Multi-wavelength semiconductor comb lasers
Examples disclosed herein relate to multi-wavelength semiconductor comb lasers. In some examples disclosed herein, a multi-wavelength semiconductor comb laser may include a waveguide included in an upper silicon layer of a silicon-on-insulator (SOI) substrate. The comb laser may include a quantum dot (QD) active gain region above the SOI substrate defining an active section in a laser cavity of the comb laser and a dispersion tuning section included in the laser cavity to tune total cavity dispersion of the comb laser.
1. A multi-wavelength semiconductor comb laser, comprising:
a silicon-on-insulator (S 01 ) substrate comprising a lower silicon layer, a buried silicon oxide layer (SiO 2 ), and an upper silicon layer;
a waveguide included in the upper silicon layer of the SOI substrate;
a quantum dot (QD) active gain region above the SOI substrate defining an active section in a laser cavity of the comb laser; and
a dispersion tuning section to tune total cavity dispersion of the comb laser, the dispersion tuning section comprising a vertical slot waveguide, the vertical slot waveguide comprising a lower rail formed in the upper silicon layer of the SOI substrate having a plurality of widths along a length of the lower rail, a plurality of airgaps, a slot region formed in a dielectric layer above the lower rail, and an upper rail formed in a cladding layer above the dielectric layer,
wherein the dispersion tuning section is configured to adjust one or more of: a depth of one or more of the plurality of airgaps, one or more of the plurality of widths of the lower rail, a thickness of the dielectric layer, or a thickness of the cladding layer to tune total cavity dispersion of the comb laser, and
wherein the dispersion tuning section is configured to enable tuning of total cavity dispersion of the comb laser for broad comb operation in a wavelength range of 1.3 μm to 1.6 μm.
2. The multi-wavelength semiconductor comb laser of claim 1 , comprising:
a first mirror and a second mirror at opposite ends of the comb laser along a length of the comb laser, the area between the first mirror and the second mirror defining the laser cavity of the comb laser.
3. The multi-wavelength semiconductor comb laser of claim 2 , wherein the dispersion tuning section is included in the laser cavity between the first mirror and the second mirror.
4. The multi-wavelength semiconductor comb laser of claim 1 , wherein the cladding layer comprises a III-V material.
5. The multi-wavelength semiconductor comb laser of claim 1 , wherein the cladding layer comprises epitaxial silicon.
6. The multi-wavelength semiconductor comb laser of claim 5 , wherein the comb laser comprises:
an oxide layer formed above the dielectric layer and below the cladding layer.
7. The multi-wavelength semiconductor comb laser of claim 1 , comprising a saturable absorber.
8. The multi-wavelength semiconductor comb laser of claim 1 , wherein the dispersion tuning section is included in a passive section of the laser cavity.
9. The multi-wavelength semiconductor comb laser of claim 1 , comprising:
a second dispersion tuning section to tune total cavity dispersion of the comb laser, wherein the dispersion tuning section comprises a first pair of coupled rings at a first end of the laser cavity and the second dispersion tuning section comprises a second pair of coupled rings at a second end of the laser cavity opposite to the first end.
10. A multi-wavelength semiconductor comb laser, comprising:
a waveguide included in an upper silicon layer of a silicon on insulator (S 01 ) substrate, the SOI substrate comprising a lower silicon layer, a buried silicon oxide layer (SiO 2 ), and the upper silicon layer;
a first mirror and a second mirror at opposite ends of the comb laser defining a laser cavity along a length of the comb laser;
a quantum dot (QD) III-V layer above the SOI substrate defining an active section in the laser cavity; and
a dispersion tuning section included in the active section of the laser cavity to tune total cavity dispersion of the comb laser, the dispersion tuning section comprising a vertical slot waveguide, the vertical slot waveguide comprising a lower rail formed in the upper silicon layer of the SOI substrate having a plurality of widths along a length of the lower rail, a plurality of airgaps, a slot region formed in a dielectric layer above the lower rail, and an upper rail formed in a cladding layer above the dielectric layer,
wherein the dispersion tuning section is configured to adjust one or more of: a depth of one or more of the plurality of airgaps, one or more of the plurality of widths of the lower rail, a thickness of the dielectric layer, or a thickness of the cladding layer to tune total cavity dispersion of the comb laser, and
wherein the dispersion tuning section is configured to enable tuning of total cavity dispersion of the comb laser for broad comb operation in a wavelength range of 1.3 μm to 1.6 μm.
11. The multi-wavelength semiconductor comb laser of claim 10 , wherein the vertical slot waveguide comprises:
an upper rail formed in III-V layer stack above the dielectric layer.
12. The multi-wavelength semiconductor comb laser of claim 11 , wherein the III-V layer stack comprises:
a lower cladding layer;
the QD III-V layer above the lower cladding layer; and
an upper cladding layer above the QD III-V layer.