Wavelength locking filter

Patent metadata

Field	Value
Publication number	US-10782544-B2
Application number	US-201916597148-A
Country	US
Kind code	B2
Filing date	Oct 9, 2019
Priority date	Mar 25, 2015
Publication date	Sep 22, 2020
Grant date	Sep 22, 2020

Abstract

An optical system can automatically lock an adjustable spectral filter to a first wavelength of an incoming light signal, and can automatically filter an additional incoming light signal at the first wavelength. A tunable filter can have a filtering spectrum with an adjustable peak wavelength and increasing attenuation at wavelengths away from the adjustable peak wavelength. The tunable filter can receive first input light, having a first wavelength, and can spectrally filter the first input light to form first output light. A detector can detect at least a fraction of the first output light. Circuitry coupled to the detector and the tunable filter can tune the tunable filter to maximize a signal from the detector and thereby adjust the peak wavelength to match the first wavelength. The tunable filter further can receive second input light and spectrally filter the second input light at the first wavelength.

First claim

What is claimed is:

1. An optical system comprising:
a first input waveguide to deliver an incoming light beam having a variable wavelength that changes over time;
a tunable filter coupled to the first input waveguide to receive the incoming light beam, the tunable filter having an adjustable peak wavelength with increasing attenuation at wavelengths away from the adjustable peak wavelength, the tunable filter configured to continually adjust the adjustable peak wavelength to match the variable wavelength of the incoming light beam; and
a second input waveguide to deliver, to the tunable filter, an outgoing light beam having a wavelength, the tunable filter further configured to continuously adjust the wavelength of the outgoing light beam to match the adjustable peak wavelength as the variable wavelength of the incoming light beam changes over time.

2. The optical system of claim 1 , wherein the incoming light beam and the outgoing light beam simultaneously share one or more optical paths in the tunable filter.

3. The optical system of claim 2 , wherein the incoming light beam and the outgoing light beam co-propagate in a same direction on the one or more optical paths of the tunable filter.

4. The optical system of claim 2 , wherein the incoming light beam and the outgoing light beam counter-propagate in opposite directions on the one or more optical paths of the tunable filter.

5. The optical system of claim 1 , wherein the tunable filter comprises a first optical input and a corresponding first optical output, and further comprises a second optical input and a corresponding second optical output, the incoming light beam being received at the first optical input and output at the first optical output, and outgoing light beam being received at the second optical input and output at the second optical output.

6. The optical system of claim 5 , wherein the tunable filter further comprises:
a first detector configured to detect a portion of the incoming light beam output by the first optical output; and
first circuitry coupled to the first detector and the tunable filter, the first circuitry configured to tune the tunable filter to maximize a signal from the first detector and adjust the adjustable peak wavelength of the tunable filter to match the variable wavelength of the incoming light beam.

7. The optical system of claim 6 , wherein the optical system further comprises:
a tunable light source to generate the outgoing light beam;
a second detector configured to detect a portion of the outgoing light beam that is output by the second optical output of the tunable filter; and
second circuitry coupled to the second detector and the tunable light source, the second circuitry configured to tune the tunable light source to maximize a signal from the second detector and adjust the wavelength of the outgoing light beam to match the adjustable peak wavelength of the tunable filter and thereby match the variable wavelength of the incoming light beam as the variable wavelength changes over time.

8. The optical system of claim 7 , wherein the second circuitry is integral with the first circuitry.

9. The optical system of claim 7 , wherein the second circuitry is separate from the first circuitry.

10. The optical system of claim 7 , wherein the tunable filter comprises an optical ring resonator formed from at least one waveguide arranged in a closed path.

11. The optical system of claim 10 , wherein the tunable filter further comprises:
a material having a temperature-dependent refractive index disposed in an optical path of the optical ring resonator; and
a heater configured to controllably heat at least a portion of the material, and thereby change an optical path length around the optical ring resonator and thereby change a resonant wavelength of the optical ring resonator, wherein the first circuitry is further configured to tune the tunable filter by heating the portion of the material.

12. The optical system of claim 10 , wherein the tunable filter further comprises:
a material having a current-dependent refractive index via free-carrier absorption disposed in an optical path of the optical ring resonator; and
a forward-biased PIN diode configured to controllably inject current into at least a portion of the material, and thereby change an optical path length around the optical ring resonator and thereby change a resonant wavelength of the optical ring resonator, wherein the first circuitry is further configured to tune the tunable filter by injecting the current into the portion of the material.

13. The optical system of claim 10 , wherein the optical ring resonator has a free spectral range greater than a specified range of wavelengths for the incoming light beam.

14. The optical system of claim 10 , wherein the optical ring resonator is configured to propagate light in a first direction around the closed path and a second direction, opposite the first direction, around the closed path.

15. The optical system of claim 14 , further comprising:
a first input waveguide configured to inject the incoming light beam having the variable wavelength, into the optical ring resonator in the first direction; and
a first output waveguide configured to extract the incoming light beam from the optical ring resonator in the first direction.

16. The optical system of claim 15 , further comprising:
a second input waveguide configured to inject the outgoing light beam into the optical ring resonator in the second direction; and
a second output waveguide configured to extract the outgoing light beam from the optical ring resonator in the second direction.

17. The optical system of claim 16 , wherein a top silicon layer of a silicon-on-insulator wafer is shaped to define the optical ring resonator, the first and second input waveguides, and the first and second output waveguides.

18. The optical system of claim 15 , further comprising:
a second input waveguide configured to inject the outgoing light beam into the optical ring resonator in the first direction; and
a second output waveguide configured to extract the outgoing light beam from the optical ring resonator in the first direction.

19. The optical system of claim 18 , wherein a top silicon layer of a silicon-on-insulator wafer is shaped to define the optical ring resonator, the first and second input waveguides, and the first and second output waveguides.

20. A method for wavelength matching light using an optical system, the method comprising:
receiving, by a first input waveguide of the optical system, an incoming light beam having a variable wavelength that changes over time;
receiving, by a tunable filter of the optical system, the incoming light beam from the first input waveguide;
continually adjusting, using the tunable filter, an adjustable peak wavelength of the tunable filter to match the variable wavelength of the incoming light beam;
receiving, by the tunable filter, an outgoing light beam having a wavelength; and
continuously adjusting, using the tunable filter the wavelength of the outgoing light beam to match the adjustable peak wavelength as the variable wavelength of the incoming light beam changes over time.

Assignees

• Aurrion Inc

Inventors

• Guzzon Robert Silvio

Classifications

• G02F1/0156

  using free carrier absorption · CPC title

• G02F1/0147

  based on thermo-optic effects (G02F1/132 takes precedence) · CPC title

• G02B6/29341

  Loop resonators operating in a whispering gallery mode evanescently coupled to a light guide, e.g. sphere or disk or cylinder (evanescent coupling for sensing fluorescence G01N21/648) · CPC title

• G02F1/025 Primary

  in an optical waveguide structure (G02F1/017, {G02F1/2257} take precedence) · CPC title

• G02B6/29338

  Loop resonators · CPC title