Ravi Kant Choubey

Mach-Zehnder interferometric photonic crystal fiber for low acoustic frequency detections

Low frequency under-water acoustic signal detections are challenging, especially for marine applications. A Mach-Zehnder interferometric hydrophone is demonstrated using polarization-maintaining photonic-crystal-fiber (PM-PCF), spliced between two single-mode-fibers, operated at 1550 nm source. These data are compared with standard hydrophone, single-mode and multimode fiber. The PM-PCF sensor shows the highest response with a power shift (2.32 dBm) and a wavelength shift (392.8 pm) at 200 Hz. High birefringence values and the effect of the imparted acoustic pressure on this fiber, introducing the difference between the fast and slow axis changes, owing to the phase change in the propagation waves, demonstrate the strain-optic properties of the sensor.

Development of Humidity Sensor Using Nanoporous Polycarbonate Membranes

In the present work, the effect of temperature and moisture has been studied on nano-porous polycarbonate membranes of size 15, 50, and 80 nm, respectively to formulate the calibration curves for the future development of humidity sensors. These studies were conducted for virgin as well as humid samples while the temperature range was kept from room temperature to 160°C. Interesting variations in the capacitance with pore size and temperature have been observed. Calibration curves demonstrate that nanoporous polycarbonate samples are one of the important candidates for developing humidity sensors. In addition surface behavior has also been studied for the selective samples to better understand the dielectric behavior for nascent as well as moisturized samples.

Effect of Copper Doping on Physical Properties of Cadmium Oxide Thin Films

Nanostructured materials have generated considerable interest owing to their physical and chemical properties that differ from those of their bulk counterparts. Cadmium oxide (CdO) is an important semiconducting material with varying band gap from 2.2 to 2.9 eV used for various applications. Due to its high electrical conductivity and optical transmittance in the visible region, this material is having potential application in photovoltaic devices as well. This study focuses on the preparation and characterization of CdO (undoped and 2 % Cu-doped) produced by facile sol–gel spin coating. Effect of Cu doping on the structural, optical and morphological properties of CdO have been studied.

Synthesis, Structural and Optical Properties of Transition Metal Doped ZnO Nanoparticles

Metal oxide Ni doped ZnO nanoparticles were synthesized through microwave method. Structural studies were carried out using XRD, and FTIR spectroscopy. XRD results clearly show the formation of all samples in single phase without any impurity and the average crystallite size has been observed to vary between 20.10 and 14.38 nm. Band at 380 cm−1 observed in FTIR spectrum is attributed to the Zn–O stretching confirms the formation of ZnO nanoparticles.

Effect of ferromagnetic dopants on laser induced optical parameters of bismuth doped CaS phosphors

The effect of ferromagnetic impurities (Fe, Co, and Ni) on the laser induced optical parameters of CaS:Bi phosphors has been studied. The studies were done for the Bismuth concentration of 0.4% in CaS phosphors due to the highest value of oscillator strength as reported earlier. The studies were conducted using nitrogen laser as a excitation source in a pulse excitation mode at room temperature. Appreciable changes in the optical properties have been detected after the addition of ferromagnetic impurities in the CaS phosphor doped with bismuth. The nature of the multiple exponential decays remains the same even after the addition of ferromagnetic impurities in the present case of bismuth-doped phosphors which is in agreement with the earlier work reported on other dopants in sulfide type phosphors. As ferromagnetic impurities enhanced the optical parameters of CaS phosphors appreciably, these studies shows that they can be used to control the transition probability and the corresponding optical parameters.

Degree of supersaturation: An effective tool to control the luminescence efficiency and size distribution in CdTe quantum dots

Supersaturation controlled synthesis of thioglycollic acid (TGA) capped CdTe quantum dots in aqueous medium has been carried out. With a four-fold increase in the degree of supersaturation, the photoluminescence quantum efficiency of the nanoparticles was enhanced more than five times to a remarkably high value of 46%. This was accompanied by concomitant narrowing of the size distribution of the QDs. The simplified approach obviates the need for post-preparative treatments to improve the particle characteristics.