Optical attenuator

• US 6,351,329 B1
• Filed: 10/08/1999
• Issued: 02/26/2002
• Est. Priority Date: 10/08/1999
• Status: Expired due to Term

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Agere Systems Guardian Corp. (Broadcom, Inc.), Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Greywall, Dennis Stanley
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): TRA, TUYEN Q
• Application Number:
  US09/415,281
• Time in Patent Office: 872 Days
• Field of Search: 359/245, 359/267, 359/290, 359/291, 359/223, 359/224, 359/263, 359/276, 359/292, 359/293, 359/294, 359/295
• US Class Current: 359/290
• 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 26/0825 the reflecting element being a flexible sheet or membrane, e.g. for varying the focus flexible mirrors for cosmetic use A45D42/24
• CPC Class Codes: G02B 6/266 the optical element being an attenuator
• CPC Class Codes: G02B 6/3516 the reflective optical element moving along the beam path, e.g. controllable diffractive effects using multiple micromirrors within the beam
• CPC Class Codes: G02B 6/3518 the reflective optical element being an intrinsic part of a MEMS device, i.e. fabricated together with the MEMS device MEMS devices in general B81B; manufacture of MEM devices in general B81C; micromechanical devices controlling the direction of light G02B26/0833
• CPC Class Codes: G02B 6/352 the reflective optical element having a shaped reflective surface, e.g. a reflective element comprising several reflective surfaces or facets that function together
• CPC Class Codes: G02B 6/357 Electrostatic force electrostatic forces controlling reflecting elements in general G02B26/0841
• CPC Class Codes: G02B 6/3594 Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams

Abstract

An optical attenuator having a structure in which a membrane covers a cavity formed on a substrate is disclosed. The membrane covering the cavity formed in the substrate is movable relative to the bottom surface of the cavity constituting a deformable mirror. Movement of the membrane relative to the bottom surface of the cavity attenuates optical signals impinging on the surface thereof. The movement of the membrane relative to the bottom surface of the cavity attenuates impinging optical signals by controlling the angle at which such impinging optical signals are reflected from the membrane surface.

Claims

1. An optical attenuator, comprising:

a substrate, wherein the substrate has a cavity therein; and

a membrane, wherein the membrane covers the cavity in the substrate, wherein the membrane is adapted to receive optical signals, and wherein the membrane is configured to have a region for receiving optical signals that is removed from the center of the cavity.

2. The optical attenuator of claim 1 wherein the membrane attenuates the at least portion of the received optical signals in response to an electrostatic field generated between the membrane and a bottom surface of the cavity in the substrate.

3. The optical attenuator of claim 2 wherein the electrostatic field is generated by applying a bias voltage between the membrane and the bottom surface of the cavity.

4. The optical attenuator of claim 3 wherein the bias voltage applied between the membrane and the bottom surface of the cavity is less than about 50 volts.

5. The optical attenuator of claim 1 wherein the cavity in the substrate has a height less than about 5 μ

m.

6. The optical attenuator of claim 1 wherein the membrane has pores therethrough.

7. The optical attenuator of claim 6 wherein the pores have a diameter less than about 10 μ

m.

8. An optical communication system, comprising:

an optical attenuator, wherein the optical attenuator includes a substrate and a membrane, wherein the substrate has a cavity therein, wherein the membrane covers the cavity in the substrate, wherein the membrane is adapted to receive optical signals, and wherein the membrane is configured to have a region for receiving optical signals that is removed from the center of the membrane.

9. A method of attenuating optical signals, comprising the steps of:

providing an optical attenuator, wherein the optical attenuator includes a substrate and a membrane, wherein the substrate has a cavity therein, wherein the membrane covers the cavity in the substrate, and wherein the membrane is adapted to receive optical signals;

generating an electrostatic field between the membrane and a bottom surface of the cavity in response to a control signal, wherein the electrostatic field causes the membrane to move from a first orientation to a second orientation; and

directing the optical signal to a region of the membrane that is removed from the center of the membrane when the membrane is in the second orientation.

10. The method of claim 9 wherein the control signal is a bias voltage.

11. The method of claim 10 wherein the bias voltage is less than about 50 volts.

12. The method of claim 9 wherein the cavity in the substrate has a height less than about 5 μ

m.

13. The method of claim 9 wherein the membrane has pores therethrough.

14. The method of claim 13 wherein the pores have a diameter less than about 10 μ

m.

15. An optical attenuator, comprising:

a substrate, wherein the substrate has a cavity therein; and

a membrane, wherein the membrane covers the cavity in the substrate, wherein the membrane is adapted to receive optical signals, and wherein the membrane is configured to have a region for receiving optical signals that is removed from the center of the cavity wherein the membrane comprises one or more material layers and wherein the one or more material layers are selected from the group consisting of silicon nitride, silicon dioxide, polysilicon, and a metal.

16. A method of attenuating optical signals, comprising the steps of:

providing an optical attenuator, wherein the optical attenuator includes a substrate and a membrane, wherein the substrate has a cavity therein, wherein the membrane covers the cavity in the substrate, and wherein the membrane is adapted to receive optical signals;

generating an electrostatic field between the membrane and a bottom surface of the cavity in response to a control signal, wherein the electrostatic field causes the membrane to move from a first orientation to a second orientation; and

directing the optical signal to a region of the membrane that is removed from the center of the membrane when the membrane is in the second orientation wherein the membrane comprises one or more material layers and wherein the one or more material layers are selected from the group consisting of silicon nitride, silicon dioxide, polysilicon, and a metal.