Tunable all-pass optical filters with large free spectral ranges

• US 6,389,203 B1
• Filed: 05/17/2000
• Issued: 05/14/2002
• Est. Priority Date: 05/17/2000
• Status: Expired due to Term

• Current Assignee: RPX Corporation
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Jordan, Rebecca, Madsen, Christi Kay
• Primary Examiner(s): Mack, Ricky
• Assistant Examiner(s): Harrington, Alicia M.
• Application Number:
  US09/573,086
• Time in Patent Office: 727 Days
• Field of Search: 385/3, 385/24, 385/32, 385/50, 385/14, 385/42, 385/131, 385/132
• US Class Current: 385/50
• CPC Class Codes: G02B 6/12002 Three-dimensional structures
• CPC Class Codes: G02F 1/0147 based on thermo-optic effects G02F1/132 takes precedence
• CPC Class Codes: G02F 1/065 in an optical waveguide structure
• CPC Class Codes: G02F 1/3136 of interferometric switch type
• CPC Class Codes: G02F 2203/15 involving resonance effects, e.g. resonantly enhanced interaction

Abstract

In accordance with the invention, a tunable optical all-pass filter with a substrate-supported multilayer waveguiding structure. A first layer including a waveguiding optical ring resonator, a second layer for spacing, and a third layer including a curved waveguide. The curved waveguide is optically coupled to the resonator by two spaced apart optical couplers extending through the spacing layer, and tunability is provided by a first phase-shifter to control the optical pathlength of the resonator and a second phase-shifter operative on the waveguide to control the strength of coupling between the waveguide and the resonator. In one embodiment, the waveguide and the resonator are horizontally spaced apart in the non-coupling regions to provide optical isolation. In another, the waveguide and resonator can overlap horizontally, but the spacer layer is thicker in the non-coupling regions to provide optical isolation.

Claims

1. A tunable optical all-pass filter comprising:

a substrate;

a first layer on said substrate including a waveguide optical ring resonator;

a second layer;

a third layer including a curved waveguide;

the curved waveguide optically coupled to the optical ring resonator through the second layer by at least two optical couplers;

a first phase shifter for adjusting the optical pathlengths of the ring resonator; and

a second phase shifter for adjusting the path length of the waveguide between the two optical couplers.

2. The all-pass filter of claim 1 wherein the second layer is of uniform thickness and the curved waveguide is offset from the resonator in the regions outside the couplers to provide optical isolation between the waveguide and the resonator.

3. The all-pass filter of claim 1 wherein the second layer in the regions outside the coupler is sufficiently thick to provide optical isolation between the waveguide and the resonator.

4. The tunable filter of claim 1 wherein the first phase shifter comprises a heater thermally coupled to the ring resonator.

5. The tunable filter of claim 1 wherein the second phase shifter comprises a heater thermally coupled to the curved waveguide.

6. The tunable filter of claim 4 wherein the third layer has a refractive index with a larger temperature dependence than the first layer.

7. The tunable filter of claim 5 wherein the third layer has a refractive index with a larger temperature dependence than the first layer.

8. The tunable filter of claim 1 wherein the substrate comprises silicon, the first layer comprises silica, the second layer comprises silica and the third layer comprises a halogenated acrylate.