Hybrid integration of a wavelength selectable laser source and optical amplifier/modulator

Abstract

A hybrid integrated optical transmitter comprising a wavelength selectable laser (WSL) source coupled to an optical amplifier/modulator has been realized. Disposed between the optical combiner and the optical amplifier/modulator is an “optical isolator.” The optical isolator includes at least a Faraday rotator and, either solely or in combination with a single polarizer and/or half-wave plate is used to selectively rotate and pass polarized light egressing from the wavelength selectable laser source. Optical isolation is achieved by the egressing radiation from and back reflections incident on the laser source being at two mutually exclusive orthogonal polarization states or by the reflections being totally extinguished. Advantageously, the laser source is unresponsive to orthogonally polarized light, and hence any unwanted back reflections do not substantially affect the operating characteristics of the laser(s). Optical isolation may be further improved, however, with the use of an additional polarizer positioned in front of the Faraday rotator to totally extinguish the polarized back reflections. Preferably, a latching Faraday rotator is used. As such, permanent magnets are not needed to maintain the latching Faraday rotator in its saturated state, and substantially reduces cost, size and complexity of the transmitter package. The wavelength selectable laser source is integrated on a single substrate with an optical combiner that directs the radiation to the optical amplifier/modulator, which is integrated on a second substrate. Alternatively, the laser source and optical combiner may be integrated on different substrates.