Babu Ram Singh

Analysis and Design of Corrugated Long-Period Gratings in Silica-on-Silicon Planar Waveguides

A detailed theoretical analysis on light transmission through a corrugated long-period waveguide grating made in a silica-on-silicon planar waveguide is presented. A grating period of ~280 mum is considered in order to achieve a strong rejection band at a wavelength region of 1.5 mum. Phase-matching graphs are studied to find the relationship between the resonance wavelength and the grating period. The effects of the variation of the waveguide and grating parameters on the resonance wavelength are investigated in detail. Polarization dependence on the waveguide gratings is studied, and finally, the design is optimized by proper choice of the grating parameters, which results in a polarization-independent rejection band in the operating wavelength region. This type of waveguide grating has significant potential for various integrated-optic devices and sensing applications.

Electrochemically Fabricated High‐Barrier Schottky Contacts on n‐InP and Their Application for Metal‐Semiconductor‐Metal Photodetectors

The results of a study of electrochemically fabricated Pt/n-InP Schottky contacts and the feasibility of the process for InP-based metal-semiconductor-metal photodetectors are reported in the present paper. The electrochemical process yields a significant improvement of Schottky-barrier properties. This is mainly attributed to two advantages of the process: first, the in situ etching of the semiconductor surface just prior to Schottky contact formation and second, the damage-free metallization. The ideality factor and barrier height obtained for the Pt/n-InP Schottky contacts are 1.03 and 0.65 eV, respectively. A damage-free Pt/InP interface is revealed by the deep-level transient spectroscopy spectrum. The X-ray photoelectron spectroscopy sputter-profile of the electrochemically fabricated Pt/InP is presented. The metal-semiconductor-metal photodetector structures of an active area of n-InP, 100 x 100 {micro}m fabricated by the same process, show a dark current of 10 nA and a capacitance of 0.65 pF at a 5 V bias.

Improved Design of 8-Channel Silicon-on-Insulator (SOI) Arrayed Waveguide Grating (AWG) Multiplexer Using Tapered Entry into the Slab Waveguides

An improved design of silicon-on-insulator based 8 × 8 AWG multiplexer is presented using tapered entry into the slab waveguide. Our simulation result clearly shows significant enhancement of electric field from 0.44 V/m to 0.732 V/m, reduction in insertion loss from 7.13 db to 2.7 db, with bandwidth of 230 GHz and channel spacing 200 GHz while keeping other parameters within acceptable limits.

Effect of oxygen plasma on the electrical characteristics of GaAs MESFETs

Abstract Plasma induced damage often degrades the electrical and optical performance of the compound semiconductor based microwave/photonics devices and circuits. We have investigated the effect of oxygen plasma on the performance degradation of GaAs MESFETs, as measured by changes in breakdown voltage, saturation current, channel resistance, drift mobility etc. The performance degradation of the device is attributed to reduction of carrier mobility in the material due to ion bombardment.

Deep reactive ion etching of silica for planar lightwave circuits using indigenously developed ECR/RIE system

Deep dry etching of silica is used for patterning of waveguides for optoelectronic applications. We report on the use of Electron Cyclotron Resonance/Reactive Ion Etching process for deep reactive ion etching of silica glass films using different fluorocarbons as etch gases. 1 by 8 splitter has been used as test structure for the optimization of the etch process. The optimized process parameters like RF/Microwave power, pressure and gas composition etc. for the above have been presented.

622 Mbps APD/FET optical front-end receiver: Design, technology and performance

APD/FET optical receivers are preferred choice over PIN/FET for high data rate, high sensitivity applications mainly because of APDs combine detection of optical signal with internal amplification of photo current. However, there are number of critical issues such as device and preamplifier design, circuitary required to keep the Avalanche photodetector (APD) biased at optimum gain and temperature compensation of bias being applied to it etc., have to be addressed to realize an optical receiver with desired performance. This paper deals with the design and fabrication of 622 Mbps optical receiver front-end using Separate Absorption Graded Multiplication (SAGM) APD for photodetection and combination of MESFET and BJT for transimpedance amplifier design. AIMSPICE has been extensively used to simulate appropriate biasing of the active and passive devices taking into account various parasitics like miller capacitances, lead inductance etc. in order to optimize DC and AC performance of the circuit. Cr/Cu/Au thin film technology and solderable surface mount devices (SMD) have been used for its fabrication. Also included are the optical receiver performance in terms of Sensitivity and Dynamic range.

High Power 980-nm in GaAs/AlGaAs Strained Quantum Well Lasers for Pumping Applications

The present paper deals with the material and device design, technology and recent results on the performance of 980 nm laser diodes developed at CEERI. The issues related to material structure, device design and optimised process parameters are discussed. Typical L-I characteristics of these devices and important device parameters such as threshold current, emission wavelength and slope efficiency are included and discussed.

GaAs MMIC Based Fiber Optic Analog CATV Receiver: Design, Technology and Performance

The design, development and technological aspects of a fiber optic analog CATV receiver have been discussed vis-a-vis its conventional Silicon Hybrid counterpart. This provides an economical solution for the deployment of fiber optics in the trunk and feeder segments of the fiber based networks with superior characteristics and ease of compatibility with advanced multiplexed lightwave CATV and other futuristic systems based on digital transmission techniques.

Three-stage monolithic optical preamplifier on GaAs substrate

Abstract A three-stage GaAs monolithic transimpedance preamplifier for 155 Mbps data-rate optical receiver has been designed, fabricated and tested . Mesa/epitaxial technology of 1 μm gate length D-MESFET is employed for its implementation. The feedback resistor is realized using GaAs epitaxial layer. The buffered FET logic (BFL) approach is followed for the amplifier design. A close correlation between the design and measured device parameters is achieved with overall gain of 36 dB at 130 MHz. A clear eye diagram of the hybrid optical receiver using front-illuminated lnGaAs/lnP PIN photodetector is presented indicating its suitability for 155 Mbps optical receiver applications.

Optoelectronic Integreated Circuits for Photonic Systems

Monolithically integrated optoelectronic circuits which combine photonic and electronic devices on the single semiconductor substrate, have the advantages of improved performance, smaller size, low cost and higher reliability as compared to conventional hybrid circuits. This paper reviews the recent developments in both GaAs and InP based optoelectronic integrated circuits. Several key technologies and the issues related to material and integrated processing for optoelectronic integration are addressed. A brief outline of the R&D work already carried out at CEERI in the area of III-V compound semiconductor devices and our future plan is also included.