Response Of Device Research Articles

Effect of carrier heating on chirp and modulation response of directly modulated semiconductor laser diodes

Abstract This paper examines the effect of carrier heating due to hot carrier injection in directly modulated semiconductor laser diodes. Using a single-mode rate equation model including an equation for the energy stored in the conduction band carriers, the changes in carrier temperature due to hot carrier injection from the barrier layer in quantum-well laser diodes are seen to cause a degradation in the device's sinusoidal modulation response. This degradation is coupled with an increase in the wavelength chirp of the light output. It is concluded that in order to minimize the detrimental effect of carrier heating on directly modulated quantum well laser diodes the barrier height should be kept as small as practical. Additionally, the appreciable change in device performance brought about by carrier heating should be accounted for when modelling such devices.

Effect of carrier heating on chirp and modulation response of directly modulated semiconductor laser diodes

This paper examines the effect of carrier heating due to hot carrier injection in directly modulated semiconductor laser diodes. Using a single-mode rate equation model including an equation for the energy stored in the conduction band carriers, the changes in carrier temperature due to hot carrier injection from the barrier layer in quantum-well laser diodes are seen to cause a degradation in the device's sinusoidal modulation response. This degradation is coupled with an increase in the wavelength chirp of the light output. It is concluded that in order to minimize the detrimental effect of carrier heating on directly modulated quantum well laser diodes the barrier height should be kept as small as practical. Additionally, the appreciable change in device performance brought about by carrier heating should be accounted for when modelling such devices.

Optopneumatic Interface for Controlling Pneumatic Power Circuits

This paper presents a study of an optopneumatic interface integrated with a pressure amplifier stage. The interface works using photothermicity to generate a weak pressure signal in its control chambers. In photothermicity, infrared light strikes a black body a few microns thick, increasing the temperature of the black body and air close to it. If this air is in the control chamber of the optopneumatic interface, its expansion generates a pressure control signal, amplified to make it suitable for common low/high commercial pressure valves. This control enables the command of pneumatic actuators in hazardous environments, with the electrical signal transformed into optical and transported using optical fiber; all electrical parts can be located at a distance from direct application. Our results showed that the device's response times, accuracy, and repeatability are suited to many applications. Below is an example of a command integrating electric, optical, and pneumatic techniques and operating by an infrared source with very low light power.

Fast photoconductor CdTe detectors for synchrotron X-ray studies

The Advanced Photon Source will be the brightest source of synchrotron X-rays when it becomes operational in 1996. During normal operation, the ring will be filled with 20 bunches of positrons with an interbunch spacing of 184 ns and a bunch width of 72 ps. To perform experiments with X-rays generated by positrons on these time scales, one needs extremely high speed detectors. To achieve the necessary high speed, we are developing MBE-grown CdTe-based photoconductive position sensitive array detectors. The arrays fabricated have 64 pixels with a gap of 100 μm between the pixels. The high speed response of the devices was tested using a short pulse laser. X-ray static measurements were performed using an X-ray tube and synchrotron radiation to study the device's response to flux and wavelength changes. In this paper, we shall present the response of the devices to some of these tests and also discuss different physics aspects that need to be considered when designing high speed detectors.

Effect of Key Processing Steps on Post Radiation Midgap Voltage

A variety of processing steps were investigated to determine the steps that affect a device's radiation response. Although emphasis is traditionally placed on gate oxide and thermal processing, the physical structure during processing and energetic processes can play a role as well. We find that processing subsequent to the gate oxide layer can have a significant effect on the radiation hardness of a device. Optimizing a process for radiation hardness requires investigation into the entire process and not just optimization of the gate oxide or a set of individual processing steps.

A tunable wavelength-conversion laser

A wavelength-conversion laser was fabricated using monolithic integration of a bistable laser diode and a wavelength-tunable distributed Bragg reflector (DBR) laser. This device converts an input light signal with a certain wavelength to output light with a tunable wavelength over 3.5 nm. Input power required for switching is investigated, and its resonant dependence on input wavelength is revealed. Input polarization is also discussed, and suppression of crosstalk is demonstrated. This device's turn-off switching response is greatly influenced by the light power of the input signal as well as bias current, and the first 1 Gb/s operation is achieved in optimum conditions for fast turn-off and stable turn-on.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Method and apparatus for controlling a keyboard opearated device

First Page

A novel RF-insensitive EED utilizing an integrated metal-oxide-semiconductor structure

The description and characterization of an electroexplosive device (EED) are presented. The structure is designed, using microelectric fabrication techniques, to be inherently immune to radiofrequency (RF) radiation and also offers protection against stray signals associated with RF-induced arcing. A detailed discussion of the structure, which includes the fundamental mechanisms of operation, fabrication techniques, the device's frequency response and sensitivity to RF-induced arcing, and its compatibility with fire control systems, is provided. Preliminary test results of the prototype device are discussed and show a significant improvement in the system's overall EMI immunity. These results include bench and field measurements of the structure's RF response for frequencies of 10-225 MHz and field measurements of the device's sensitivity to RF-induced arcing. The measurements indicate a significant reduction in real power dissipated by an EED employing the structure over an EED employing a conventional bridgewire (20 dB at 90 MHz).< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Carrier transport in semiconductor detectors of magnetic domains

Carrier transport in Hall-type devices detecting magnetic domains is analyzed in terms of a two-dimensional numerical model, using a finite element scheme. The numerical model allows the calculation of magnetic sensitivity for general device geometries or structures, any homogeneous semiconductor material, and arbitrary domain shapes and sizes. We specifically consider three types of commonly used Hall detectors: the conventional Hall plate, the split-electrode Hall device, and the Hall cross. The magnetic sensitivity for these devices is computed for various domain configurations. In particular, the device's output response for moving domains is investigated and appropriate figures of merit are established with respect to spatial resolution. A comparison of the numerical solutions with previously reported experimental results supports the validity of our analysis.

Electro-Optical System Environment Simulation

The evaluation of the interactive nonlinear performance of an electro-optical system is often best achieved by exercising the system in the context of a simulated environment which provides more complex and realistic stimuli than bench tests at less than field testing. The systematic behavior of an electro-optical device, test goals, and simulator resources jointly constrain an appropriate simulation environment. It is the responsibility of the simulation specialist to recognize the peculiar qualities of the object system and to provide for it an environment which, in its relevant characteristics, is practically indistinguishable from the real world, and which is sufficient to exercise the system over its entire stimulus domain. To illustrate this thesis, the location of a hypothetical missile seeker/tracker in the context of a hardware-in-the-loop simulation will be established and the manipulable features of its environment illustrated. Some aspects of such a device's response to its environment which have required special attention will be discussed.