Patent ID: 7633988

Claim:
A semiconductor optical transmitter, comprising: a common substrate; a tunable laser resonator, formed on the common substrate, for producing a light beam, such that the wavelength of the light beam is tunable over a wider wavelength range than is achievable by index tuning of the tunable laser resonator, wherein the wider wavelength range is represented by Δλ/λ>Δn/n, λ represents the wavelength of the light beam, Δλ represents the change in the wavelength of the light beam, n represents the index tuning of the laser, and Δn represents the change in the index tuning of the laser; a semiconductor Mach-Zehnder (MZ) modulator, formed on the common substrate and positioned external to the tunable laser resonator, wherein the MZ modulator includes first and second multimode interference (MMI) couplers, the first MMI coupler divides the light beam into first and second components that are directed by first and second optical waveguides to inputs of the second MMI coupler, the second MMI coupler combines the first and second components interferometrically, thereby directing the combined components to an output of the second MMI coupler, the first and second waveguides each include a first electrode for applying an electric field to modulate an optical path length of the waveguide, and at least one of the first and second waveguides includes a second electrode for applying a current to adjust a phase of the light beam; and one or more output couplers formed on the common substrate in the epitaxial structure, wherein at least one of the couplers is positioned and configured to receive the light beam output from the MZ modulator, reduce back reflections to the MZ modulator, and couple the light beam output from the MZ modulator to a following optical assembly.