Other

Trw Limited

Northrop Grumman Systems Corporation

Timothy A Vang

David C Scott

Srinath Kalluri

Elizabeth Twyford Kunkee

Michael G Wickham

David V Forbes

Doyle T Nichols

Wenshen Wang

Robert W Lodenkamper

Michael P Nesnidal

A coupled quantum well Mach-Zehnder modulator that employs a push-pull structure to reduce the modulation voltage. The Mach-Zehnder modulator includes a first arm having a first PIN semiconductor device and a second arm having a second PIN semiconductor device. The intrinsic layers of the PIN devices include a coupled quantum well structure to provide an opposite index of refraction change for different DC bias voltages. An RF signal used to modulate the light beam is applied to the two arms in phase and causes the index of refraction in the intrinsic layers of the two PIN devices to change in opposite directions so that a push-pull type drive is achieved without requiring 180&#xb0; out-of-phase RF drive signal.

In-phase RF drive of Mach-Zehnder modulator push-pull electrodes by using coupled quantum well optical active region

A three terminal edge illuminated epilayer waveguide phototransistor including a subcollector layer formed of an epitaxially grown quaternary semiconductor material, such as heavily doped InGaAsP. A collector region of undoped InGaAs is epitaxially grown on the subcollector layer. A base region, including a heavily doped InGaAs base layer and a very thin undoped InGaAs spacer layer, is epitaxially grown on the collector layer. An emitter region, including a doped InGaAsP layer, a doped InP layer, and a heavily doped InGaAs emitter contact layer, is epitaxially grown on the base layer. The various layers and regions are formed so as to define an edge-illuminated facet for receiving incident light.

Three terminal edge illuminated epilayer waveguide phototransistor

Mach-Zehnder modulator with index tuned multimode interference couplers comprising a substrate, an optical input waveguide on the substrate for receiving a light signal, and an input multimode interference coupler. The input multimode interference coupler splits the received light and propagates it down two separate waveguides. Also, the input multimode interference coupler contains electrodes that allow the index of refraction to be tuned. These waveguides contain phase shift regions so that the light signals can be combined at the output multimode interference coupler out of phase. This allows the modulation of the light signal. Also, the output multimode interference coupler contains electrodes that allow the index of refraction to be tuned. The modulated light signal is then outputted through an output waveguide. The tuning of the index of refraction for the input and output multimode interference couplers eliminates the sensitivity of the areas to variations in their geometry.

Mach-Zehnder modulator with individually optimized couplers for optical splitting at the input and optical combining at the output

A monolithically integrated heterojunction bipolar transistor optoelectronic transimpedance amplifier using the first transistor as an optical detector. An edge illuminated epilayer waveguide phototransistor is used as the light-detecting element. The phototransistor is used as an optical detector in which the incident light pulses are converted to electrical pulses and then amplified for further signal processing. The phototransistor is monolithically integrated on the same material substrate as the emitter follower amplifier so that the parasitics normally associated with receiver circuitry are minimized. By eliminating the parasitic impedances, the circuit can be used as a receiver in high bit rate optical communication systems.

Heterojunction bipolar transistor optoelectronic transimpedance amplifier using the first transistor as an optical detector

An edge illuminated epilayer waveguide phototransistor including a subcollector layer formed from an epitaxially grown quaternary semiconductor material, such as heavily doped InGaAsP. A collector region of undoped InGaAs is epitaxially grown on the subcollector layer. A base region of moderately doped InGaAs is epitaxially grown on the collector layer. An emitter region, including a doped InGaAsP layer, a doped InP layer, and a heavily doped InGaAs emitter contact layer, is epitaxially grown on the base layer. The various layers and regions are formed so as to define an edge-illuminated facet for receiving incident light. Also, the base does not have an ohmic contact so that the base thickness can be minimized. Finally, the base doping concentration is minimized so that the gain-bandwidth product can be maximized.

Two terminal edge illuminated epilayer waveguide phototransistor

A waveguide ( ) is provided having a two-dimensional optical wavelength Bragg grating ( ) embedded within a semiconductor laser medium ( ). More particularly, the waveguide ( ) includes an active region ( ) sandwiched between n-doped and p-doped cladding layers ( ). The two-dimensional Bragg grating ( ) is formed in the active region ( ). Upper and lower electrodes ( ) are defined on opposite sides of the cladding layers ( ) to complete the waveguide structure ( ). The two-dimensional grating ( ) provides simultaneous frequency selective feedback for mode control in both the longitudinal and lateral directions.

High power single mode semiconductor lasers and optical amplifiers using 2D Bragg gratings

A metal-semiconductor-metal photodetector (,) is provided including an optical waveguide (,) disposed on a substrate (,) and an array of metal-semiconductor-metal photodiodes (,) coupled to the optical waveguide (,). An absorber (,) is disposed between the photodiodes (,) and the optical waveguide (,) and a transmission line (,) is coupled to the photodiodes (,). Each of the photodiodes (,) includes an electrode (,) having a plurality of interdigitated electrode fingers (,) wherein a width of each finger (,) and a gap between adjacent fingers (,) tapers from one end of the electrode (,) to the other. Preferably the rate of tapering corresponds to an exponential rate of optical power decay through the photodiode (,). In this way, both the photocurrent density in the fingers (,) and the uniformity of the electric field underneath the electrodes (,) are optimized.

Variable electrode traveling wave metal-semiconductor-metal waveguide photodetector

An optical waveguide device (30) that limits the peak optical intensity applied to an optical absorbing device (36), such as a photodetector or electro-absorption modulator. The optical waveguide device (30) includes a single mode input waveguide (34) coupled to a multi-mode, waveguide interference coupler (32). A single mode output waveguide (38) collects the light from the interference coupler (32). The absorbing device (36) is defined in the waveguide coupler (32) by a reverse-biased p-i-n diode structure. A voltage potential applied to the diode structure creates an electric field across the waveguide coupler (32) that causes the waveguide coupler (32) to absorb. Light entering the interference coupler (32) from the single mode waveguide (34) expands into other propagation modes that interact to constructively and destructively interfere. Because the light expands in the coupler (32), the amplitude of the light decreases even though the overall power remains substantially the same. When the light recombines as it approaches the output waveguide (38), the amplitude of the light returns to the input amplitude. The absorbing device (36) is defined in the waveguide coupler (32) between the area of interference (24) and the output waveguide (38). The absorption in the absorbing device (36) is exponential; the most light is absorbed at first and then progressively less light along the device.

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San Dimas, CA, United States of America

Timothy A Vang