Tunable laser with integrated wavelength reference
In the prior art, tunable lasers utilizing silicon-based tunable ring filters and III-V semiconductor-based gain regions required the heterogeneous integration of independently formed silicon and III-V semiconductor based optical elements, resulting in large optical devices requiring a complex manufacturing process (e.g., airtight packaging to couple the devices formed on different substrates, precise alignment for the elements, etc.). Embodiments of the invention eliminate the need for bulk optical elements and hermetic packaging, via the use of hybridized III-V/silicon gain regions and silicon optical components, such as silicon wavelength filters and stabilized wavelength references, thereby reducing the size and manufacturing complexity of tunable lasing devices.
1. A tunable laser, comprising:
a silicon substrate defining a waveguide, the waveguide being configured to propagate light,
the silicon substrate including a gain region configured to amplify light propagating through the waveguide and including a silicon material and a III-V semiconductor material,
the silicon substrate further including a passive region,
the passive region including a tunable ring filter configured to filter a wavelength of light propagating through the waveguide,
the passive region further including an output coupler configured to allow amplified, wavelength-filtered light to exit the waveguide, the output coupler further configured to extract a portion of light from the amplified, wavelength-filtered light in the waveguide;
the passive region further including a stabilized wavelength reference positioned exterior to the waveguide and configured to receive the extracted portion of light; and
a heating element disposed proximate the stabilized wavelength reference, the heating element configured to stabilize a temperature of the stabilized wavelength reference thereby to stabilize the wavelength filtered by the tunable ring filter.
2. The tunable laser of claim 1 , wherein the stabilized wavelength reference comprises at least one of an etalon, an interference filter, or an optical grating.
3. The tunable laser of claim 1 , wherein the waveguide forms a laser cavity that includes the gain region and the tunable ring filter, and extends to the output coupler.
4. The tunable laser of claim 3 , wherein the waveguide further extends through a phase control region formed in a passive region of the silicon substrate, the phase control region being configured to adjust resonant cavity modes of the laser cavity.
5. The tunable laser of claim 4 , wherein the phase control region is positioned along the waveguide between the gain region and the output coupler.
6. The tunable laser of claim 3 , wherein light is bi-directional within the laser cavity.
7. The tunable laser of claim 1 , wherein the stabilized wavelength reference includes a temperature sensor.
8. The tunable laser of claim 7 , wherein the temperature sensor is a resistive thermal device.