission band peaked at ∼545 nm, which is attributed to oxygen deficient defects in the SiO2 matrix. PL studies with 325 nm excitation show additional strong peaks in the 377–400 nm region. Time resolved PL studies in the UV-blue range show double exponential decay dynamics in the nanosecond time scale, irrespective of the NC size. Comparative studies of PL emission from ...

Effect of Pump Intensity on Slowing Down of Light in

The slowing down of light in Ce:BaTiO3 at room temperature via degenerate two-wave mixing for chopped pulses is reported. Delay of 0.9 ms is observed for chopped pulses of duration 8 ms, corresponding to a group velocity of 5.5 m/s. Effect of pulse width of signal beam and pump intensity onto the slowing down action of light in the crystal is studied. The building up and decay time of photo grating is also recorded as a function of pump beam intensity.

{\rm Ce{:}BaTiO}_{3}

Deposition of optical quality C-axis oriented epitaxial thin film of ruby via pulsed laser deposition technique on sapphire substrate is reported. The film is characterized by Raman spectra and photoluminescence spectra. The peak positions of R-line and the corresponding linewidth are observed to be temperature dependent. The sensitivity of R(1)-line position, υ, with the temperature, (dυ/dT), in the range of 138-368 K shows linear behavior confirming its applicability as temperature sensor.

Crystal via Degenerate Two-Wave Mixing Using Chopped Pulses

The propagation of flat top pulse is studied inside the crystal via degenerate two-wave mixing as a function of various polarization states of a pump-probe beam. Subluminal as well as superluminal pulse propagation is observed by tuning the crystal orientation for S-S and P-S polarization states of a pump-probe laser beam.

Note: epitaxial ruby thin film based photonic sensor for temperature measurement.

Nanocrystalline zinc oxide-thin films have drawn the attention of researchers due to its attractive properties like transparency in visible region, abundance in nature and gas sensitivity. Nanostructured Zinc oxide (ZnO) thin films were grown on silicon, alumina and glass substrates at various substrate temperatures using a 6 kW electron beam evaporation technique. The effects of film thickness, growth temperature and substrate on the crystallinity of deposited ZnO films were investigated using X‐ray diffraction, scanning electron microscopy, optical absorption and photoluminescence studies. Our studies show that good quality films are obtained for silicon substrate for a growth temperature of 250°C. Film thickness plays an important role on the evolution of the nanostructures. SEM studies combined with XRD analysis reveal that ultrathin nanorods are grown with (002), (101) and (102) orientations. All the ZnO films show room temperature photoluminescence emission bands at 394 nm and 468 nm. Optical absorption studies show strong absorption at 377 nm. Details of the structure and optical properties correlation will be presented and potential of a simple technique such as e‐beam deposition to grown ZnO nanostructures suitable for optoelectronic application will be assessed.

Effect of Pump-Probe Polarization and Crystal Orientation on Propagation of Flat Top Pulse in

Epitaxial ruby thin film is deposited via pulsed laser deposition technique. The charateristic R-lines in PL spectra confirmed ruby phase in the film. Raman spectra showed C-axis growth of the film. The nonlinear absorption coefficient and nonlinear refractive index of film were found to be β ~ 5.2 × 10^-5 m/W and n₂ ~ 3.1 × 10^-5 m²/W, respectively. Further, the sub as well as superluminal propagation of 130-ns Gaussian pulse in 3.5-μm-thick PLD ruby thin film is reported in this paper. A delay of 17 ns is observed at film orientation of +45°, whereas pulse advancement of 12 ns is observed at -45°. Pulse broadening and compression are also observed with film rotation.