# US 6,724,125 B2 · Methods and apparatus for diffractive optical processing using an actuatable structure

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- Number: US 6,724,125 B2
- Document ID: US6724125B2
- Status: Granted
- Kind: B2
- Application number: 10/090,380
- Filed: 2002-03-04
- Published: 2002-11-14
- Granted: 2004-04-20
- Earliest claimed: 1999-03-30
- Assignees: Massachusetts Institute of Technology
- Inventors: Elmer S. Hung; Erik R. Deutsch; Stephen D. Senturia
- Web page: https://patentgrep.com/patent/US6724125B2

## CPC

- G02B 6/3516: {the reflective optical element moving along the beam path, e.g. controllable diffractive effects using multiple micromirrors within the beam}
- G02B 6/2931: {Diffractive element operating in reflection}
- G02B 6/29383: {Adding and dropping}
- G02B 6/357: {Electrostatic force (electrostatic forces controlling reflecting elements in general G02B26/0841)}
- G02B 6/3588: {of the processed beams, i.e. controlling during switching of orientation, alignment, or beam propagation properties such as intensity, size or shape}
- G02B 6/4246: {Bidirectionally operating package structures}
- G02B 26/0808: {by means of one or more diffracting elements}
- H02N 1/006: {of the gap-closing type (H02N1/004 takes precedence)}
- H04J 14/0201: {Add-and-drop multiplexing}
- G02B 6/3524: {the optical element being refractive}
- G02B 6/356: {in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links (switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001)}
- G02B 6/3584: {constructional details of an associated actuator having a MEMS construction, i.e. constructed using semiconductor technology such as etching (MEMS per se B81B, B81C)}
- G02B 6/3594: {Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams}
- G02B 6/3598: {Switching means directly located between an optoelectronic element and waveguides, including direct displacement of either the element or the waveguide, e.g. optical pulse generation (based on changing the optical properties of the medium G02F1/00; optical pulse generation in optical transmitters H04B10/508; optical pulse generation by controlling laser operation H01S3/00)}
- H04J 14/0204: {Broadcast and select arrangements, e.g. with an optical splitter at the input before adding or dropping}
- H04J 14/0205: {Select and combine arrangements, e.g. with an optical combiner at the output after adding or dropping}
- H04J 14/0213: {Groups of channels or wave bands arrangements}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H02N: ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

A method of redirecting light using an actuatable two-layer diffraction grating structure, the method having applications in wavelength-division multiplexed systems. An optical add/drop modulator (OADM) including an actuatable diffraction grating, for use with a wavelength-division multiplexed signal. An OADM having an optical source located off the main pathway to direct a optical carrier to be added onto the actuatable diffraction grating such that the carrier is diffracted into the main pathway. A detector to measure signal strength for use with an optical processor, the optical processor having an actuatable structure having gaps between the actuated portion of the structure. The detector detecting the portions of light diffracted by the gaps.

## Claims

### Claim 1

A method of redirecting light from a main pathway using a diffracting optical element having a plurality of reflective grating elements, comprising:
supporting a plurality of actuating beams over a substrate, each of the plurality of actuating beams forming a corresponding actuation gap relative to the substrate, the plurality of actuating beams forming a plurality of rows, each row including a corresponding at least two of the plurality of actuating beams;
supporting each of the plurality of grating elements over a corresponding one of the plurality of rows of actuating beams to form a corresponding auxiliary gap therebetween;
directing a beam of light along the main pathway and onto a portion of each of the plurality of grating elements, the beam having at least light of a first wavelength and light of a second wavelength; and
positioning at least one of the plurality of grating elements relative to the substrate by actuating the at least two of the actuating beams corresponding to at least one of the plurality of rows of actuating beams, the positioning causing at least a portion of one of the light of a first wavelength and the light of a second wavelength to be diffracted out of the main pathway, whereby the planarity of the at least one of the plurality of grating elements is maintained over the portion of the at least one of the plurality of grating elements onto which the beam of light is directed.

### Claim 2 (depends on 1)

The method of claim 1 wherein the light of a first wavelength and the light of a second wavelength are from a broadband source.

### Claim 3 (depends on 1)

The method of claim 1 further comprising spatially separating the light of a first wavelength and the light of a second wavelength prior to directing the beam of light onto the plurality of grating elements.

### Claim 4 (depends on 3)

The method of claim 3 wherein the light of a first wavelength is an optical carrier in a DWDM signal.

### Claim 5 (depends on 4)

The method of claim 4 wherein the optical carrier is dropped.

### Claim 6 (depends on 4)

The method of claim 4 wherein the optical carrier is asymmetrically diffracted.

### Claim 7 (depends on 4)

The method of claim 4 wherein the method is used to block optical carriers in an OADM multiplexer system.

### Claim 8

A method of processing a first optical carrier of a wavelength-division multiplexed signal using a diffracting optical element having a plurality of reflective grating elements and a main pathway, comprising:
supporting a plurality of actuating beams over a substrate, each of the plurality of actuating beams forming a corresponding actuation gap relative to the substrate, the plurality of actuating beams forming a plurality of rows, each row including a corresponding at least two of the plurality of actuating beams;
supporting each of the plurality of grating elements over a corresponding one of the plurality of rows of actuating beams to form a corresponding auxiliary gap therebetween;
directing the first optical carrier along the main pathway and onto a portion of each of the plurality of grating elements; and
positioning at least one of the plurality of grating elements relative to the Substrate by actuating the at least two of the actuating beams corresponding to at least one of the plurality of rows of actuating beams, the positioning modifying the optical strength of the first optical carrier along the main pathway, whereby the planarity of the at least one of the plurality of grating elements is maintained over the portion of the at least one of the plurality of grating elements onto which the beam of light is directed.

### Claim 9 (depends on 8)

The method of claim 8 further comprising spatially separating the first optical carrier from a second optical carrier prior to the directing the first optical carrier onto the plurality of grating elements.

### Claim 10 (depends on 9)

The method of claim 9 wherein the positioning causes the first optical carrier to be dropped.

### Claim 11 (depends on 9)

The method of claim 9 wherein the first optical carrier is asymmetrically diffracted.

### Claim 12 (depends on 9)

The method of claim 9 wherein the method is used to block optical carriers in an OADM multiplexer system.

### Claim 13

An optical processing apparatus comprising:
(A) an optical source to produce a beam having light of a first wavelength and light of a second wavelength;
(B) a diffracting optical element having a main pathway, arranged to receive the beam of light along a main pathway, the diffracting optical element having,
(i) a plurality of conductive actuating beams each supported over a substrate by a corresponding at least two actuation beam support posts, each of the plurality of actuating beams forming an actuation gap relative to the substrate, the plurality of conductive actuating beams arranged to form a plurality of rows of actuating beams, each row of actuating beams including at least two of the plurality of actuating beams,
(ii) a plurality of grating elements arranged to receive the beam of light, each of the plurality of grating elements supported over a corresponding one of the plurality of rows of actuating beams by a corresponding at least two auxiliary beam support post, the corresponding at least two auxiliary beam support posts arranged to form an auxiliary gap between one of the plurality of grating elements and the corresponding one of a plurality of rows of actuating beams, the auxiliary beam posts located such that upon actuation of the actuating beams corresponding to a row of actuating beams in the direction of the substrate, the corresponding grating element is displaced in the direction of the substrate and planarity of the grating element is maintained, and
(iii) at least one electrode disposed on the substrate;
(B) a controller adapted to establish a voltage between the at least one electrode and the at least two actuating beams corresponding to one of the plurality of the plurality of rows of actuating beams, in a manner such that upon establishment of the voltage, at least a portion of one of the light of a first wavelength and the light of a second wavelength is diffracted out of the main pathway.

### Claim 14 (depends on 13)

The optical processing apparatus of claim 13 wherein the optical source is an optical fiber.

### Claim 15 (depends on 13)

The optical processing apparatus of claim 13 further comprising a demultiplexer optically coupled to the optical source to achieve spatial separation of the light of a first wavelength and the light of a second wavelength and to project the light of a first wavelength and the light of a second wavelength onto the diffracting optical element.

### Claim 16 (depends on 13)

The optical processing apparatus of claim 13 wherein the light of a first wavelength and the light of a second wavelength correspond to a first optical carrier and a second optical carrier in a WDM signal, respectively.

### Claim 17 (depends on 13)

The optical processing apparatus of claim 13 wherein the controller is adapted to drop one of the first optical carrier and second optical carrier.