Dissipating heat from an active region of an optical device
A device, such as an electroabsorption modulator, can modulate a light intensity by controllably absorbing a selectable fraction of the light. The device can include a substrate. A waveguide positioned on the substrate can guide light. An active region positioned on the waveguide can receive guided light from the waveguide, absorb a fraction of the received light, and return a complementary fraction of the received light to the waveguide. Such absorption produces heat, mostly at an input portion of the active region. The input portion of the active region can be thermally coupled to the substrate, which can dissipate heat from the input portion, and can help avoid thermal runaway of the device. The active region can be thermally isolated from the substrate away from the input portion, which can maintain a relatively low thermal mass for the active region, and can increase efficiency when heating the active region.
1. An optical device, comprising:
a waveguide layer comprising a waveguide to guide light;
an active region comprising a coupled portion to couple light in the waveguide; and
one or more electrodes to provide a first electric field in the coupled portion of the active region and provide a second electric field in portions of the active region away from the coupled portion, the first electric field of the coupled portion being lower than the second electric field to compensate from increased heating at the coupled portion due to coupling of light from the waveguide layer to the active region.
2. The optical device of claim 1 , wherein the first electric field is lower than the second electric field due to ions implanted in the coupled portion of the active region.
3. The optical device of claim 2 , wherein the ions reduce a doping of active material of the active region.
4. The optical device of claim 2 , wherein the ions comprise fluorine ions.
5. The optical device of claim 1 , wherein the optical device comprises an oxide layer between the waveguide layer and a substrate layer of the optical device.
6. The optical device of claim 1 , wherein the portions of the active region away from the coupled portion are outside the coupled portion.
7. The optical device of claim 1 , further comprising:
a heater configured to heat the active region.
8. The optical device of claim 7 , further comprising:
control circuitry to control the heater to heat the active region.
9. The optical device of claim 1 , wherein the optical device further comprises control circuitry to control a supply of voltage to the one or more electrodes.
10. The optical device of claim 1 , wherein the active region comprises a III-V semiconductor material having an absorption spectrum that varies in response to heat from a heater.
11. The optical device of claim 10 , wherein an absorption of the 111 -V semiconductor material increases with increasing temperature.
12. The optical device of claim 1 , wherein the waveguide tapers to a narrowed portion at a first taper and widens from the narrowed portion at a second taper.
13. The optical device of claim 12 , wherein the active region is parallel to and adjacent the narrowed portion.
14. The optical device of claim 13 , wherein the active region extends beyond the narrowed portion to partially overlap with the first taper.
15. The optical device of claim 1 , wherein at least one of the one or more electrodes is segmented proximate the coupled portion of the active region.
16. The optical device of claim 1 , further comprising at least one silicon rib oriented parallel to the active region and positioned between the active region and an etched portion of a substrate layer of the optical device, the at least one silicon rib having a cross-sectional size that is smaller than a wavelength of the guided light.
17. A method, comprising:
guiding light in a waveguide of a waveguide layer of an optical device;
coupling light to a coupled portion of an active region of the optical device;
providing, using one or more electrodes of the optical device, a first electric field and a second electric field to the active region, the first electric field provided to the coupled portion of the active region, the second electric field provided to portions of the active region away from the coupled portion, the first electric field of the coupled portion being lower than the second electric field to compensate from increased heating at the coupled portion due to coupling of light from the waveguide layer to the active region.
18. The method of claim 17 , wherein the first electric field is lower than the second electric field due to ions implanted in the coupled portion of the active region.
19. The method of claim 18 , wherein the ions reduce a doping of active material of the active region.
20. The method of claim 18 , wherein the ions comprise fluorine ions.