Pradip M Mitra

US Patent:

6452187, Sep 17, 2002

Filed:

Aug 24, 2000

Appl. No.:

09/645377

Inventors:

Lewis Taylor Claiborne - Richardson TX
Pradip Mitra - Grand Prairie TX

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

H01L 3109

US Classification:

25037012, 25037013

Abstract:

A two-color photodetector for detecting two different bands of infrared radiation is described. The photodetector includes either a diffractive resonant optical cavity that resonates at the two colors of interest, or a diffractive resonant optical cavity that resonates at the first color and a vertical resonant optical cavity that resonates at the second color. By placing materials that absorb only one of the two colors at the appropriate locations within the resonate structure, the resultant signals include little cross-talk due to the opposite color. The two-color photodetector finds use in applications covering a wide portion of the infrared spectrum.

US Patent:

6828642, Dec 7, 2004

Filed:

Apr 17, 2001

Appl. No.:

09/836036

Inventors:

Lewis T. Claiborne - Richardson TX
Pradip Mitra - Grand Prairie TX

Assignee:

Lockhead Martin Corporation - Bethesda MD

International Classification:

H01L 310352

US Classification:

257440, 257 21, 2503381, 2503384

Abstract:

A diffraction grating coupled infrared photodetector for providing high performance detection of infrared radiation is described. The photodetector includes a three-dimensional diffractive resonant optical cavity formed by a diffraction grating that resonates over a range of infrared radiation wavelengths. By placing a limited number of p/n junctions throughout the photodetector, the photodetector thermal noise is reduced due to the reduction in junction area. By retaining signal response and reducing the noise, the sensitivity increases at a given operating temperature when compared to traditional photovoltaic and photoconductive infrared photodetectors up to the background limit. The photodetector device design can be used with a number of semiconductor material systems, can form one- and two-dimensional focal plane arrays, and can readily be tuned for operation in the long wavelength infrared and the very long wavelength infrared where sensitivity and noise improvements are most significant.

US Patent:

6882409, Apr 19, 2005

Filed:

Jun 25, 2003

Appl. No.:

10/603707

Inventors:

Bruno J. Evans - Keller TX, US
Pradip Mitra - Colleyville TX, US

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

G01C003/08
G01B011/26
G01J005/02

US Classification:

356 401, 356 501, 3561415, 25033901, 25033902, 25033905

Abstract:

A multi-spectral detector for use in a passive/active system and a method for use in identifying an object in a field of view are disclosed. The multi-spectral detection system comprises an optically dispersive element, a detector array, and an integrated circuit. The optically dispersive element is capable of separating received LADAR radiation and radiation received from a scene into a plurality of spectral components and distributing the separated spectral components; and a detector array. The detector array includes a plurality of detectors capable of detecting the LADAR radiation; and a plurality of detectors capable of detecting the spectral components of the scene radiation. The integrated circuit is capable of generating a plurality of electrical signals representative of predetermined characteristics of the detected LADAR radiation and the detected spectral components. The method comprises passively detecting scene radiation employing a detector array; and actively detecting LADAR radiation through the detector array in parallel with passively detecting the scene radiation.

US Patent:

6897447, May 24, 2005

Filed:

Dec 5, 2002

Appl. No.:

10/310613

Inventors:

Pradip Mitra - Colleyville TX, US

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

G01J005/02
H01L025/00

US Classification:

25033902, 2503384

Abstract:

A multi-spectral photodetector for detecting two or more different bands of infrared radiation is described. The photodetector includes a diffractive resonant optical cavity that resonates at the two or more infrared radiation bands of interest. By detecting infrared radiation at two or more discrete applied biases and by generating a spectral response curve for the photodetector at each of these biases, the response to each of the individual bands of infrared radiation can be calculated. The response to each band of infrared radiation can be found by deconvolving the response at each bias. The photodetector finds many uses including military and medical imaging applications and can cover a broad portion of the infrared spectrum.

US Patent:

6920290, Jul 19, 2005

Filed:

Jul 11, 2001

Appl. No.:

09/903330

Inventors:

Pradip Mitra - Grand Prairie TX, US

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

H04J014/02
H04B010/06

US Classification:

398207, 398 79, 398 82, 398 87, 398202, 398212

Abstract:

An array of diffraction grating coupled infrared photodetectors is coupled to corresponding high-speed amplifiers for creating a multiple channel high speed receiver for an optical communication system. Each photodetector includes a three-dimensional diffractive resonant optical cavity formed by a diffraction grating that resonates over a narrow range of wavelengths. By creating different resonant optical cavities, the receiver detects each optical channel individually, thereby simplifying receiver design. The receiver finds ready application in systems based upon high power COlasers and semiconductor lasers such as quantum cascade lasers allowing extremely long line of sight communication, such as between satellites. Other applications include ship to ship or ground to missile communications. These applications will benefit from increased jamming resistance and security.

US Patent:

7041983, May 9, 2006

Filed:

Oct 12, 2001

Appl. No.:

09/976559

Inventors:

Pradip Mitra - Grand Prairie TX, US

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

G01T 1/24

US Classification:

25037013, 438 73

Abstract:

The described embodiments of the present invention include a method for forming a radiation detector. A radiation absorption layer is formed on a substrate. A wider bandgap layer is formed on the radiation absorption layer. A passivation layer is formed on the wider bandgap layer. A doping layer is formed on the passivation layer. The doping layer is then patterned and dopant is driven from the patterned doping layer into the junction layer and the radiation absorption layer to form a doped region. The passivation layer is patterned to expose the doped region and an electrical contact to the doped region is formed.

US Patent:

7135698, Nov 14, 2006

Filed:

Dec 5, 2002

Appl. No.:

10/310246

Inventors:

Pradip Mitra - Colleyville TX, US

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

H01L 29/06
H01L 29/04
H01L 29/22
H01L 29/732

US Classification:

257 21, 257 53, 257 98, 257 90, 257184, 25033902, 2503384, 2503391, 2503381

Abstract:

A multi-spectral super-pixel photodetector for detecting four or more different bands of infrared radiation is described. The super-pixel photodetector includes two or more sub-pixel photodetectors, each of which includes a diffractive resonant optical cavity that resonates at two or more infrared radiation bands of interest. By detecting infrared radiation at two or more different applied biases and by generating a spectral response curve for each of the sub-pixel photodetectors at each of these biases, the response to each of the individual bands of infrared radiation can be calculated. The response to each band of infrared radiation can be found by deconvolving the response at each bias. The super-pixel photodetector finds use in military and medical imaging applications and can cover a broad portion of the infrared spectrum.

US Patent:

7214195, May 8, 2007

Filed:

Jul 23, 2003

Appl. No.:

10/625155

Inventors:

Pradip Mitra - Colleyville TX, US

Assignee:

Lockheed Martin Corporation - Bethesda MD

International Classification:

A61B 5/00

US Classification:

600549, 600473, 600474

Abstract:

A method of and apparatus for detecting diseased tissue based upon infrared imaging in two different bands of infrared wavelengths is described. The use of two series of infrared images taken in two different bands of infrared wavelengths increases sensitivity to the subtle temperature changes caused by diseased skin and tissue, especially in the case of cancerous tissue. By sensing skin temperature, the homogeneity thereof, the time variations thereof and the correlation between the two series of infrared images, the present invention decreases the rate of false positives and false negatives. The increased discrimination due to two series of infrared images allows for reliable detection of diseased or cancerous tissue even in the presence of skin tone variations such as birthmarks, tattoos and freckles. The present invention finds special application in the field of breast cancer detection where subtle skin temperature variations may readily be sensed using two series of infrared images.