Abstract: A process for fabricating a waveguide with a desired tapered profile is disclosed. The waveguide has a first section with a first height and a second section with a second height. The first height is greater than the second height. The waveguide height tapers from the first height to the second height. The waveguide is a compound semiconductor material and is formed using selective area growth. In selective area growth, a dielectric mask is formed on a substrate. The dimensions of the dielectric mask are selected to provide a waveguide with the desired dimensions. The compound semiconductor material is deposited on the substrate using chemical vapor deposition. The dielectric mask affects the rate at which the compound material is deposited in areas of the substrate proximate to the mask. Therefore, the profile of the waveguide formed using the selected mask dimensions is modeled and compared with the desired profile.

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 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 voltage applied to the composite reflector induces a quantum confined stark effect, thereby allowing the wavelength to be altered. In one embodiment, the current drive to the active region and the shape of the first waveguide (e.g., a raised-sine function) are mutually adapted so that N longitudinal modes have essentially the same threshold gain and so that the DFB region spanned by the first waveguide is segmented into N zones, each zone providing optical feedback at a different wavelength corresponding to a different longitudinal mode.

Abstract: In a WDM fiber-optic network, a unique laser transmitter enables signals to be routed at three hierarchical levels: at one level discrimination among signal paths is based on N WDM wavelength channels, at another level discrimination is based on m AM subcarrier frequency channels, and at a third level discrimination is based on n FM subcarrier frequency channels. Thus, a total of Nmn distinguishable optical channels can be accommodated and a like number of users served. The laser transmitter comprises a broadband, tunable semiconductor laser which includes an intracavity, integrated composite reflector to which a tuning voltage and a FM dither signal are applied, an intracavity gain section to which drive current is applied, and an extracavity, integrated electroabsorption modulator to which an information (e.g., data, voice, video) signal and an AM dither signal are applied.

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 a quantum confined stark effect, thereby allowing the center wavelength to be altered. A pre-chirp signal applied the composite reflector reduces signal distortion in fiber optic systems.

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. A dither signal applied the composite reflector broadens the spectrum of the laser output, thereby reducing SBS in fiber optic systems.

Abstract: A strained layer superlattice comprising Ge.sub.x Si.sub.1-x layers interleaved with Si layers is an excellent photodetector at infrared wavelengths due to the large shift in bandgap caused by the strain in the superlattice.