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 silicon wavelength references, thereby reducing the size and manufacturing complexity of tunable lasing devices. For example, embodiments of the invention may utilize hybridized III-V/silicon gain regions with ring filters on silicon form a tunable laser with efficient gain from the III-V region, while providing wide tunability, efficient tunability, and narrow linewidth due to the nature of the silicon rings.
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 configured to filter a wavelength of light propagating through the waveguide, the passive region including at least a portion of a laser cavity, the laser cavity arranged in a ring topography so that light propagates in a single direction within the laser cavity;
an output coupler formed in a passive region of the silicon substrate, the output coupler configured to allow amplified and filtered light to exit the waveguide, the output coupler further configured to produce optical feedback from the amplified and filtered light in the waveguide; and
a heating element disposed proximate the waveguide, the heating element configured to adjust a temperature of the passive region in response to the optical feedback thereby to adjust the wavelength of light filtered in the waveguide.
2. The tunable laser of claim 1 , wherein the passive region of the silicon substrate includes a tunable ring filter.
3. The tunable laser of claim 1 , wherein the passive region of the silicon substrate includes a plurality of cascaded tunable ring filters, each tunable ring filter having a different radius value.
4. The tunable laser of claim 3 , wherein the waveguide extends through an electroabsorption modulator configured to perform amplitude or phase modulation of light propagating within the waveguide.
5. The tunable laser of claim 4 , wherein the output coupler is positioned along the waveguide between the electroabsorption modulator and the plurality of cascaded tunable ring filters.
6. The tunable laser of claim 1 , wherein the waveguide 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.
7. The tunable laser of claim 6 , wherein the phase control region is positioned along the waveguide between the wavelength reference and the gain region.