Robert F. Cannata

InGaAs NIR focal plane arrays for imaging and DWDM applications

Indigo Systems Corporation has recently developed a line of high performance NIR devices and cameras based upon InGaAs detector arrays. The InGaAs detector arrays are fabricated at Indigo Systems Detector Operations facility and include 640x512 and 320x256 staring focal plane arrays which are utilized in three camera configurations ranging from the miniature alpha camera to the Merlin and Phoenix high performance cameras. The InGaAs detector arrays are very high performance devices with operability routinely exceeding 99.9%. In addition to the staring arrays for imaging applications, two varieties of linear arrays are also being produced at Indigo Systems Detector Operations including a 512 element and 1024 element devices. The linear arrays are intended for use in telecommunications for DWDM applications and are provided in industry standard packages for insertion into DWDM systems. All linear arrays require 100% perfect operability and this is routinely achieved.

Very wide dynamic range SWIR sensors for very low background applications

This paper describes a high performance 320 by 256 readout integrated circuit (ROIC) designed for P-on-N short wave IR (SWIR) detectors including InGaAs and HgCdTe, which also has the ability to operate at low input current levels with N- on-P detectors. The ROIC/FPA will support a wide range of system requirements from very low background applications to daytime high illumination conditions. To accommodate the wide scene dynamic range requirements, two selectable integration capacitors are used to control the input circuit transimpedance gain. A 10fF integration capacitor is used for low noise and low flux levels down to 10-5 ft Lambert, corresponding to approximately 2 X 1010 ph/cm2-sec for 0.9 micrometers to 1.7 micrometers spectral band using f/1.5 optics, assuming a 2856 Kelvin blackbody distribution. For higher flux levels, a 0.21pF integration capacitor can be selected, thus providing over a factor of 20 dynamic range. A capacitive feedback transimpendance amplifier provides a low noise detector interface circuit capable of operating at low input currents without frame-to- frame image lag. A sample and hold capacitor is also part of the input unit cell architecture, which allows the FPA to be operated in full frame snapshot mode and provides the maximum integration time available. The integration time is electronically controlled by an external clock pulse, and is adjustable form 0.5microsecond(s) ec to approximately the frame time of 33.3 msec for 30Hz operation. This produces an additional factor of 66,000 to the total nine orders of magnitude in scene dynamic range.

Microbolometer development and production at Indigo Systems

While microbolometers have been in production for several years, the number of companies producing them is quite small. Indigo Systems has entered into the development and production of VOx based microbolometers, at its Goleta facility. Through the investment of significant capital, Indigo has established a high volume production facility based on the silicon industry model. The 6-inch, cassette-to-cassette, highly automated facility is capable of yielding hundreds of thousands of die per year. Discussed in the paper will be the design and layout of the facility, performance of the devices, as well as yield, trend and throughput data.

Microbolometer production at Indigo Systems

Indigo’s emergence as a production source of uncooled microbolometers was reported in the SPIE proceeding in 2003. With now over a year of modest volume production history on the small-format FPAs, the details of the production experiences are reported. Progress on the mid-format arrays is discussed as are the efforts towards large-format, small pixel devices. Also discussed is the status of the production ramp that will lead to the supply of uncooled FPAs into the automotive market.

Standardized high performance readout integrated circuits enable rapid development of QWIP imaging systems

Abstract This paper describes standardized high performance 320 by 256 (ISC9705 or ‘Standard 320’) and 640 by 512 (ISC9803 or ‘Standard 640’) readout integrated circuits (ROICs) for detectors such as InSb, InGaAs, and QWIP, including presentation of focal plane array (FPA) test results for QWIP FPAs fabricated on the ISC9705 and ISC9803 ROICs. The availability of detector interface layout databases, complete test results for each die, and off-the-shelf imaging electronics enable rapid development of imaging systems using QWIP detector arrays. The ROICs are intended to support a wide range of systems through flexibility and advanced modes of operation, and include features such as high-detector bias, programmable gain and signal ‘skimming’ to improve the performance of QWIP FPAs fabricated with these devices. The ROICs also support such advanced features as dynamic image transposition, dynamic windowing, multiple high-speed output configurations, and flexible snapshot integration. These arrays are part of the Indigo Systems family of standard ROICs that share a common architecture and electrical interface.

Design and testing of a high-speed low-noise infrared detector array

For infrared laser remote sensing, a direct detection receiver may be optimally designed around a high speed, low noise focal plane array (FPA). Short pulse, high repetition rate operation of the laser transmitter makes it beneficial to operate the detector with short integration times, lowering the limiting integrated background photon flux. With this photon signal (which constitutes a noise contribution) made small enough, improved low-noise readout integrated circuits (ROIC) can be used to realize a significantly improved imaging lidar receiver. A 10 by 10 pixel ROIC has recently been designed and fabricated. Demonstrated capabilities include > 100 kHz frame rate, 50 ns integration time, and less than 100 e- of input-referred readout noise. These ROICs have been mated with long-wavelength HgCdTe infrared detector arrays, with cutoff wavelengths greater than 11 micrometer. Characteristics of the demonstrated ROIC design will be presented, along with testing of the focal plane arrays hybridized to them.