Quantum efficiency (QE) restricted infrared focal plane arrays

Abstract

A sensor includes an InGaAs photodetector configured to convert received infrared radiation into electrical signals. A notch filter is operatively connected to the InGaAs photodetector to block detection of wavelengths within at least one predetermined band. An imaging camera system includes an InGaAs photodetector configured to convert received infrared radiation into electrical signals, the InGaAs photodetector including an array of photodetector pixels each configured to convert infrared radiation into electrical signals for imaging. At least one optical element is optically coupled to the InGaAs photodetector to focus an image on the array. A notch filter is operatively connected to the InGaAs photodetector to block detection of wavelengths within at least one predetermined band. A ROIC is operatively connected to the array to condition electrical signals from the array for imaging.

Claims

1. A sensor comprising: an InGaAs photodetector configured to convert received infrared radiation into electrical signals; and a notch filter operatively connected to the InGaAs photodetector, wherein the notch filter is configured to block detection of wavelengths within each of three respective, non-overlapping bands, one band including 850 nm, one band including 1060 nm, and one band including 1550 nm.

2. The sensor as recited in claim 1, wherein the InGaAs photodetector is sensitive to at least one of SWIR or NIR radiation outside the at least one predetermined band.

3. The sensor as recited in claim 1, further comprising a ROIC operatively connected to the InGaAs photodetector to condition electrical signals from the InGaAs photodetector.

4. The sensor as recited in claim 1, wherein the InGaAs photodetector is configured to receive wavelengths up to and including 1700 nm.

5. The sensor as recited in claim 1, further comprising a filter assembly optically coupled to the InGaAs photodetector to improve signal to noise ratio.

6. The sensor as recited in claim 1, wherein the notch filter includes an optical coating directly on a surface of the InGaAs photodetector.

7. The sensor as recited in claim 5, wherein the optical coating is monolithic with the InGaAs photodetector.

8. The sensor as recited in claim 1, wherein the notch filter is securely embedded in an optical path of the InGaAs photodetector.

9. The sensor as recited in claim 1, wherein the InGaAs photodetector includes a two-dimensional array of photodetector pixels each configured to convert infrared radiation into electrical signals for imaging.

10. The sensor as recited in claim 9, further comprising a ROIC operatively connected to the two-dimensional array of photodetector pixels to condition electrical signals from the two-dimensional array for imaging.

11. An imaging camera system comprising: an InGaAs photodetector configured to convert received infrared radiation into electrical signals, the InGaAs photodetector including an array of photodetector pixels each configured to convert infrared radiation into electrical signals for imaging; at least one optical element optically coupled to the InGaAs photodetector to focus an image on the array; a notch filter operatively connected to the InGaAs photodetector, wherein the notch filter is configured to block detection of wavelengths within each of three respective, non-overlapping bands, one band including 850 nm, one band including 1060 nm, and one band including 1550 nm; and a ROIC operatively connected to the array to condition electrical signals from the array for imaging.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) So that those skilled in the art to which the subject disclosure appertains will readily understand how to make and use the devices and methods of the subject disclosure without undue experimentation, preferred embodiments thereof will be described in detail herein below with reference to certain figures, wherein:

(2) FIG. 1 is a schematic perspective view of an exemplary embodiment of an imaging camera system constructed in accordance with the present disclosure, showing an optical element for focusing an image on a sensor for imaging;

(3) FIG. 2 is an exploded, schematic perspective view of a portion of the system of FIG. 1, showing the imaging sensor, optical elements, and filters; and

(4) FIG. 3 is a graph showing quantum efficiency as a function of wavelength for two exemplary embodiments of sensors in accordance with the present disclosure, and showing exemplary predetermined bands for blocking detection of wavelengths by the sensor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an exemplary embodiment of an imaging camera system in accordance with the disclosure is shown in FIG. 1 and is designated generally by reference character 100. Other embodiments of sensors in accordance with the disclosure, or aspects thereof, are provided in FIGS. 2-3, as will be described. The systems and methods described herein can be used for infrared detection and imaging that excludes predetermined wavelengths.

(6) An imaging camera system 100 includes a sensor 102 that includes an InGaAs photodetector configured to convert received infrared radiation, indicated by the triple arrows in FIGS. 1-2, into electrical signals. The InGaAs photodetector includes a two-dimensional array of photodetector pixels, indicated by the grid texture on sensor 102 in FIG. 2. Each pixel is configured to convert infrared radiation into electrical signals for imaging. At least one optical lens element 106 is optically coupled to the InGaAs photodetector to focus an image on the array, so the sensor 102 functions as a focal plane array (FPA), however embodiments including only a single photodetector, a one-dimensional array of photodetector pixels, or any other suitable configuration are all contemplated within the scope of this disclosure. A notch filter 108 is operatively connected to the InGaAs photodetector of sensor 102 to block detection of wavelengths within at least one predetermined band. A Read-Out Integrated Circuit (ROIC) 104 is operatively connected to the array of sensor 102 to condition electrical signals from the array for imaging.

(7) The notch filter 108 includes an optical coating directly on a surface of the InGaAs photodetector of sensor 102, as indicated by the dashed lines in FIG. 8 associated with reference character 108. The optical coating can be monolithic with the InGaAs photodetector, and can be applied to the InGaAs detector by any suitable film deposition technique, e.g., for high volume commercial semiconductor processing. It is also contemplated in addition to or in lieu of notch filter 108, that the notch filter can be securely embedded in an optical path of the InGaAs photodetector, e.g., spaced apart from the InGaAs photodetector such as indicated in FIG. 2 with the broken line associated with reference character 110. A single notch filter can be used, or multiple notch filters, each for blocking a respective bandwidth or bandwidths, can be used at any suitable position in the optical path of system 100 leading to sensor 102. A filter assembly, e.g., included in the notch filter 108/110 or separate therefrom, can be optically coupled to the InGaAs photodetector to improve signal to noise ratio.

(8) With reference now to FIG. 3, the InGaAs photodetector of sensor 102 can be configured to receive wavelengths up to and including 1700 nm. In FIG. 3, quantum efficiency curves are shown for two exemplary InGaAs photodetectors, each having a cutoff at or around 1700 nm. The sensor 102 for Example 1 has a higher quantum efficiency for visible light than the sensor 102 for Example 2, however in both examples the InGaAs photodetector is sensitive to at least one of SWIR (e.g. wavelengths from 1.4-3.0 m) or NIR (e.g., wavelengths from 0.75-1.4 m) radiation outside the at least one predetermined bands of notch filter 108/110. The notch filter 108/110 can be configured to block detection of wavelengths within predetermined bands including 850 nm, 1060 nm, and/or 1550 nm. The notch filter 108/110 for each of these two examples is configured to reflect or block detection of wavelengths within each of three respective, non-overlapping bands, one band including 850 nm 20 nm, one band including 1060 nm20 nm, and one band including 1550 nm20 nm, as indicated in FIG. 3 by the rectangles. The 40 nm notch width in these examples can vary without departing from the scope of this disclosure, as can the centers of the notch bandwidth, as can the number of notches, as needed on an application by application basis. Eliminating detection of radiation in the notches of notch filter 108/110 allows for use in applications where it is desired to detect radiation across various portions of the spectrum of sensitivity for the InGaAs photodetector, wherein it is also desirable to prevent detection of radiation in the notch bands of notch filter 108/110, such as radiation from specific laser sources centered around the 860, 1060, and 1550 nm wavelengths. For example, there are applications which can benefit from ensuring that such laser sources do not interfere with the two-dimensional imagery obtained from an infrared sensor.

(9) The methods and systems of the present disclosure, as described above and shown in the drawings, provide for sensors with superior properties including the ability to image while excluding certain predetermined wavelengths. While the apparatus and methods of the subject disclosure have been shown and described with reference to preferred embodiments, those skilled in the art will readily appreciate that changes and/or modifications may be made thereto without departing from the scope of the subject disclosure.