Abstract: The thermo-optic behavior of an optical path over a range of temperatures is controlled by determining a figure of merit (FoM) for the optical path and including in the path a body of NaBi(Mo1-xWxO4)2 crystalline material that enables the conditions specified by the FOM to be satisfied. The NaBi(Mo1-xWxO4)2 crystalline material is highly transparent at a wavelength of radiation propagating in the path, and has a coefficient of thermal expansion (CTE) and a refractive index n such that the CTE and dn/dT of the etalon compensate one another so as to perform frequency discrimination that is essentially temperature insensitive over the range ?T. The NaBi(Mo1-xWxO4)2 crystalline material exhibits temperature independent transmission characteristics at about room temperature and at a wavelength of about 1550 nm.

Abstract: A method of increasing the monomolecular recombination and the immunity to noise of a continuously tunable laser is disclosed. A concentration of recombination centers in the range of about 1×1016 cm?3 to about 1×1018 cm?3 in the tuning region of the laser device is achieved by doping the waveguide layer with impurity atoms, by irradiating the waveguide layer with high energy particles or by varying the growth conditions of the waveguide layer to introduce native point defects due to lattice mismatch. This way, the monomolecular recombination is increased and the radiative recombination over low current ranges is reduced. By increasing the monomolecular recombination, the immunity to noise is improved but the tuning efficiency is reduced. Nevertheless, only a minimal effect on the tuning efficiency is noted over high current ranges and, therefore, the overall tuning range is only insignificantly changed.

Abstract: The present invention provides a method and apparatus for compensating for the age induced wavelength drift in a tunable DBR. In practice, the tuning characteristic (i.e. output wavelength versus tuning current) of a tunable DBR may be characterized before and after factory aging, typically in the form of a burn-in or purge cycle. An aging vector may be constructed in accordance with the ratio of the change in the tuning characteristic associated with a second output wavelength and the change in the tuning characteristic associated with a first output wavelength as a function of the factory aging. In addition, the tuning characteristic associated with transmission at the first output wavelength may be monitored in the field.

Abstract: The present invention provides a method and apparatus for compensating for the age induced wavelength drift in a tunable DBR. In practice, the tuning characteristic (i.e. output wavelength versus tuning current) of a tunable DBR may be characterized before and after factory aging, typically in the form of a burn-in or purge cycle. An aging vector may be constructed in accordance with the ratio of the change in the tuning characteristic associated with a second output wavelength and the change in the tuning characteristic associated with a first output wavelength as a function of the factory aging. In addition, the tuning characteristic associated with transmission at the first output wavelength may be monitored in the field.

Abstract: The thermo-optic behavior of an optical path over a range of temperatures is controlled by determining a figure of merit (FoM) for the optical path and including in the path a body of NaBi(Mo1−xWxO4)2 crystalline material that enables the conditions specified by the FOM to be satisfied. The NaBi(Mo1−xWxO4)2 crystalline material is highly transparent at a wavelength of radiation propagating in the path, and has a coefficient of thermal expansion (CTE) and a refractive index n such that the CTE and dn/dT of the etalon compensate one another so as to perform frequency discrimination that is essentially temperature insensitive over the range &Dgr;T. The NaBi(Mo1−xWxO4)2 crystalline material exhibits temperature independent transmission characteristics at about room temperature and at a wavelength of about 1550 nm.

Abstract: A method of increasing the monomolecular recombination and the immunity to noise of a continuously tunable laser is disclosed. A concentration of recombination centers in the range of about 1×1016 cm−3 to about 1×1018 cm−3 in the tuning region of the laser device is achieved by doping the waveguide layer with impurity atoms, by irradiating the waveguide layer with high energy particles or by varying the growth conditions of the waveguide layer to introduce native point defects due to lattice mismatch. This way, the monomolecular recombination is increased and the radiative recombination over low current ranges is reduced. By increasing the monomolecular recombination, the immunity to noise is improved but the tuning efficiency is reduced. Nevertheless, only a minimal effect on the tuning efficiency is noted over high current ranges and, therefore, the overall tuning range is only insignificantly changed.

Abstract: A monolithically integrated light source and frequency discriminator has a section in which a single frequency optical signal is produced and a section in which the frequency is sensed. The output of the optical discriminator is connected to a controller for stabilizing the output frequency of the light source.

Abstract: A method is disclosed for frequency stabilization of an optical source, using data obtained from a frequency stabilization system based on an optical frequency discriminator to stabilize the output of a laser to a particular grid channel. The data is mathematically manipulated to double the number of channels as compared to prior art methods and allows arbitrary channel spacing about the channels.

Abstract: A method and device for obtaining a desired phase of optical characteristic of a Fabry-Perot (FP) etalon using multiple optical detectors which, while passively aligned at various positions relative to an incident light beam, detect different phases of light signal emerging from the FP etalon. An FP etalon and optical detector array constructed in accordance with the present invention may be used as a frequency discriminator in an optical system where the FP etalon optical characteristic is required to have a particular phase.

Abstract: A DFB laser with improved loss grating is disclosed. The grating contains periodically patterned first and second semiconductor layers that are embedded in semiconductor material of composition selected to provide relatively low loss for the laser radiation. The composition of the first layer is selected to provide a relatively high refractive index and loss for the laser radiation, and the composition of the second layer is selected to provide relatively low refractive index and loss for the laser radiation. The thicknesses of the first and second layers are selected such that the real part of the coupling constant .vertline..kappa.'.vertline. is less than the imaginary part of the coupling constant .vertline..kappa.".vertline.. In preferred embodiments .vertline..kappa.'.vertline..ltoreq.0.5.vertline..kappa.".vertline., even.ltoreq.0.2.vertline..kappa.".vertline..

Abstract: In some applications of distributed feedback (DFB) lasers, it is important that the coupling constant .kappa. be closely controlled. This is not easily achieved, frequently resulting in low yield of acceptable devices. I have discovered that variations in .kappa. can be reduced if the DFB laser is designed such that the thickness t.sub.s of a spacer layer (between the active layer and the Bragg grating) is within about .+-.10% of the value t.sub.o /(1-.alpha.), where t.sub.o is the modal decay length, and .alpha. is a parameter which characterizes the fractional variation of t.sub.o with fractional changes in layer thickness.

Abstract: We have discovered that the yield of DFB lasers suitable, e.g., for use in AM CATV systems can be substantially increased if the lasers have a back facet with a higher reflectivity (>80%, preferably >90%) HR coating thereon than is conventional (e.g., .about.65%). Exemplary currently preferred embodiments of the invention comprise a three-pair stack of .lambda./4 yttrium-stablized zirconia/Si having about 95% reflectivity.

Abstract: A laser (15) is mounted on a planar surface of a monocrystalline silicon mounting member (12). A spherical lens (20) is mounted in a monocrystalline silicon cover member (13) which, when abutted and registered to the mounting member (12), aligns the spherical lens with the laser so that the output light can be projected along a precise predetermined path. The spherical lens (20) is mounted in a first V-shaped groove (31) which is made in the cover member by masking and etching. A second V-shaped groove intersects the first groove and defines a V-shaped edge in one side of the first groove. The spherical lens is then seated in the first V-shaped groove such that it bears against two points of the V-shaped edge and against one side wall (35) of the first V-shaped groove. A second lens (19) is mounted in the cover member in the same manner as the first lens and directs laser light from a rear facet of the laser to a mirror 30 and hence to a photodetector (21) mounted in the cover member.

Abstract: A laser (15) is mounted on a planar surface of a monocrystalline silicon mounting member (12). A spherical lens (20) is mounted in a monocrystalline silicon cover member (13) which, when abutted and registered to the mounting member (12), aligns the spherical lens with the laser so that the output light can be projected along a precise predetermined path. The spherical lens (20) is mounted in a first V-shaped groove (31) which is made in the cover member by masking and etching. A second V-shaped groove intersects the first groove and defines a V-shaped edge in one side of the first groove. The spherical lens is then seated in the first V-shaped groove such that it bears against two points of the V-shaped edge and against one side wall (35) of the first V-shaped groove. A second lens (19) is mounted in the cover member in the same manner as the first lens and directs laser light from a rear facet of the laser to a mirror 30 and hence to a photodetector (21) mounted in the cover member.

Abstract: Lasers for use in multichannel analog optical fiber communication systems (e.g., of the type contemplated for CATV) have to meet very stringent requirements, including high linearity. DFB lasers are advantageously used in such communication systems. Typically only a relatively small percentage of the nominally identical DFB lasers on a wafer meet the specifications. It has now been discovered that the likelihood that a given DFB laser will meet the requirements is substantially increased if the laser comprises means that are adapted for producing a non-uniform photon density in the laser cavity, with the density of photons being larger in the rear portion of the cavity than in the front portion, such that during operation of the laser the gain in the back portion is substantially independent of the laser current, whereas the gain in the front portion is a function of the laser current.

Abstract: A semiconductor distributed feedback laser having a grating with .lambda./4 phase shift which is produced by moving the left and right sections of the grating with respect to each other in a direction perpendicular to the longitudinal axis of the active region.

Abstract: A laser (24) is mounted in predetermined alignment with a monocrystalline mounting member (11) by defining in the mounting member a reference surface (18) that is displaced from a second surface (19). Solder (29) is placed on a second surface such that in its solid form its length and width each significantly exceeds its height. The laser is bonded to the reference surface such that part of the laser overlies the solder and is separated from the solder by a small gap (30). Next, the solder is melted to cause it to gather on the second surface sufficiently to contact an under surface (31) of the laser. The solder is then cooled such that the solder bonds the laser to the silicon mounting member.

Abstract: A hybrid laser arrangement is disclosed which is capable of providing an essentially uniform FM response and a relatively narrow linewidth signal, suitable for FM applications. The uniform FM response is obtained by inducing inhomogeneous linewidth enhancement through control of the bias currents applied to separate gain sections of a two-electrode Fabry-Perot device. Coupling of the two-electrode device to a narrowband resonant optical reflector provides for an extremely narrow signal linewidth.

Abstract: There are disclosed methods and apparatuses for the assembling of parts using capacitive sensing, both for controlling the closure or "homing" phase of the assembly process and for acquiring one or more of the parts prior to that phase. Assembling of semiconductor parts to essentially two-dimensional and three-dimensional packages, the insertion of a peg in a hole, and an application to tape-automated-bonding (TAB) technology are all described, as are various representations of the resulting capacitive data. Included are the uses of scheduling and optical sensing to supplement capacitive sensing in the methods and apparatuses.

Abstract: A method for aligning an opto-electronic device such as a semiconductor laser to a waveguide on a substrate is disclosed. The method comprises placing the device onto the substrate such that it is in rough alignment with the waveguide, optically pumping the device such that the device emits electromagnetic radiation, with some of the emitted radiation being coupled into the waveguide and detected by appropriate means. If indicated by the detector signal, the position of the device is then adjusted until the desired degree of coupling is attained, whereupon the device is mechanically secured to the substrate and appropriate electrical connections made between device and substrate. Devices useful in the practice of the method typically comprise a window in their top metallization layer.