Tilt mirror fabry-perot filter system, fabrication process therefor, and method of operation thereof

• US 20030011864A1
• Filed: 07/16/2001
• Published: 01/16/2003
• Est. Priority Date: 07/16/2001
• Status: Active Grant

• Current Assignee: Excelitas Technologies Corporation (Excelitas Technologies Holdings LLC)
• Original Assignee: Axsun Technologies Incorporated
• Inventors: Flanders, Dale C.
• Granted Patent: US 6,594,059 B2
• Time in Patent Office: Days
• US Class Current: 359/230
• CPC Class Codes: B81B 3/0035 Constitution or structural means for controlling the movement of the flexible or deformable elements
• CPC Class Codes: G01J 3/26 using multiple reflection, e.g. Fabry-Perot interferometer, variable interference filters
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G02B 6/29358 Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator G02B6/29347, G02B6/29349, G02B6/2935, G02B6/29361 take precedence; resonator evanescently coupled to light guide G02B6/29335
• CPC Class Codes: G02B 6/29395 configurable, e.g. tunable or reconfigurable switching G02B6/35

Abstract

A tilt mirror Fabry-Perot tunable filter comprises a frame and a first mirror structure. A tether system connects the first mirror structure to this frame. The tether system is designed to enable the tilting of the first mirror structure relative to an optical axis, in addition to translation of the first mirror structure along the optical axis. A second mirror structure is further provided to define an optical cavity in combination with the first mirror structure. At least two drive electrodes are provided for electrostatically tilting and translating the first mirror structure. The resulting MEMS Fabry-Perot tunable filter is capable for hitless tuning. It can be tuned to between bands directly, i.e., without dropping intervening bands.

Claims

1. A tilt mirror tunable filter, comprising:

a frame;

a first mirror structure;

a tether system connecting the first mirror structure to the frame, the tether system enabling tilting of the first mirror structure relative to an optical axis and translation of the first mirror structure along the optical axis;

a second mirror structure defining an optical cavity in combination with the first mirror structure; and

at least two drive electrodes for electrostatically tilting and translating the first mirror structure.

2. A tilt mirror tunable filter as claimed in claim 1, further comprising a support and a device layer on the support, wherein the frame and the tether system are fabricated in the device layer, the tether system being released from the support to suspend the first mirror structure above the support.

3. A tilt mirror tunable filter as claimed in claim 2, wherein the tether system is released from the support by removal of a sacrificial structure.

4. A tilt mirror tunable filter as claimed in claim 3, wherein the sacrificial structure comprises silicon and silicon oxide sacrificial layers.

5. A tilt mirror tunable filter as claimed in claim 2, wherein the support comprises an optical port that is formed though the support along an optical axis of the filter.

6. A tilt mirror tunable filter as claimed in claim 1, wherein the first and second mirror structures comprise thin film dielectric mirror coatings.

7. A tilt mirror tunable filter as claimed in claim 1, wherein the first mirror structure comprises a thin film dielectric mirror coating and a body portion, which connects the tether system to the mirror coating.

8. A tilt mirror tunable filter as claimed in claim 1, wherein at least one of the first mirror structure and the second mirror structure comprises a curved mirror.

9. A tilt mirror tunable filter as claimed in claim 8, wherein a sag of the curved mirror enables spoiling of the optical cavity in response to tilting of the first mirror structure.

10. A method for hitless tuning of a MEMS tilt mirror tunable filter, the method comprising:

controlling electrostatic fields between at least two fixed electrodes and first mirror structure to tilt the first mirror structure relative to a second mirror structure and spoil an optical cavity defined by the first mirror structure and the second mirror structure;

controlling the electrostatic fields between the fixed electrodes and the first mirror structure to translate the mirror structure relative to an optical axis of the optical cavity thereby changing a length of the optical cavity, and

controlling the electrostatic fields between the fixed electrodes and the first mirror structure to tilt the first mirror structure relative to the second mirror structure and realign the optical cavity.

11. A method as claimed in claim 10, wherein the first mirror structure is connected to the frame via a tether system.