MEMS based variable optical attenuator (MBVOA)

• US 20020080465A1
• Filed: 11/02/2001
• Published: 06/27/2002
• Est. Priority Date: 11/03/2000
• Status: Active Grant

• Current Assignee: Intpax Incorporated
• Original Assignee: Intpax Incorporated
• Inventors: Huang, Liji, Han, Naiqian
• Granted Patent: US 6,556,338 B2
• Time in Patent Office: Days
• US Class Current: 359/291
• CPC Class Codes: G02B 26/02 for controlling the intensity of light G02B26/004 takes precedence
• CPC Class Codes: G02B 6/266 the optical element being an attenuator

Abstract

The present invention discloses an optimized optical attenuator device. It includes the design of resonator formed by two identical mirrors, which are made by MEMS process. The structure realizes the minimum insertion loss. The two membranes are chosen to be with high reflection rate. Multiple layer or metal layer or mixture of them can produce membrane of high reflection rate. High reflection rate causes low tuning voltage for one certain attenuation range. To reduce the manufacture error and the cost, the two identical membranes can be formed by bonding two MEMS cells fabricated in the same process face to face. To further reduce the insertion loss, the input mode should match the residual basic mode in the resonator. The basic residual mode is the only one surviving in the resonator. A design of the resonator will guarantee this happen. Ripple is a key specification for present optical component. To achieve very low ripple device, all the interfaces of the MEMS device should be coated with anti-reflection coating. The lower the reflection rate is, the lower the ripple is. Charging will cause the control voltage craze while using the attenuator device. To eliminate the charging effect, the electrode should be attached to the conductive face to face layers during the tuning process, which means between the two electrodes, positive and negative, there should be no dielectric material to trap the charges. However, one or two very thin dielectric layers between the two conductive layer electrodes can improve the electric breakdown voltage. The dielectric material and the thickness are selected without generating severe charging effect, while the safety of MEMS device can be guaranteed. Finally, the device is controlled by a smart control system with the temperature and wavelength compensation functionality. The control system makes the device stable and will keep the attenuation fixed regardless the temperature or wavelength changing. A device should have communication interface with system.

Claims

1. A micro-electro-mechanical system (MEMS) device supports on a substrate comprising:

an electrically tunable membrane having an optically transparent portion for transmitting an optical signal through an optical path therethrough wherein said membrane having a reflection rate of at least 50% ; and

a plurality of optical path interfaces for said optical signal to transmit from a first material medium to a second material medium of different refraction indexes and an antireflection (AR) layer is disposed on each of said interfaces between said first material medium and second material medium.; and

transmission spectrum is employed to fabricate the MEMS device.

2. The MEMS device of claim 1 wherein:

said electrically tunable membrane comprising at least two membrane layers wherein each of said membrane layer having alternately a relative high and then a relative low refraction index between adjacent membrane layers. If chosen one layer, the layer should be with high refraction index.

3. The MEMS device of claim 1 wherein:

said electrically tunable membrane comprising three membrane layers wherein each of said three membrane layer having alternately a relative high and then a relative low refraction indexes between adjacent membrane layers. The top and bottom layers should be with high refraction index.

4. The MEMS device of claim 1 wherein:

said electrically tunable membrane comprising five membrane layers wherein each of said five membrane layers having alternately a relative high and then a relative low refraction indexes between adjacent membrane layers. The top and bottom layers should be with high refraction index.

5. The MEMS device of claim 1 further comprising:

a resonator comprising said electric tunable membrane as a first electric tunable membrane and a second electric tunable membrane opposite said first electric tunable membrane wherein said first and second electric tunable membranes having a substantially same reflection rate.

6. The MEMS device of claim 1 further comprising:

a resonator comprising said electric tunable membrane as a first electric tunable membrane and a second electric tunable membrane opposite said first electric tunable membrane by bonding a second MEMS device manufactured together with said MEMS device whereby said first and second electric tunable membranes having a substantially same reflection rate.

7. The MEMS device of claim 1 further comprising:

conductive layers for functioning as electrodes for electrically tuning said membrane wherein said conductive layers disposed directly facing each other without an intermediate dielectric layer and constituting face-to-face conductive layers.

8. The MEMS device of claim 1 further comprising:

conductive layers for functioning as electrodes for electrically tuning said membrane wherein said conductive layers disposed directly facing each other with an intermediate dielectric layer with a thickness less than a charge-buildup thickness is disposed between said conductive layers constituting breakdown preventive face-to-face conductive layers.

9. The MEMS device of claim 7 wherein:

at least two of said conductive layers are ring-shaped conductive layers if they are un-transparent conductive material.

10. The MEMS device of claim 1 further comprising:

a resonator having a particular transverse width, cavity length, and membrane curvature for providing a basic resonator residual mode to match a specified incident beam.

11. The MEMS device of claim 1 further comprising:

a resonator having a resonator residual basic mode represented by a residual parameter ω

₀ wherein said residual parameter is particularly designed to match the input mode with optical waist a beam diameter ω

of an incident beam whereby ω

=ω

₀.

12. The MEMS device of claim 1 further comprising:

an optical attenuator device comprising a voltage control means for electrically tuning said membrane.

13. The MEMS device of claim 1 further comprising:

an environmental compensation control means for electronically control said attenuator for compensating environmental performance variations.

14. The MEMS device of claim 13 wherein:

said environmental compensation control means further comprising a temperature compensation control means for electronically control said attenuator for compensating temperature performance variations.

15. The MEMS device of claim 13 wherein:

said environmental compensation control means further comprising a wavelength-shift compensation control means for electronically control said attenuator for compensating wavelength-shift performance variations.

18. The MEMS device of claim 17 wherein:

said multi-layer membranes comprising a plurality of layers with a sequence of alternating high-low refraction indexes whereby said membranes are provided with high reflection rates for increasing a tunable attenuation range and reducing a tuning voltage.

19. The MEMS device of claim 17 wherein:

said first and second multi-layer membranes are manufactured contemporaneously by employing an identical set of processing steps on a same semiconductor wafer.

20. The MEMS device of claim 17 wherein:

said first and second multi-layer membranes having a substantially identical reflection rate.

17. A micro-electro-mechanical system (MEMS) device supports on a substrate comprising:

a first and a second multi-layer membranes formed as two high reflection-rate membranes functioning as two mirrors of a resonator.; and

transmission spectrum is employed to fabricate the MEMS device.

21. A micro-electro-mechanical system (MEMS) device supports on a substrate comprising:

a first membrane and a second multi-layers on substrate formed as two high reflection-rate mirrors functioning as a resonator.; and

transmission spectrum is employed to fabricate the MEMS device.

22. The MEMS device of claim 21 wherein:

said first multi-layer membrane comprising a plurality of layers with a sequence of alternating high-low refraction indexes whereby said membranes are provided with high reflection rates for increasing a tunable attenuation range and reducing a tuning voltage.

23. The MEMS device of claim 21 wherein:

said second multi-layers on substrate are designed to be with the same reflection rate as the first membrane.

24. The MEMS device of claim 21 wherein:

said first membrane and said second multi-layer substrate having a substantially identical reflection rate.