Tunable VCSEL polarization control with intracavity subwavelength grating
AssigneeExcelitas Technologies Corp.
InventorBartley C. Johnson
Life of this patent
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Abstract
A very strong selection mechanism is provided in a tunable vertical cavity surface emitting laser (VCSEL) by manipulating the laser threshold to be different for TE and TM polarization by a employing a subwavelength grating in the laser cavity. The laser selects the polarization with the lowest threshold. The grating does not diffract and does not add loss to the cavity. It works by creating a large birefringence layer between the semiconductor and air sub-cavities of the full VCSEL. Multilayer stack calculations show that this results in a lower threshold for the TM polarization over the TE. This subwavelength grating layer, in one embodiment, replaces the AR coating on the semiconductor surface.
Claims18
A tunable vertical surface emitting laser configured to emit light at least at a wavelength (λ), comprising:
- a deflectable membrane device carrying a mirror and a half VCSEL defining an optical cavity of the laser;
- and
- a subwavelength grating formed in a material in the optical cavity, wherein the material has a refractive index (n), and wherein the subwavelength grating has a pitch (Λ) that is less than λ/n.
A method for fabricating a tunable vertical surface emitting laser configured to emit light at least at a wavelength (λ), comprising:
- forming a deflectable membrane device and a half VCSEL device defining an optical cavity of the laser;
- and
- forming a subwavelength grating into a material in the half VCSEL device, wherein the material has a refractive index (n), and wherein the subwavelength grating has a pitch (Λ) that is less than λ/n.
A tunable vertical surface emitting laser system configured to emit light at least at a wavelength (λ), comprising:
- a laser comprising a deflectable membrane device carrying a mirror and a half VCSEL defining an optical cavity of the laser and a subwavelength grating formed in a material in the optical cavity, wherein the material has a refractive index (n), and
- wherein the subwavelength grating has a pitch (Λ) that is less than λ/n;
- and
- a pump chip for optically pumping the laser.
Dependencies are inferred from the claim text.