Abstract: An integrated semiconductor device comprising a laser on a substrate, the laser having an active layer and a current-induced grating, such as a current-injection complex-coupled grating, within a laser cavity producing a single-mode output light signal at high data rates (>622 Mb/sec) in isolator-free operation. The grating has a coupling strength product ?L greater than 3, where ? is the coupling coefficient and L is the length of the laser cavity. In certain embodiments, the laser is a distributed feedback (DFB) laser that emits light at a wavelength of about 1.5 ?m. The strong current-induced grating prevents mode hopping between multiple degenerate Bragg modes. The laser is also characterized by excellent immunity from optical feedback, and can be operated without an isolator at high data rates.

Abstract: An avalanche photodiode (APD) includes an absorption layer above the multiplication layer, where the thickness of the multiplication layer is defined through a growth process. The APD can also have a third-terminal, or peripheral ring terminal, for collecting charge carriers generated outside the optically-active region of the device. Undesirable dark current can thus be better managed during the life of the device. The three-terminal design may also be utilized in other photodetectors, including PIN diodes.

Abstract: A semiconductor pump laser comprises a ridge waveguide electro-optical structure, which converts a ridge injection current into light and an integrated wavelength selective facet reflector. This reflector controls the longitudinal modal operation of the pump laser. Specifically, the reflector comprises a first reflective structure for reflecting light to return through the ridge waveguide electro-optical structure. A second reflective structure provides wavelength-selective reflectivity when operating in combination with the first reflective structure. In other words, the phase of light reflected from the first and second reflective structures is such that the net reflectivity of the facet is wavelength selective, or favors certain wavelengths over other wavelengths.

Abstract: An integrated semiconductor device comprising a laser on a substrate, the laser having an active layer and a current-induced grating, such as a current-injection complex-coupled grating, within a laser cavity producing a single-mode output light signal at high data rates (>622 Mb/sec) in isolator-free operation. The grating has a coupling strength product &kgr;L greater than 3, where &kgr; is the coupling coefficient and L is the length of the laser cavity. In certain embodiments, the laser is a distributed feedback (DFB) laser that emits light at a wavelength of about 1.5 &mgr;m. The strong current-induced grating prevents mode hopping between multiple degenerate Bragg modes. The laser is also characterized by excellent immunity from optical feedback, and can be operated without an isolator at high data rates.

Abstract: An integrated semiconductor device comprising a wavelength-tunable laser, such as a distributed Bragg reflector (DBR) laser, where the laser has a gain section that includes an active layer, and a grating section that includes an active layer and a current-induced grating. A first electrical contact is provided over the gain section to supply current to the gain section and control the output power of the light, and a second electrical contact is provided over the grating section to supply current to the grating section and control the wavelength of the emitted light. The current-induced grating of the present device causes gain in the active layer of the laser to be modulated spatially in the direction of light propagation, thus resulting in only one of the degenerate Bragg modes to oscillate. As the degeneracy of the Bragg modes is broken by current-injection, and not facet reflection, substantially continuous wavelength tuning is possible without the deleterious phenomenon of “mode hopping.

Abstract: A laser pump module has a ridge waveguide chip with a ridge width that is greater than 4 micrometers (&mgr;m). This is a relatively wide ridge for this class of laser chips. Specifically, especially for signal lasers, narrow ridge widths are used in order to control lateral and transverse mode shape and size. In the present invention, however, where a chip is used for pump applications, a wider ridge is used to increase the laser effective gain volume and decrease the loss associated with the lowest order transverse mode to thus maximize the useful power and light that is coupled into the fiber pigtail.

Abstract: An integrated electroabsorption modulated laser (EML) device includes a distributed feedback (DFB) laser and modulator. The DFB laser includes an active layer and a complex index grating. The modulator includes an active layer. The EML device includes a first electrical contact over the DFB laser and a second electrical contact over the modulator. The EML device includes a stop etch layer above the active layer of both the DFB laser and the modulator. An electroabsorption modulated partial grating laser (EMPGL) device includes a distributed feedback (DFB) laser, an amplifier and a modulator. An ion implantation region in the EML/EMPGL devices provides electrical isolation between the DFB laser/amplifier and the modulator.

Abstract: A laser pump module has a ridge waveguide chip with a ridge width that is flared in the direction of the rear facet. Such a ridge profile yields a number of advantages depending on the specific implementation. The resulting increase in area of the rear facet, spreads heat, to improve device performance and avoid catastrophic optical mirror damage (COD). It can also lower the power density for the same output intensity. Further, it contributes to the single lateral mode property, acting as a mode filter. Higher order modes suffer higher losses and thus, tending to contribute to their attenuation—with less light fed back into the cavity from the rear facet, the laser device as a whole has reduced outside feedback sensitivity. Thus, in the implementation as a pump laser, less light at the signal wavelength returns to be amplified in a majority of the pump's ridge waveguide cavity.

Abstract: A feedback controlled laser diode communication device is disclosed that, as is common, has a laser diode that is modulated in response to an input signal to generate an optical signal, encoding the input signal. Spatially variable passband filter material, however, is arranged to receive at least a portion of the optical signal generated by the laser diode, preferably from the rear facet, and at least one detector is used to detect the thus filtered optical signal. Control circuitry then controls a wavelength of the laser diode based upon the response of the detector(s) to thus provide feedback control. As such, the device is particularly applicable to maintaining the tight channel spacings found in wavelength division multiplexed systems.

Abstract: An electro-optical, ridge-waveguide device and method for its fabrication utilizes a polyimide ridge-protection layer, which provides good ridge protection/planarization while minimizing parasitic capacitance. A silicon oxide interlayer is used between a metal contact layer and the polyimide. This interlayer facilitates the adhesion between the metal contact layer and the underlying device since good adhesion can be obtained between the silicon oxide layer and the polyimide layer and between the metal layer and silicon oxide layer. Preferably, the polyimide is roughened to increase the surface area contact between the polyimide layer and silicon oxide layer to further increase adhesion and thus the pull-off force required to separate the metal contact layer from the device. While such roughening can be achieved through plasma etching, in a preferred embodiment, the polyimide layer is roughened by patterned etching.

Abstract: A kink suppression technique is disclosed in which optical characteristics of a distributed feedback laser diode's resonant cavity are controlled to preferentially prevent establishment of higher order lateral modes. This results in increased kink powers and thus the useful power range of the device. Specifically, an optical layer, preferably silicon or titanium, is disposed along the optical axis, on the etched upper cladding layer, and on both sides of the ridge.

Abstract: A solution for implementing gratings with optical sources where polarization-maintaining fiber is required or desirable utilizes polarization-maintaining fiber between the grating and the optical source. The grating, however, is actually written in regular, or non-polarization-maintaining fiber. The polarization-maintaining fiber is spliced to the non-PM fiber. Since this splice exists in the commercial components, it can be performed in laboratory conditions.

Abstract: A laser diode pump for fiber amplifiers, such as erbium-doped fiber amplifiers (EDFAs), reduces spurious reflections in the signal frequencies by providing a laser pump system that is dissipative at these signal frequencies. Reflections from the pump system are reduced, or eliminated by using an output facet that is currently coated to be reflective at pump frequencies, but anti-reflective, or transmissive, at the signal frequencies. In one embodiment, material layers of aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2) are used.

Abstract: An improved fiber endface shape for increasing coupling of optical power from a source into fiber and its manufacture are disclosed. The inventive tip comprises a cleaved end surface that is preferably substantially orthogonal to the fiber's axis and a first and second polished, angled surfaces intersecting the end surface. Break-lines between the angled surfaces and the end surface fall near an edge of a cladding-core interface and preferably outside that interface when the fiber and transmitted light are such that a substantial portion of the light is transmitted in the cladding. A spatial intensity profile of light exiting from the tip is detected during manufacture and is used to monitor the polishing of the angled surfaces. Tests have shown that the inventive tip achieves the coupling efficiency associated with the double-angled wedge-shaped fiber tips while maintaining much of the ease of manufacture associated with the single-angle wedge tips.