Abstract: The present invention is directed to improving the efficiency of removing heat from semiconductor devices. In addition, the method of manufacturing the improved devices has the potential of eliminating a key step in the traditional production process where the chips are highly susceptible to mechanical damage. A semiconductor element includes a semiconductor substrate having a heat removal side and a heat producing region, and at least one superstrate semiconductor layer defining the heat producing region. The heat removal side of the semiconductor substrate includes at least one recess region which extends closer to the heat-generating region than the remainder of the heat removal surface.

Abstract: The present invention relates to a device for use in a fiber optic system that may be a communication system, a sensing system or other system using guided-wave optical components. Reducing the number of lenses required to couple the waveguides and the free-space paths in the device offers the dual advantages of a reduced component count and simplified alignment. In an exemplary device having a first and second waveguides, a birefringent optical system defines bi-directional, polarization-dependent free-space paths. One of the bidirectional, polarization-dependent, free-space paths couples at least the first waveguide to the second waveguide. The birefringent optical system includes at least one prism for bending one of the polarization-dependent paths in a clockwise direction and one of the polarization-dependent paths in a counterclockwise direction.

Abstract: The present invention relates to a device for use in a fiber optic system that may be a communication system, a sensing system or other system using guided-wave optical components. Reducing the number of lenses required to couple the waveguides and the free-space paths in the device offers the dual advantages of a reduced component count and simplified alignment. In an exemplary device having a first and second waveguides, a birefringent optical system defines bi-directional, polarization-dependent free-space paths. One of the bi-directional, polarization-dependent, free-space paths couples at least the first waveguide to the second waveguide. The birefringent optical system includes at least one prism for bending one of the polarization-dependent paths in a clockwise direction and one of the polarization-dependent paths in a counterclockwise direction.

Abstract: A method for locking the wavelength of a laser uses a non-planar etalon, for example a non-parallel etalon, to produce a periodic spatial interference pattern, typically in the light reflected from the non-planar etalon. At least three different portions of the interference pattern are detected to generate at least three respective detection signals. A feedback signal is generated using the detection signals, and the operating wavelength of the laser is adjusted in response to the feedback signal.

Abstract: In order to reduce the possibility of a laser operating in multiple transverse modes at high power, the laser is provided with laterally asymmetric losses that discriminate against modes higher than the fundamental mode. One approach to doing this is form an asymmetric ridge waveguide in the laser, that allows the light of the higher order modes to leak out of the waveguide.

Abstract: A compact, in-line polarization combiner uses a folded, reflective optical path from a first fiber to a second fiber. The combiner includes first and second fibers at one end of an in-line package, and a third fiber at the other end of the in-line package. A first polarization-dependent optical path is defined between the first and second fibers for light in a first polarization state. A second polarization-dependent path is defined between the first and third fibers for light in a second polarization state orthogonal to the first polarization state. A polarizer is disposed between the ends of the combiner and reflects light on the first path between the first and second fibers and transmits light on the second path between the first and third ports, A reflector is disposed on the first path to reflect light to the polarizer.

Abstract: An apparatus for locking the wavelength of a laser uses a non-planar etalon, for example a non-parallel etalon, to produce a periodic spatial interference pattern, typically in the light reflected from the etalon. The apparatus also uses a detector to detect the spatial interference pattern having at least three separate detector elements, commonly referred to as pixels. The etalon and the detector are matched to each other so that adjacent pixels detect a specific portion of the phase of the periodic interference pattern.

Abstract: An improved fiber optic tap monitor has characteristics that are flatter over the wavelength range of interest. The polarization dependence of the characteristics of the tap monitor is reduced, and the package for the tap monitor is smaller. The tap monitor reduces the amount of light reflected back to the source. The tap monitor is also assembled in a manner to improve temperature stability, so that its characteristics over a range of temperatures are more nearly constant.

Abstract: An interferometer uses birefringent elements for splitting and combining beams of orthogonal polarization, and for changing the relative phase between the orthogonally polarized beams. A polarization sensitive detector is used to detect a fringe pattern whose periodicity is dependent on the relative optical paths traversed by the orthogonally polarized beams. In an embodiment of the invention, a birefringent beam splitter has an input path and first and second output paths. A birefringent beam combiner has first and second input paths and an output path, the first and second input paths of the birefringent beam combiner aligned respectively with the first and second output paths of the birefringent beam splitter. A polarization sensitive detector is disposed on the output path of the birefringent beam combiner to detect the periodicity of the fringe pattern.

Abstract: The invention relates to an approach to angle tuning a thin film, interference filter device in which light is delivered to the filter from a fiber lying off-axis relative to the filter, and to a method of optically coupling such a device. The optical device comprises a lens unit having an optical axis and an adjustable effective focal length. The device also includes a first port disposed on a first side of the lens unit and on a first side of the optical axis, and an optical element disposed on the second side of the lens unit. The optical element has an optical characteristic that is dependent on the angle of incidence on the optical element. The lens unit has an adjustable focal length so light from the first port is incident on the optical element at a desired angle.

Abstract: Two sub-assemblies in a fiber optic device are fitted to mounting faces of a central section. The mounting faces are typically flat and mutually orthogonal, thus permitting the adjustment of the two sub-assemblies in decoupled degrees of freedom. This results in a simpler adjustment procedure for aligning the two sub-assemblies. Furthermore, the mounting of the sub-assemblies using the orthogonal mounting faces permits the use of relatively thin layers of adhesive that reduce misalignment problems arising from mismatched thermal expansion when the temperature changes.

Abstract: An approach for compensating for losses in a tunable laser filter comprising includes providing a tunable waveguide material and an amplifying material that have different compositions. The tuning material and the amplifying material are placed parallel to one another. The amplifying material is disposed so that it covers the tuning material at discrete locations. Carriers are injected simultaneously into both materials. The tuning material is spaced from the amplifying material at an average distance that is greater than the charge carrier diffusion length, so as to reduce avoid diffusion of charge carriers from the tuning material into the amplifying material. This prevents the amplifying material draining the charge carriers out of the tuning material, thus enabling the refractive index of the tuning material to be tuned for a desired wavelength effect.

Abstract: A method of frequency and mode stabilizing a tuneable laser, wherein one or more measurable magnitudes is/are measured, wherein the laser has been characterized with respect to a number of operation points, and wherein the values of the measurable magnitude or magnitudes are stored in a microprocessor or corresponding device. The invention is characterized by causing the values of one or more of the measurable magnitudes to be non-extreme values; storing the values of such non-extreme values as a quotient where the numerator is the derivative of a measurable magnitude ?Y with respect to a control current ?I to one laser section, and where the denominator is the derivative of another measurable magnitude ?Z with respect to said control current ?I; and using the stored values to control the laser to a desired operation point.

Abstract: Generally, the present invention relates to a fiber optic device that is easier to align than conventional devices, and to a method for aligning such devices. An embodiment of the invention includes a first focusing element having an optical axis and a first focal length, and a first optical fiber optically coupled to a first side of the first focusing element. The first optical fiber is disposed at a first transverse distance from the optical axis so that light from the first optical fiber propagates on a second side of the first focusing element as a substantially collimated beam at a first angle to the optical axis. A wedged optical element is optically coupled to the second side of the first focusing element and deviates the substantially collimated beam so as to propagate in a direction substantially parallel to the optical axis.

Abstract: In an apparatus and method for locking the wavelength of a laser, a fringe-producing optical element is disposed directly in the in the output beam from the laser. The fringe-producing optical element produces a fringe pattern in a second light beam derived from the output beam. The fringe pattern is detected by a detector unit. Signals generated by the detector unit are used to generate a laser tuning control signal that tunes the laser to a desired operating wavelength.

Abstract: A particular focusing arrangement in a dual fiber collimator improves the transmission efficiency and ease of alignment of the collimator. In particular, the collimator includes two optical fibers mounted in a dual-fiber ferrule. The fiber end-faces are co-planar with the angle-polished end-face of the ferrule and displaced along the optical axis of the ferrule. The collimator unit also includes a first focusing element centered along the optical axis of the ferrule and positioned such that its back front focal point is between the two end faces of the fibers. An advantage provided by this arrangement is that by changing the fiber polish angle and polish azimuth, relative to a line connecting the fiber centers, superior coupling from one fiber to the other can be achieved, even with different working distances and at various wavelengths.

Abstract: A method of evaluating a tuneable laser and determining suitable laser operation points. Part of the light emitted by the laser is led to a Fabry-Perot filter and to a pair of light detectors to measure the power of the laser and deliver a corresponding output signal representative of the wavelength of the detected light. Injected currents are swept through the laser tuning sections to pass through different current combinations, and the ratio between the detector signals is measured during the sweep of the reflector current in both directions. The control combination for the tuning currents is stored when the ratio between the detector output signals lies within a predetermined range signifying that the emitted light lies within one of a number of wavelengths given by the Fabry-Perot filter, and the ratio lies within the predetermined range for a given reflector current in both sweep directions of the reflector current.

Abstract: A wide band reflector, for example a wideband grating reflector is provided as the output coupler of a semiconductor laser. This permits the semiconductor laser to be integrated with other components on a single semiconductor substrate, if desired, without requiring that the laser beam be emitted from the tuning element. Thus, the laser can be tuned over a wide bandwidth with efficient power extraction and high wavelength selectivity.

Abstract: An optical device has a first collimator sub-assembly having a first free-space end, and a second collimator sub-assembly having a second free-space end opposing the first free-space end of the first collimator. A central housing has first and second ends and is disposed between the first and second collimator sub-assemblies. A first ring on the first collimator sub-assembly is mounted to the first end of the central housing and a second ring on the second collimator sub-assembly is mounted to the second end of the central housing.

Abstract: A method of controlling a tuneable laser that has been characterized with respect to one or more suitable laser operation points. Each operation point is determined by the manner in which the different laser sections are controlled, in order to operate the laser at a predetermined operation point. The voltage across the different laser section is determined for different operation points when controlling the laser, and the voltages across the different laser sections are held constant when the laser is in operation to maintain a predetermined operation point.