Quantum dot SOA-silicon external cavity multi-wavelength laser
A hybrid external cavity multi-wavelength laser using a QD RSOA and a silicon photonics chip is demonstrated. Four lasing modes at 2 nm spacing and less than 3 dB power non-uniformity were observed, with over 20 mW of total output power. Each lasing peak can be successfully modulated at 10 Gb/s. At 10 −9 BER, the receiver power penalty is less than 2.6 dB compared to a conventional commercial laser. An expected application is the provision of a comb laser source for WDM transmission in optical interconnection systems.
1. A semiconductor laser, comprising:
an optical port configured to provide an optical output beam comprising one or more selected optical wavelengths;
an optical cavity, in optical communication with the optical port, comprising:
a first reflector comprising a submicron waveguide at a first end of the optical cavity, said first mirror reflector comprising a first reflectivity; and
a second reflector at a second end of the optical cavity, the second reflector comprising a second reflectivity;
at least one of said first reflector and said second reflector comprises a first Sagnac loop mirror; and
a semiconductor optical gain medium in the optical cavity for amplifying light at the one or more selected wavelengths; and
a filter element in the optical cavity configured to pass light having the one or more selected optical wavelengths therethrough to the optical gain medium and reflect wavelengths not of interest away from said optical gain medium to suppress stimulated emission of those wavelengths.
2. The laser of claim 1 , wherein said first reflector comprises a broadband reflector.
3. The laser of claim 2 , wherein the first reflector comprises the first Sagnac loop mirror.
4. The laser of claim 3 , wherein the first Sagnac loop mirror comprises a directional coupler including four branches; and wherein two of the branches on one side are tied together.
5. The laser of claim 4 , wherein said first reflector is configured, whereby said first reflectivity increases with wavelength.
6. The laser of claim 4 , wherein said first reflector comprises a tunable reflector for tuning the first reflectivity, configured to be controlled by adjusting a coupling length of the directional coupler.
7. The laser of claim 1 , wherein said filter element comprises a micro-ring based filter.
8. The laser of claim 7 , wherein said filter element is configured to provide multiple pass bands, one pass band for each selected wavelength.
9. The laser of claim 7 , wherein the one or more selected wavelengths comprises only a single selected wavelength; and wherein the filter element comprises a thermally tunable filter configured for tuning one of the pass bands to include the single selected wavelength.
10. The laser of claim 7 , wherein the one or more selected wavelengths comprises only a single selected wavelength; and wherein the filter element is configured to comprise a free spectral range wider than a gain spectrum of the optical gain medium to suppress optical cavity modes other than the selected wavelength.
11. The laser of claim 1 , wherein said first reflector and said filter element both comprise submicron silicon waveguides disposed on a first silicon chip.
12. The laser of claim 11 , wherein said optical gain medium comprises a III/V semiconductor compound provided in a second silicon chip coupled to the first silicon chip.
13. The laser of claim 12 , wherein said second reflector comprises a facet on the second silicon chip.
14. The laser of claim 12 , wherein said second reflector comprises a second Sagnac loop mirror on the second silicon chip.
15. The laser of claim 11 , wherein said optical gain medium is comprised of a semiconductor optical amplifier (SOA) optically coupled to the first silicon chip.
16. The laser of claim 15 , wherein said second reflector comprises a facet of the SOA.
17. The laser of claim 16 , wherein said facet comprises an optical coating.
18. The laser of claim 16 , wherein said first reflectivity is greater than 99%.
19. The laser of claim 15 , further comprising a coupler between the first silicon chip and the SOA; and
wherein the coupler comprises a silicon waveguide with a width which tapers down, and a silicon nitride waveguide with a width which increase gradually.
20. The laser of claim 1 , further comprising a pumping source for transferring energy to the optical gain medium.