# US 8,569,696 B2 · Imaging system and method using a photonic band gap array

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- Number: US 8,569,696 B2
- Document ID: US8569696B2
- Status: Granted
- Kind: B2
- Application number: 11/668,600
- Filed: 2007-01-30
- Published: 2008-07-31
- Granted: 2013-10-29
- Earliest claimed: 2007-01-30
- Assignees: Raytheon Company
- Applicants: Delmar L. Barker; Abram G. Young; William R. Owens
- Inventors: Delmar L. Barker; Abram G. Young; William R. Owens
- Web page: https://patentgrep.com/patent/US8569696B2

## CPC

- G02B 6/1225: {comprising photonic band-gap structures or photonic lattices}
- B82Y 20/00: Nanooptics, e.g. quantum optics or photonic crystals
- G01J 5/06: Arrangements for eliminating effects of disturbing radiation; Arrangements for compensating changes in sensitivity (for adjusting of solid angle of collected radiation G01J5/07; means for wavelength selection G01J5/0801)
- G01J 5/0818: Waveguides
- G01J 5/0853: {having infrared absorbers other than the usual absorber layers deposited on infrared detectors like bolometers, wherein the heat propagation between the absorber and the detecting element occurs within a solid}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)

## Abstract

An imaging system (20) includes an array (24) of photonic band gap material cells. The band gap material has an absorption edge at about the emission frequency of a source (22) of electromagnetic energy. Images from a field of view (26) directed onto the photonic band gap array (24) increase the temperature of the illuminated cells, shifting the absorption edge frequency for those cells. A focal plane array (28) detects the electromagnetic radiation transmitted through the photonic band gap array (24) from the source (22). The intensity of the transmitted radiation is proportional to the shift in the photonic band gap edge.

## Claims

### Claim 1

A system comprising:
a source of narrow bandwidth electromagnetic radiation having a specified wavelength;
an array of photonic band gap material cells positioned to receive the electromagnetic radiation from the source, each cell having a photonic band gap material with an absorption edge at about the emission frequency of the source of electromagnetic radiation;
an optical assembly arranged to direct electromagnetic radiation from a field of view onto the photonic band gap array and thereby shift the absorption edge of the cells illuminated by the electromagnetic radiation from the field of view; and
a focal plane array positioned to receive electromagnetic radiation from the photonic band gap array and to detect electromagnetic radiation with the specified wavelength,
wherein the photonic band gap material has a lattice structure that expands approximately 0.25% per 10 C temperature rise, resulting in an approximately 4 to 10 decibel change in the transmission of the electromagnetic radiation.

### Claim 2 (depends on 1)

A system as set forth in claim 1, wherein the source is selected from a laser and a light emitting diode.

### Claim 3 (depends on 1)

A system as set forth in claim 1, wherein the source emits electromagnetic radiation having an approximately near infrared wavelength.

### Claim 4 (depends on 1)

A system as set forth in claim 1, wherein the source is a 0.85 micrometer wavelength laser.

### Claim 5 (depends on 1)

A system as set forth in claim 1, wherein the photonic band gap array is thermally isolated from the focal plane array.

### Claim 6 (depends on 1)

A system as set forth in claim 1, wherein the photonic band gap array is thermally isolated from the focal plane array by an aerogel.

### Claim 7 (depends on 1)

A system as set forth in claim 1, wherein the photonic band gap array includes a first material having a relatively low degree of thermal expansion and a second material having a relatively high degree of thermal expansion.

### Claim 8 (depends on 1)

A system as set forth in claim 1, wherein the photonic band gap material has a high degree of absorption in a wavelength of interest to maximize absorption edge shift.

### Claim 9 (depends on 1)

A system as set forth in claim 1, wherein the photonic band gap material has a high degree of absorption in an infrared wavelength of interest to maximize absorption edge shift.

### Claim 10 (depends on 1)

A system as set forth in claim 1, wherein the photonic band gap material includes units of a first material dispersed within a second material at regular intervals of approximately “a”, each unit of the first material having a dimension of approximately 2r, and a lattice constant is defined as r/a and decreases proportionately with temperature.

### Claim 11 (depends on 1)

A system as set forth in claim 1, wherein the optical assembly includes a device which transmits electromagnetic radiation of a first wavelength and reflects electromagnetic radiation of a second wavelength.

### Claim 12 (depends on 1)

A system as set forth in claim 1, wherein the focal plane array includes an image sensor.

### Claim 13 (depends on 1)

A system as set forth in claim 1, wherein the focal plane array includes a charge coupled device (CCD).

### Claim 14 (depends on 1)

A system as set forth in claim 1, wherein the photonic band gap array and the focal plane array are contained in a housing lined with a photonic band gap material that inhibits electromagnetic radiation with wavelengths of about eight to twelve micrometers.