Abstract: A lateral injection VCSEL comprises upper and lower mirrors forming a cavity resonator, an active region disposed in the resonator, high conductivity upper and lower contact layers located on opposite sides of the active region, upper and lower electrodes disposed on the upper and lower contact layers, respectively, and on laterally opposite sides of the upper mirror, and a current guide structure including an apertured high resistivity layer for constraining current to flow in a relatively narrow channel through the active region, characterized in that a portion of the lower contact layer that extends under the top electrode has relatively high resistivity. This feature of our invention serves two purposes. First, it suppresses current flow in parallel paths and, therefore, tends to make the current density distribution in the aperture more favorable for the fundamental mode. Second, it reduces parasitic capacitance.

Abstract: A non-hermetic APD for operation in a moisture-containing ambient comprises an InP/InGaAsP-containing Group III-V compound semiconductor body and a p-n junction formed in the body. Typically the junction intersects a top surface of the body. A patterned dielectric layer is formed on the surface so as to cover at least those regions of the surface that are intersected by the junction. An electrode is formed in an opening in the dielectric layer so as to make electrical contact with one side of the junction. Importantly, the thickness of the dielectric layer is sufficient to reduce the leakage current through it to less than about 1 nA when the operating voltage is in the range of about 20-100 V. In accordance with a preferred embodiment, the thickness of the dielectric layer is greater than about 2 &mgr;m when the applied voltage is in excess of about 20 V. Moreover, the composition of dielectric layer may be either inorganic (e.g., a silicon nitride) or a combination of inorganic and organic materials.

Abstract: The thermo-optic behavior of an optical path over a range of temperatures &Dgr;T is controlled by determining a figure-of-merit (FOM) for the optical path and including in the path a body of crystalline material that enables the conditions specified by the FOM to be satisfied. The crystalline material is highly transparent at a wavelength &lgr; of radiation propagating in the path, and it has a coefficient of thermal expansion (CTE) and a refractive index n such that the CTE and dn/dT are mutually adapted to satisfy the FOM over the range &Dgr;T. In one embodiment, the CTE and dn/dT of an etalon compensate one another so as to perform frequency discrimination that is essentially temperature insensitive over the range &Dgr;T. In a preferred embodiment of the optical etalon the crystalline material comprises LiCaAlF6.

Abstract: In a mesa geometry semiconductor laser, a patterned dielectric coating used to define the stripe geometry contact on the top the mesa and to provide significant waveguiding comprises a chalcogenide glass. Applications to intersubband (e.g., quantum cascade) lasers are specifically described.

Abstract: We have discovered that, contrary to conventional wisdom about forming DP defects, electrical saturation in highly doped 2D layers of Si does not occur. In accordance with one aspect of our invention, free-carrier concentrations in excess of about 7×1020 cm−3 can be attained in single crystal Si layers &dgr;-doped with a Group V element. In one embodiment, free-carrier concentrations in excess of about 2×1021 cm−3 are realized in single crystal Si that is &dgr;-doped with Sb. In another embodiment, the &dgr;-doped layer is formed as an integral part of an FET.

Abstract: A properly designed MOF can simultaneously exhibit large anomalous dispersion at visible and near infrared wavelengths and support numerous transverse spatial modes that are essentially decoupled from one another, even in the presence of significant perturbations. In a MOF that includes an inner cladding region comprising at least one thin layer of air holes surrounding a core region, the key is to achieve a relatively large wave vector mismatch between the lowest order modes by appropriate design of the size of the core region and of the effective refractive index difference between the core region and the inner cladding region. In accordance with one aspect of our invention, MOFs are designed to exhibit simultaneously relatively large anomalous dispersion and essentially decoupled transverse spatial modes by making the diameter of the core region less than about 6 &mgr;m and the difference in effective refractive index between the core and cladding regions greater than about 0.1 (10%).

Abstract: A fiber optic system comprises an optical transmitter, an optical receiver, and an optical fiber transmission path that optically couples the transmitter and the receiver to one another. The transmission path includes a first section that has negative dispersion at an operating wavelength &lgr;0 greater than about 1300 nm and a second section that includes a MOF. The MOF has relatively large anomalous dispersion at &lgr;0 and is sufficiently long to compensate the accumulated negative dispersion in the first section. In one embodiment the MOF comprises a core, a lower index cladding that includes one or more layers of air holes surrounding the core, characterized in that the diameter of the core is less than about 8 &mgr;m and the difference in effective refractive index between the core and cladding is greater than about 0.1 (10%). Preferably, the cladding contains no more than 2 layers of air holes and the distance between the nearest edges of adjacent air holes is less than about 1 &mgr;m.

Abstract: A self-modulated solid state laser comprises an intracavity optical waveguide that supports a multiplicity of lasing filaments each at a different optical frequency. At least two of the filaments temporally beat with one another so as to modulate the intensity of the laser output. In accordance with one embodiment of our invention, the waveguide supports a multiplicity of transverse modes, and the laser includes a mode mixing mechanism that mixes the energy of at least two pairs of the modes, each coupled pair generating a separate filament. In an illustrative embodiment, the filaments are mode locked and the laser output is modulated at a frequency on the order of 1 THz.

Abstract: A method of fabricating an IC comprises the steps of: (a) forming trench isolation regions in a surface of a semiconductor body; and (b) forming a tub-tie region between at least one pair of the trench isolation regions (when viewed in cross-section) by a process that includes the following steps: (b1) forming a first photolithographic mask that covers and is in registration with the tub-tie region; (b2) implanting ions of a first conductivity-type to form a tub region adjacent the tub-tie region; (b3) removing the first mask; (b4) forming a second photolithographic mask that has an opening that exposes most of the underlying tub-tie region but overlaps a first peripheral section on one side of the tub-tie region; (b5) implanting ions to form a pedestal portion of a second conductivity-type within the tub-tie region; and (b6) implanting ions of the first conductivity-type at an acute (preferably non-zero) angle −⊕ with respect to the normal to the surface to the body so as to form a conductivity-t

Abstract: A solid state laser comprises a cavity resonator in the form of a generally cylindrical body and, located within the resonator, an active region which generates lasing light when suitably pumped. The resonator has a relatively high effective refractive index (n>2 and typically n>3) is sufficiently deformed from circularity so as to support at least one librational mode (e.g., a V-shaped or a bow-tie mode, the latter being presently preferred for generating relatively high power, directional outputs). Specifically described is a Group III-V compound semiconductor, quantum cascade (QC), micro-cylinder laser in which the resonator has a flattened quadrupolar deformation from circularity. This laser exhibits both a highly directional output emission and a three-order of magnitude increase in optical output power compared to conventional semiconductor micro-cylinder QC lasers having circularly symmetric resonators.

Abstract: A tunable semiconductor laser comprises a gain section having an MQW active region, a uniform pitch grating DFB region, and first waveguide. A composite reflector, including a second MQW region and a second waveguide, forms a cavity resonator with the DFB region. A tuning voltage applied to the composite reflector induces refractive index changes, thereby allowing the center wavelength to be altered.

Abstract: A mounting technology that increases the cw operating temperature of intersubband lasers, without increasing the risk of hot spots near the facets and short circuits near the perimeter of the laser chip, is described.

Abstract: An intersubband semiconductor light source comprises a core region that includes a unipolar, radiative transition (RT) region having upper and lower energy levels, an injector-only (I) region disposed on one side of the RT region, and a reflector/extractor-only (R/E) region disposed on the other side of the RT region. The I region has a first miniband of energy levels aligned so as to inject electrons into the upper energy level, and the R/E region has a second miniband of energy levels aligned so as to extract electrons from the lower energy level. The R/E region also has a minigap aligned so as to inhibit the extraction of electrons from the upper level. A suitable voltage applied across the core region is effective to cause the RT region to generate light at a wavelength determined by the energy difference between the upper and lower energy levels. Low voltage operation at less than 3 V is described.

Abstract: Optical detection apparatus comprises a solid state laser having an intracavity optical waveguide that supports a lasing filament and operates in one of two states: (1) in a first state, the filament is fixed in one of two orientations, and (2) in a second state, the filament may be induced to switch or oscillate between the two orientations, or it may be suppressed altogether. At least one feature is located on the output facet off-center with respect to the waveguide cross-section in order to provide a preferred orientation for the filament. In one embodiment, a single feature is located off-center and optical radiation of one intensity is injected through the facet feature, thereby causing the laser to operate in one of its states, whereas injected radiation of another intensity causes the laser to operate in the other of its states. The injected radiation may be radiation emitted by the laser that is reflected by an object (e.g.

Abstract: A long wavelength (e.g., mid-IR to far-IR) semiconductor laser comprises an active region and at least one cladding region characterized in that the cladding region includes a light guiding interface between two materials which have dielectric constants opposite in sign. Consequently, the guided modes are transverse magnetic polarized surface waves (i.e., surface plasmons) which propagate along the interface without the need for a traditional dielectric cladding. In a preferred embodiment, the interface is formed between a semiconductor layer and a metal layer. The complex refractive index of the metal layer preferably has an imaginary component which is much larger than its real component. In an illustrative embodiment, our laser includes a QC active region sandwiched between a pair of cladding regions one of which is a guiding interface based on surface plasmons and the other of which is a dielectric (e.g., semiconductor) structure.

Abstract: An IC comprises a pair of circuit nodes, a current mirror that includes dual-function transistor, and a controller for switching the transistor between a pair of states. In a first state, the transistor provides current gain and also provides a relatively high impedance between the nodes, and in a second state, it provides no current gain and a relatively lower impedance between the nodes.

Abstract: An MQW laser comprises an active region in which a multiplicity of barriers each includes a doped barrier layer separated from its adjacent quantum well layers by undoped barrier layers. In a preferred embodiment, each barrier of an InGaAsP/InP SCH MQW laser includes a p-type (e.g., Be, Mg or C) delta-doped InGaAsP barrier layer sandwiched between a pair of undoped InGaAsP barrier layers. With suitable doping concentration and thickness of the delta-doped barrier layer, we have demonstrated MQW lasers with To as high as 82 K.

Abstract: An optical transmitter for generating any one of N carrier signals for use in an M-channel WDM system (M≧N), each channel operating at a different carrier wavelength &lgr;s (s=1, 2 . . . M), includes an optical source for generating the carrier signals at any one of multiplicity of N wavelengths &lgr;i (i=1, 2 . . . N), where (1≦N≦M). A first controller selects a particular one of the wavelengths &lgr;i at which the source operates. An optical modulator receives the carrier signal corresponding to the selected wavelength &lgr;i and impresses information on the received signal. The modulator has a characteristic electronic bandgap and a wavelength &lgr;g corresponding thereto. At a given temperature, &lgr;g is offset from each &lgr;i by an amount &Dgr;&lgr;i. For each wavelength &lgr;i there is a predetermined value of &Dgr;&lgr;i which delivers preferred (e.g., optimum) transmission performance.

Abstract: In a multi-layered dielectric mirror the higher refractive index layers comprise ZnS and the lower refractive index layers comprise a composite of approximately 95%MgF2 and 5%CaF2 by mole fraction. In one embodiment, the fluoride layers are e-beam deposited from an essentially eutectic melt of the two fluorides. In another embodiment, the semiconductor surface on which the mirror is formed is protected by an aluminum borosilicate glass layer. Application of the invention to the design and fabrication of VCSELs is also described.

Abstract: A VCSEL comprises separate current and optical guides that provide unique forms of drive current and transverse mode confinement, respectively. In one embodiment, the optical guide comprises an intracavity high refractive index mesa disposed transverse to the cavity resonator axis and a multi-layered dielectric (i.e., non-epitaxial) mirror overlaying the mesa. In another embodiment, the current guide comprises an annular first electrode which laterally surrounds the mesa but has an inside diameter which is greater than that of an ion-implantation-defined current aperture. The current guide causes current to flow laterally from the first electrode along a first path segment which is essentially perpendicular to the resonator axis, then vertically from the first segment along a second path segment essentially parallel to that axis, and finally through the current aperture and the active region to a second electrode.