Ashok Chauhan

Realization of Long-Period Corrugated Grating in Silica-on-Silicon-Based Channel Waveguide

Long-period corrugated grating in silica-on-silicon-based channel waveguide is realized by making periodic corrugation on top of a relatively high-indexed (contrast ap.8%) Ge-doped silica waveguide, which is sandwiched between undoped silica undercladding and boro-phospho-silicate-glass overcladding layers. Resonance wavelength of the 15-mm-long grating is found at ~1581 nm, having negligible polarization dependency at room temperature, with a grating strength of ~11 dB and 3-dB bandwidth of 7 nm. The temperature characteristic of the grating is also investigated, which is found to be similar to that of the long-period fiber grating. This device has significant potential for various integrated-optic communication and sensing applications.

A Top-Down Approach for Fabrication of Nanorods on GaN-Based LEDs Using Self-Assembled Ni

In optoelectronic devices such as LEDs, LASERs, strain-induced piezoelectric polarization occurs in the structure because of large lattice mismatch occurs between sapphire substrate and GaN layers. This degrades the performance of these devices due to strain-induced piezoelectric polarization. Nanostructuring can reduce this stress due to reduction in quantum-confined stark effect (QCSE) and strain-releasing effect. We demonstrate a top-down approach for fabricating GaN nanorods on LED using self-assembled nickel as an etching mask during reactive ion etching (RIE). The self-assembled Ni islands were formed by rapid thermal annealing at 850 °C for 1 min followed by RIE. The shape and morphology of GaN nanorods were studied using scanning electron microscopy (SEM). We realized vertical array of nanorods with dimensions varying from 90–200 nm.

Top- and Bottom-Patterned GaN/InGaN Violet Light Emitting Diode Structure for Enhanced Light Extraction

Micro-patterning is carried out on top-surface of GaN/InGaN violet LEDs grown on patterned sapphire substrates (PSS). Electro-luminescence/ light-output of hexagonal hole-type and grating-type LEDs are found 1.8/2.0 and 1.4/1.5 times higher compared to conventional LED respectively.

Fabrication and characterization of InGaN/GaN MQWs blue light-emitting diodes on sapphire substrate

In this paper, we report successful fabrication and characterization of InGaN/GaN MQWs based blue LEDs on c-plane sapphire substrate. The epitaxial material used in the fabrication of blue LEDs was grown by metal-organic-chemical vapor deposition (MOCVD) system. The threshold voltage (Vth) of fabricated InGaN/GaN MQWs blue LED on c-plane sapphire substrate was ~ 3.1 V.

Corrections to “Realization of Long-Period Corrugated Grating in Silica-on-Silicon-Based Channel Waveguide” [15 Oct 09 1490-1492]

In the above titled paper (ibid., vol. 21, no. 20, pp. 1490-1492, 15 Oct. 09), the first sentence of the Conclusion contained the following error: a length of 15 nm should read a length of 15 mm.