Abstract: A semiconductor laser comprises two optical cavities, each comprising an optical waveguide bounded by two partially reflecting elements. The two optical waveguides are disposed on a substrate to form a substantially V-shaped geometry with substantially no cross-coupling at the open end and a predetermined cross-coupling at the closed end for achieving an optimal single-mode selectivity of the laser. The first cavity has a length such that its resonant wavelengths correspond to a set of discrete operating channels. The second cavity has a slightly different length so that only one resonant wavelength coincides with one of the resonant wavelengths of the first cavity over the operating spectral window. The lasing action occurs at the common resonant wavelength. In operation, at least a portion of the optical waveguide in each of the first and the second cavities are forward biased to provide substantially equal round-trip optical gains.

Abstract: A Q-modulated semiconductor laser comprises a ?/4-phase-shifted distributed-feedback grating. Two isolated electrodes are deposited on top of the grating, and one electrode is deposited on the back side of the laser substrate as a common ground. The first top-side electrode covers a portion of the grating including the phase-shift region, and provides an optical gain for the laser when a constant current is injected. The second top-side electrode covers the remaining portion of the grating away from the phase-shift region, which acts as a Q-modulator of the laser. An electrical signal is applied on the second electrode to change the absorption coefficient of the waveguide in the modulator section, resulting in a change in the Q-factor of the laser, and consequently the lasing threshold and output power. The integrated Q-modulated laser has advantages of high speed, high extinction ratio, low wavelength chirp and low cost.

Abstract: A Q-modulated semiconductor laser comprises an optical gain section and an electro-absorptive modulator section, separated by a vertically etched air gap acting as a partially reflecting mirror. The modulator section is placed inside an anti-resonant Fabry-Perot cavity and acts as the rear reflector of the laser. The change of the absorption coefficient in the modulator section results in a change in the Q-factor of the laser, and consequently the lasing threshold and output power. Different embodiments are disclosed, which involve a distributed feedback (DFB) laser, a Fabry-Perot laser, a distributed Bragg reflector (DBR) laser, or a wavelength switchable multi-cavity laser. The integrated Q-modulated laser has advantages of high speed, high extinction ratio, low wavelength chirp and low cost.

Abstract: A monolithically integrated wavelength switchable laser comprises three coupled Fabry-Perot cavities. The length and consequently the free spectral range of the first cavity are designed such that the resonant peaks correspond substantially to a set of discrete operating wavelengths separated by a constant channel spacing. The second cavity has a slightly different length so that only one resonant peak coincides with one of the resonant peaks of the first cavity over the spectral window of the material gain. The lasing action occurs at the common resonant wavelength. The two cavities are coupled through a third short cavity that produces a certain coupling loss and phase relationship between the first and the second cavities in order to achieve an optimal mode selectivity of the combined cavity laser. In operation, both the first and the second cavities are forward biased to provide optical gains for the laser action.

Abstract: A monolithic single-mode semiconductor laser comprises three coupled Fabry-Perot cavities in tandem, each separated by a vertically etched air gap of a size that is substantially equal to an odd-integer multiple of quarter-wavelength. The middle cavity is actively pumped to provide gains to the combined cavity laser. The other cavities are substantially transparent and act as an optical filter to select one of the longitudinal modes of the middle cavity as the lasing mode. The lengths of the two passive cavities are substantially different so that a narrow filtering function with a large free spectral range is obtained for optimal mode selectivity.