Abstract: A tunable laser with multiple in-line sections including sampled gratings generally includes a semiconductor laser body with a plurality of in-line laser sections configured to be driven independently to generate laser light at a wavelength within a different respective wavelength range. Sampled gratings in the respective in-line sections have the same grating period and a different sampling period to produce the different wavelengths. The wavelength of the light generated in the respective laser sections may be tuned, in response to a temperature change, to a channel wavelength within the respective wavelength range. By selectively generating light in one or more of the laser sections, one or more channel wavelengths may be selected for lasing and transmission. By using sampled gratings with the same grating period in the multiple in-line sections, the multiple section tunable laser may be fabricated more easily.

Abstract: A parallel cavity tunable laser generally includes a semiconductor laser body defining a plurality of parallel laser cavities with a common output. Each of the parallel laser cavities is configured to be driven independently to generate laser light at a wavelength within a different respective wavelength range. The wavelength of the light generated in each of the laser cavities may be tuned, in response to a temperature change, to a channel wavelength within the respective wavelength range. The laser light generated in each selected one of the laser cavities is emitted from the common output at a front facet of the laser body. By selectively generating light in one or more of the laser cavities, one or more channel wavelengths may be selected for lasing and transmission.

Abstract: A two-section semiconductor laser includes a gain section and a modulation-independent grating section to reduce chirp. The modulation-independent grating section includes a diffraction grating for reflecting light and forms a laser cavity with the gain section for lasing at a wavelength or range of wavelengths reflected by the diffraction grating. The gain section of the semiconductor laser includes a gain electrode for driving the gain section with at least a modulated RF signal and the grating section includes a grating electrode for driving the grating section with a DC bias current independent of the modulation of the gain section. The semiconductor laser may thus be directly modulated with the modulated RF signal without the modulation significantly affecting the index of refraction in the diffraction grating, thereby reducing chirp.

Abstract: A dual testing system and method is used to perform both optical power and wavelength measurements on laser light emitted from a laser diode, such as a chip-on-submount (COS) laser diode or a laser diode in a bar laser. A testing fixture may be used to facilitate both measurements by simultaneously detecting the light for performing a first test including the optical power measurement(s) and reflecting the light for performing a second test including the wavelength measurement(s). The testing fixture may include an angled photodetector and an optical coupling system such as a collimating lens, a focal lens and an optical waveguide. The testing fixture may be electrically connected to an optical power testing module, such as a light-current-voltage (LIV) testing module, for performing the optical power measurement(s) and may be optically coupled to a wavelength measurement module, such as an optical spectrum analyzer (OSA) for performing the wavelength measurement(s).

Abstract: Individual channels of a multiplexed laser array in a multi-channel optical transmitter are monitored at an output of an optical multiplexer. The monitoring may be used to confirm proper operation of each of the channels in the multiplexed laser array and/or to perform wavelength locking on each of the channels. Monitoring at the output of the optical multiplexer avoids the use of multiple photodetectors coupled directly to multiple lasers in the multiplexed laser array. The multiplexed laser array generally includes a plurality of laser emitters optically coupled to an optical multiplexer such as an arrayed waveguide grating (AWG). An optical transmitter with a monitored multiplexed laser array may be used, for example, in an optical line terminal (OLT) in a wavelength division multiplexed (WDM) passive optical network (PON) or in any other type of WDM optical communication system capable of transmitting optical signals on multiple channel wavelengths.

Abstract: A parallel cavity tunable laser generally includes a semiconductor laser body defining a plurality of parallel laser cavities with a common output. Each of the parallel laser cavities is configured to be driven independently to generate laser light at a wavelength within a different respective wavelength range. The wavelength of the light generated in each of the laser cavities may be tuned, in response to a temperature change, to a channel wavelength within the respective wavelength range. The laser light generated in each selected one of the laser cavities is emitted from the common output at a front facet of the laser body. By selectively generating light in one or more of the laser cavities, one or more channel wavelengths may be selected for lasing and transmission.

Abstract: A dual testing system and method is used to perform both optical power and wavelength measurements on laser light emitted from a laser diode, such as a chip-on-submount (COS) laser diode or a laser diode in a bar laser. A testing fixture may be used to facilitate both measurements by simultaneously detecting the light for performing a first test including the optical power measurement(s) and reflecting the light for performing a second test including the wavelength measurement(s). The testing fixture may include an angled photodetector and an optical coupling system such as a collimating lens, a focal lens and an optical waveguide. The testing fixture may be electrically connected to an optical power testing module, such as a light-current-voltage (LIV) testing module, for performing the optical power measurement(s) and may be optically coupled to a wavelength measurement module, such as an optical spectrum analyzer (OSA) for performing the wavelength measurement(s).

Abstract: A two-section semiconductor laser includes a gain section and a modulation-independent grating section to reduce chirp. The modulation-independent grating section includes a diffraction grating for reflecting light and forms a laser cavity with the gain section for lasing at a wavelength or range of wavelengths reflected by the diffraction grating. The gain section of the semiconductor laser includes a gain electrode for driving the gain section with at least a modulated RF signal and the grating section includes a grating electrode for driving the grating section with a DC bias current independent of the modulation of the gain section. The semiconductor laser may thus be directly modulated with the modulated RF signal without the modulation significantly affecting the index of refraction in the diffraction grating, thereby reducing chirp.

Abstract: An improved scribe etch process for semiconductor laser chip manufacturing is provided. A method to etch a scribe line on a semiconductor wafer generally includes: applying a mask layer to a surface of the wafer; photolithographically opening a window in the mask layer along the scribe line; etching a trench in the wafer using a chemical etchant that operates on the wafer through the window opening, wherein the chemical etchant selectively etches through crystal planes of the wafer to generate a V-groove profile associated with the trench; and cleaving the wafer along the etched trench associated with the scribe line through application of a force to one or more regions of the wafer.

Abstract: A semiconductor laser diode with integrated heating generally includes a lasing region and a heating region integrated into the same semiconductor structure or chip. The lasing region and the heating region include first and second portions, respectively, of the semiconductor layers forming the semiconductor structure and include first and second portions, respectively, of the active regions formed by the semiconductor layers. Separate laser and heater electrodes are electrically connected to the respective lasing and heating regions for driving the respective lasing and heating regions with drive currents. The heating region may thus be driven independently from the lasing region, and heat may be conducted through the semiconductor layers from the heating region to the lasing region allowing the temperature to be controlled more efficiently.

Abstract: A semiconductor laser diode with integrated heating generally includes a lasing region and a heating region integrated into the same semiconductor structure or chip. The lasing region and the heating region include first and second portions, respectively, of the semiconductor layers forming the semiconductor structure and include first and second portions, respectively, of the active regions formed by the semiconductor layers. Separate laser and heater electrodes are electrically connected to the respective lasing and heating regions for driving the respective lasing and heating regions with drive currents. The heating region may thus be driven independently from the lasing region, and heat may be conducted through the semiconductor layers from the heating region to the lasing region allowing the temperature to be controlled more efficiently.

Abstract: Individual channels of a multiplexed laser array in a multi-channel optical transmitter are monitored at an output of an optical multiplexer. The monitoring may be used to confirm proper operation of each of the channels in the multiplexed laser array and/or to perform wavelength locking on each of the channels. Monitoring at the output of the optical multiplexer avoids the use of multiple photodetectors coupled directly to multiple lasers in the multiplexed laser array. The multiplexed laser array generally includes a plurality of laser emitters optically coupled to an optical multiplexer such as an arrayed waveguide grating (AWG). An optical transmitter with a monitored multiplexed laser array may be used, for example, in an optical line terminal (OLT) in a wavelength division multiplexed (WDM) passive optical network (PON) or in any other type of WDM optical communication system capable of transmitting optical signals on multiple channel wavelengths.

Abstract: A tunable laser with multiple in-line sections generally includes a semiconductor laser body with a plurality of in-line laser sections each configured to be driven independently to generate laser light at a wavelength within a different respective wavelength range. The wavelength of the light generated in each of the laser sections may be tuned, in response to a temperature change, to a channel wavelength within the respective wavelength range. The laser light generated in each selected one of the laser sections is emitted from a front facet of the laser body. By selectively generating light in one or more of the laser sections, one or more channel wavelengths may be selected for lasing and transmission. The tunable laser with multiple in-line sections may be used, for example, in a tunable transmitter in an optical networking unit (ONU) in a WDM passive optical network (PON) to select a transmission channel wavelength.

Abstract: An improved scribe etch process for semiconductor laser chip manufacturing is provided. A method to etch a scribe line on a semiconductor wafer generally includes: applying a mask layer to a surface of the wafer; photolithographically opening a window in the mask layer along the scribe line; etching a trench in the wafer using a chemical etchant that operates on the wafer through the window opening, wherein the chemical etchant selectively etches through crystal planes of the wafer to generate a V-groove profile associated with the trench; and cleaving the wafer along the etched trench associated with the scribe line through application of a force to one or more regions of the wafer.

Abstract: A tunable laser with multiple in-line sections including sampled gratings generally includes a semiconductor laser body with a plurality of in-line laser sections configured to be driven independently to generate laser light at a wavelength within a different respective wavelength range. Sampled gratings in the respective in-line sections have the same grating period and a different sampling period to produce the different wavelengths. The wavelength of the light generated in the respective laser sections may be tuned, in response to a temperature change, to a channel wavelength within the respective wavelength range. By selectively generating light in one or more of the laser sections, one or more channel wavelengths may be selected for lasing and transmission. By using sampled gratings with the same grating period in the multiple in-line sections, the multiple section tunable laser may be fabricated more easily.

Abstract: A directly modulated distributed feedback (DFB) laser with improved optical field uniformity and mode stability may include a laser cavity and a distributed reflector and/or external reflectors. The distributed reflector may be a Bragg grating and may extend asymmetrically over a only portion of the laser cavity. The external reflectors may themselves be distributed Bragg reflectors and may have unequal reflectances. Optical field uniformity may be improved by adjusting the length and/or position of the distributed reflector in the laser cavity. Optical field uniformity may be improved by adjusting a coupling strength parameter, which is a function of a coupling coefficient, ?, and the length of the distributed reflector.

Abstract: A directly modulated distributed feedback (DFB) laser with improved optical field uniformity and mode stability may include a laser cavity and a distributed reflector and/or external reflectors. The distributed reflector may be a Bragg grating and may extend asymmetrically over a only portion of the laser cavity. The external reflectors may themselves be distributed Bragg reflectors and may have unequal reflectances. Optical field uniformity may be improved by adjusting the length and/or position of the distributed reflector in the laser cavity. Optical field uniformity may be improved by adjusting a coupling strength parameter, which is a function of a coupling coefficient, ?, and the length of the distributed reflector.

Abstract: Methods for fabricating a VCSEL having current confinement, the VCSEL having a substrate, a semiconductor active region, and a bottom mirror disposed between the substrate and the active region. A first top spacer layer is epitaxially grown on the active region, the first top spacer layer comprising a current-spreading buffer layer disposed on the active region, a current-confinement layer disposed on the buffer layer, and a current-spreading platform layer disposed on the current-confinement layer, wherein the combined thickness of the platform and current-confinement layers is less than the thickness of the buffer layer. A current-confinement structure having an annular region of enhanced resistivity and a central aperture of comparatively lower resistivity is formed in the current-confinement layer using ion implantation. Subsequently, epitaxial regrowth is performed to form a second top spacer layer on the platform layer, said second top spacer layer comprising a top current-spreading layer.

Abstract: A surface-emitting laser, such as a VCSEL, for generating single-transverse mode laser light at a lasing wavelength, has a first mirror and a second mirror positioned so as to define a laser cavity therebetween, and a semiconductor active region disposed between the first and second mirrors for amplifying, by stimulated emission, light in the laser cavity at the lasing wavelength. An annular antiguide structure is disposed within the laser cavity and between the active region and one of the first and second mirrors, the annular antiguide structure comprising an antiguide material and having a central opening, the central opening comprising a second material having an index of refraction for light at the lasing wavelength smaller than that of the antiguide material, whereby the annular antiguide structure causes preferential antiguiding of higher order transverse lasing modes in the laser cavity.

Abstract: A multiple reflectivity band reflector (MRBR) includes a stack of dielectric layers, arranged so that the reflector has a reflectivity profile comprising a plurality of reflectivity bands, e.g. at least first and second wavelength bands with reflectivity above a lasing threshold reflectivity, separated by a third wavelength band between the first and second wavelength bands having reflectivity below the lasing threshold reflectivity. A laser having at least a first mirror and an MRBR as the second mirror has a laser cavity, at least a portion of which is defined by the first mirror and the MRBR. An active region located within the laser cavity contains a material that is capable of stimulated emission at one or more wavelengths in the first and second wavelength bands. The gain spectrum of the laser is adjusted to select one of the first and second wavelength bands, thereby providing for lasing at a wavelength within the selected wavelength band. The laser may be, e.g.