IP Library › Granted Patent US 12,388,235
Granted Patent B2
US 12,388,235 · App. 17/706,682 · Granted Aug 12, 2025

Tunable VCSEL polarization control with intracavity subwavelength grating

Inventor: Bartley C. Johnson (North Andover, MA)
Assignee: Excelitas Technologies Corp.
H01S5/18366H01S5/0281H01S5/041H01S5/068H01S5/18361H01S5/18383H01S5/18386H01S5/343
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Quick Facts
Patent No.
US 12,388,235
App. No.
17/706,682
Granted
Aug 12, 2025
Kind
B2
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.

Claims (25)

1. 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.

2. The laser of claim 1 , wherein the subwavelength grating is located on the half VCSEL.

3. The laser of claim 1 , wherein the subwavelength grating formed on a top high index layer of the half VCSEL.

4. The laser of claim 1 , wherein the half VCSEL includes a distributed Bragg reflector.

5. The laser of claim 1 , wherein the grating has a 50% duty cycle.

6. The laser of claim 1 , wherein the grating is alternating material and air.

7. The laser of claim 1 , wherein the grating is alternating InGaP and air.

8. The laser of claim 1 , wherein the grating replaces an antireflective coating on the half VCSEL.

9. 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.

10. The method of claim 9 , wherein the subwavelength grating is etched into the half VCSEL device.

11. The method of claim 9 , wherein the subwavelength grating is etched into on a top high index layer of the half VCSEL.

12. The method of claim 9 , wherein the grating has a 50% duty cycle.

13. The method of claim 9 , wherein the grating is alternating material and air.

14. The method of claim 9 , wherein the grating is alternating InGaP and air.

15. The method of claim 9 , wherein the grating replaces an antireflective coating on the half VCSEL.

16. The method of claim 9 , wherein the forming the subwavelength grating comprises etching the half VCSEL device.

17. The method of claim 9 , wherein the subwavelength grating is defined by lithography.

18. 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.

Assignments (1)
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Apr 26, 2022
From: JOHNSON, BARTLEY C.
To: EXCELITAS TECHNOLOGIES CORP.
Reel/Frame 059732/0924 →
Continuity (2)
Provisional Application 63167209 · Mar 29, 2021
Related Publication 20220311213A1 · Sep 29, 2022
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