Abstract: 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° out-of-phase RF drive signal.

Abstract: A Mach-Zehnder modulator that employs quantum dots to provide a push-pull drive operation. The Mach-Zehnder modulator includes a first arm having a first PIN semiconductor device and a second arm having a second PIN semiconductor device, where the intrinsic layers of the PIN devices include a quantum dot structure. A first DC bias signal is applied to one of the PIN devices, and a second DC bias signal is applied to the other PIN device. The first DC bias signal biases the intrinsic layer at an operating voltage where the index of refraction of the intrinsic layer is at a positive portion of an electro-refraction transfer function, and the second DC bias potential biases the intrinsic layer at an operating voltage where the index of refraction of the intrinsic layer is at a negative portion of the transfer function.

Abstract: A single-electrode, push-pull semiconductor PIN Mach-Zehnder modulator (10) that includes first and second PIN devices (12, 14) on a substrate (16). Intrinsic layers (22, 28) of the devices (12, 14) are the active regions of two arms (50, 52) of a Mach-Zehnder interferometer. An outer electrode (38) is connected to the N layer (24) of the first PIN device (12) and a center electrode (40) is connected to the P layer (20) of the first PIN device (12). An outer electrode (42) is connected to the P layer (26) of the second PIN device (14) and the center electrode (40) is connected to the N layer (30) of the second PIN device (14). An RF modulation signal biases the PIN devices (12, 14) in opposite directions and causes the index refraction of the intrinsic layers (22, 28) to change in opposite directions to give a push-pull modulation effect.

Abstract: 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° out-of-phase RF drive signal.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A waveguide (10) is provided having a two-dimensional optical wavelength Bragg grating (20) embedded within a semiconductor laser medium (16). More particularly, the waveguide (10) includes an active region (16) sandwiched between n-doped and p-doped cladding layers (14, 22). The two-dimensional Bragg grating (20) is formed in the active region (16). Upper and lower electrodes (24, 26) are defined on opposite sides of the cladding layers (14, 22) to complete the waveguide structure (10). The two-dimensional grating (20) provides simultaneous frequency selective feedback for mode control in both the longitudinal and lateral directions.

Abstract: A metal-semiconductor-metal photodetector (18) is provided including an optical waveguide (22) disposed on a substrate (28) and an array of metal-semiconductor-metal photodiodes (20) coupled to the optical waveguide (22). An absorber (30) is disposed between the photodiodes (20) and the optical waveguide (22) and a transmission line (26) is coupled to the photodiodes (20). Each of the photodiodes (20) includes an electrode (24) having a plurality of interdigitated electrode fingers (31) wherein a width of each finger (31) and a gap between adjacent fingers (31) tapers from one end of the electrode (24) to the other. Preferably the rate of tapering corresponds to an exponential rate of optical power decay through the photodiode (20). In this way, both the photocurrent density in the fingers (31) and the uniformity of the electric field underneath the electrodes (24) are optimized.

Abstract: 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.

Abstract: An optoelectronic switching node is disclosed wherein two input optical beams can be switched in the sense that they can be regenerated in either one of two output spatial locations in response to input control signals. Each one of the input optical beams is coupled to a resonant cavity detector which generates a current when its corresponding optical beam impinges on its resonant cavity. Output optical beams are regenerated by two inversion channel lasers each one of which has emitter, source and sub-collector terminals and is bistable in the sense that it can be switched on and off by currents delivered into and taken out of its source terminal. Heterojunction field effect transistors are used to selectively couple the currents generated by the resonant cavity detectors to the source terminals of the lasers in order to turn them on.