Abstract: An optical modulator comprises at least two optically coupled MARS modulators, at least one having positive spectral tilt and at least one having negative spectral tilt. Both tilt and attenuation can be independently controlled by adjusting the air gaps of the constituent modulators. Preferred designs present linear spectral tilt.

Abstract: A method for thermocompression bonding structures together including structures having different coefficients of thermal expansion, for example, thermocompression bonding optical diode arrays or other semiconductor structures to silicon substrates to form electronic or optoelectronic devices. The method includes aligning and contacting the structures to be interconnected, thermocompressing the structures via their contact pad elements at a bonding temperature, establishing an encapsulation temperature, applying an encapsulant material between the bonded structures, and curing the encapsulant material at the encapsulation temperature. Conventional bonding processes, which treat encapsulation as a separate step apart from bonding processes, melt the bonded assembly together and include at least one thermal cycle in which the bonded assembly is cooled to room temperature and then is re-heated to the encapsulation temperature before applying the encapsulant material.

Abstract: Each of a plurality of photodiodes forming a photodetector is mounted on a respective metal pad on the surface of a semiconductor integrated circuit chip including a corresponding number of amplifier circuits for detecting the photocurrent from respective photodiodes. Each circuit comprises a high gain, high input impedance amplifier and a feedback element, typically a resistor of high value, connected across the amplifier between input and output nodes thereof. Each photodiode mounting metal pad and each feedback resistor is connected to a common input node of a respective amplifier by metal paths within a connecting structure forming part of the integrated circuit. Adverse effects on the output current from the photodiodes are reduced by forming a junction of the path from each feedback resistor with the path from the corresponding photodiode at the metal pad on which the photodiode is mounted, and interconnecting such junction along a common path to the corresponding amplifier input node.

Abstract: The specification describes a technique for solder bump bonding IC chips or chip packages to interconnection substrates. Epoxy prepolymer underfill is applied to the surface of the interconnection substrate prior to the solder bump bonding step. The presence of the prepolymer underfill material does not interfere with effective bonding. This technique reduces substantially the potential for voids in the underfill layer that tend to occur when the underfill is applied to a bonded IC chip/substrate assembly. It also enables curing of the underfill polymer in the same heating step used to effect thermocompression bonding of the solder bumps.

Abstract: A detector array for detecting an optical signal includes a plurality of pixels. Each pixel has a plurality of detector elements coupled together in a redundant configuration such that the detector array maintains a substantially uniform response even if each of the pixels includes a number of defective detector elements. The optical signal is lengthened in the direction normal to the information vector, so that each detector element is exposed to the same portion of the optical signal. A bad-element sensor is coupled to each detector element, which is functionally responsive to the detection of a bad detector element.

Abstract: The specification describes a double poly Mechanical Anti-Reflection Switch (MARS) device in which shorting between the lower poly metallization and the silicon substrate is prevented by providing an insulating layer on the surface of the silicon substrate.

Abstract: A wavelength demultiplexer having at least two photodetectors is disclosed. The photodetectors are arranged in sequential layers along an optical path. The photodetectors differ in bandgap, and are arranged so that the optical signal passes through relatively larger bandgap photodetectors before being received by relatively smaller bandgap detectors. Each photodetector absorbs photons within a predetermined energy range and generates a voltage as a function of the absorbed energy. The photodetectors can be used to detect, and hence demultiplex, a wavelength-division-multiplexed signal.

Abstract: A micro-mechanical, anti-reflective, switched optical modular array that utilizes a continuous, uninterrupted modular membrane across an array of individual modulators. The individual modulators are positioned within an optical window of the device, the optical window being defined by a region of the membrane situated between an array of electrode pairs, where an individual pair of electrodes is used to control an individual one of the modulators. Alternative electrode shapes and fabrication methods are described.

Abstract: The specification describes a double poly Mechanical Anti-Reflection Switch (MARS) device in which transition layers of SiN.sub.x are provided on either side of the air gap, and the thickness ratio of the two transition layers is adjusted to provide a tradeoff between the insertion loss of the device and the optical bandwidth.

Abstract: The specification describes a process for growing device quality III-V heteroepitaxial layers without the use of buffer layers, i.e. largely defect free layers with thicknesses greater than 50 Angstroms directly on the III-V substrate. These high quality heteroepitaxial layers are grown by low temperature MBE.

Abstract: In a method of making a flip-chip bonded GaAs-based opto-electronic device, removal of the GaAs substrate is facilitated by provision of a lattice matched (Al.sub.x Ga.sub.1-x)InP etch stop layer, exemplarily a Ga.sub.0.51 In.sub.0.49 P layer, and use of an etchant that isotropically etches GaAs such that an essentially mirror-like etch stop layer surface results, and that preferably exhibits an etch rate ratio of at least 200:1 for GaAs and the etch stop layer, respectively. Use of the novel substrate removal method can substantially increase device yield, and facilitate manufacture of large device arrays, e.g., arrays of detector/modulator diodes flip-chip bonded to Si CMOS chips.

Abstract: Each microminiature contact pad included in a dense array of pads on an electronic component contains a relatively thick layer of solder. The layer is treated to form a relatively thin brittle protective layer on the surface of the solder. The structure is then brought into contact with a contact pad in a mating array of pads on another component in a thermo-compression bonding step carried out below the melting point of the solder. In that step, the brittle layer is fractured. As a result, solid-state diffusion of conductive material occurs through fissures in the fractured layer, thereby to provide an electrical connection between mating pads on the two components.

Abstract: A mechanical modulator is provided that includes a conductive substrate and at least three multilayer mirrors disposed on the substrate. The mirrors are spaced apart from one another to define upper and lower optical cavities. The upper cavity is formed by an airgap having a variable thickness. The multilayer mirror located above the airgap includes a conductive membrane having an optically transparent portion and a flexible support for orienting the membrane in a first position. Under the action of a bias, the membrane moves to a second position, changing the air gap by a fraction of a wavelength of the optical signal, as measured in air. The change in position of the membrane from the first to the second position causes a change in the total reflectivity of the modulator from a minimum to a maximum value.

Abstract: A level-setting attenuator for generating an output signal having a predetermined optical power from an input optical signal having a varying power is disclosed. The level-setting attenuator includes a telecentric imaging device, a variable atttenuator, an optical power detector and control electronics. The telecentric imaging device collimates a received optical signal which is received and partially attenuated by the variable attenuator. In some embodiments, the variable attenuator generates an attenuated signal portion and an unattenuated signal portion. The attenuated signal is directed, by the variable attenuator, to an optical power detector operable to measure the power of the attenuated optical signal. The detector sends a signal indicative of the measurement to control electronics. The control electronics are operable to generate a control signal for controlling the attenuation of the unattenuated signal portion so that is has the predetermined power level.

Abstract: In an improved method for manufacturing an integrated composite semiconductor device according to the present invention, a semiconductor-based stop-etch layer having holes therein at selected sites is disposed over the epoxy or other flowable hardener used in flip-chip bonding. The hardener underneath the openings in the stop-etch layer is subtantially removed via a dry etch applied therethrough, exposing desired structure, such as bonding pads, formerly covered by the hardener. The epoxy underneath the stop-etch layer is substantially preserved.

Abstract: Optoelectronic devices such as photodetectors, modulators and lasers with improved optical properties are provided with an atomically smooth transition between the buried conductive layer and quantum-well-diode-containing intrinsic region of a p-i-n structure. The buried conductive layer is grown on an underlying substrate utilizing a surfactant-assisted growth technique. The dopant and dopant concentration are selected, as a function of the thickness of the conductive layer to be formed, so that a surface impurity concentration of from 0.1 to 1 monolayer of dopant atoms is provided. The presence of the impurities promotes atomic ordering at the interface between the conductive layer and the intrinsic region, and subsequently results in sharp barriers between the alternating layers comprising the quantum-well-diodes of the intrinsic layer.

Abstract: A modulator having low insertion and a broad operating bandwidth is disclosed. The modulator has a movable membrane that is spaced from a substrate. The reflectivity of the movable membrane, and the reflectivity of the subtrate/gap interface are unequal. In particular, relative to the membrane, the substrate has a lower reflectivity. Device finesse is dictated by the lower reflectivity "mirror," i.e., the substrate. The substrate configuration thus provides a broad operating bandwidth while the higher reflectivity membrane provides low insertion loss.

Abstract: A hybrid chip having at least two different types of semiconductor devices co-located on a common substrate, and a method therefor, are disclosed. The devices have different multiple epitaxial layer structures so that each different type of device is first grown on a separate appropriately-selected substrate, and then attached to the common substrate. According to the method, a first device is attached to the common substrate using flip-chip bonding methods. Flip-chip bonding involves attaching the device and the substrate at bonding pads, flowing a flowable hardener between the first device and the common substrate and allowing it to harden, and then removing the substrate upon which the first device was grown. The hardener is removed before attaching the second type of device via flip-chip bonding.

Abstract: A micromechanical optical modulator having a linear response in reflectivity, as a function of applied bias, and a method of operating and making same, are disclosed. The modulator consists of a movable layer suspended over a substrate. A gap is defined between the movable layer and the substrate. As the movable layer moves, the gap changes size, resulting in a change in modulator reflectivity. In operation, the movable layer moves within a linear operating regime under the action of an applied voltage, which is the sum of a constant bias and a signal from an analog source. A substantially linear operating characteristic, i.e., reflectivity versus applied voltage is obtained within the linear operating regime by properly selecting the size of the gap in the absence of the applied voltage and the range in the applied voltage.

Abstract: An apparatus for modulating an optical signal and a method for fabricating such an apparatus, are disclosed. The apparatus, which may be formed on a semiconductor wafer or chip, consists of a membrane that is supported over a substrate by flexible support arms. An air gap is defined between the membrane and substrate. The membrane thickness and refractive index are chosen so that the reflectivities of the membrane and substrate are not 180.degree. out of phase. Under the action of bias, the membrane moves vertically from a first position to a second position relative to the substrate, changing the air gap. The reflectivity of the modulator changes as the air gap changes. Membrane thickness and the air gap are suitably selected to achieve zero overall modulator reflectivity in one of the two membrane positions. Equations define acceptable values for the thickness of the membrane thickness and the air gap. The membrane and air gap are formed by various etching and photolithographic methods.