Uncooled Photodetectors in YAG/CO2 Laser Warning Receivers
On the modern battle field there is an ever growing need for protection
against laser-aided weapons. The modern laser warning receiver detects,
identifies and characterizes optical signals 360o around the vehicle,
precisions direction and angle of arrival and provides warning and
identification of laser threats to the crew. The detection of the UV, V, short
and middle IR radiation is relatively straightforward, the detection of 10.6 mm
CO2 radiation is much more difficult. The paper contains a brief
characteristic of uncooled wide spectral band photodetectors presently
manufactured at VIGO, which can be used in laser warning receivers.
Currently manufactured Laser Warning Receivers utilize uncooled silicon detectors for detection of UV, visible and very short IR radiation (0.3-1.1 mm). The detection of short and middle wavelength radiation can be achieved by the use of uncooled PbS (<2.5 mm), InAs (<3.5 mm), PbSe (<4 mm) and InSb (<5 mm). There is increasing use of 10.6 mm CO2 lasers, and in consequence, growing demand for fast long-wave radiation detectors. Thermal detectors as thermopiles and pyroelectric detector have too low performance at high frequencies.
High sensitivity and fast detection of long-wavelength radiation can be achieved by the use of cryogenically cooled semiconductor photodetectors. However the need for cooling is extremely troublesome in battle field. Great progress has bean achieved with the introduction of the four-stage thermal-electric cooled (to 200 K) HgCdTe photoconductors. However cooling the photoresistor to 200 K requires over 5W of power.
A unique alternative to the currently available 10.6 micron radiation detectors is new generation of high speed, ambient temperature IR photoconductors [1-5], optimized for the best performance at 10.6 mm. The devices utilize photoconductivity (R005, PCI-L, MPC), photoelectromagnetic (PEM-L, PEMI-L) or photodiffusion effects (PDI-L). Their performance have been highly improved by the use of newly design quaternary HgCdZnTe narrow gap semiconductor structures with optimized composition and doping profiles. Recently we have developed unique monolithic optical immersion of active elements to CdZnTe hemi- or hyperhemispherical lens. The optical immersion increases detectivity by a large factor of 7 while bias power requirements are reduce by even larger factor of about 50. Housed in rugged packages of reduced size and weight. As it can be easily seen from the comparison of specifications, the uncooled VIGO's Model PCI-L-3 and PDI-L-3 photodetectors performance, similar to the conventional photoconductors cooled with four stage thermoelectric coolers which are recommended by Judson Infrared Inc., for CO2 Laser Warning Receivers.
Recently we have developed multispectral MPC photodetectors, with improved performance in wide spectral region 0.5-12 mm, designed specifically for Laser Warning Receivers.
The MPC series non-immersed photoconductors are characterized by the following unique features:
Due to short response times and excellent match for fast electronics they are ideal for pulsed and modulated laser application over wide frequency band. Custom devices such as single elements of various sizes, quadrant cells, multielement arrays, specialized packages, connectors, windows and optical filters are available upon request. The spectral detectivities can be tailored upon request, with increase of detectivity at short wavelength (0.6-4 mm) by two orders of magnitude. Optically immersed devices with performance additionally improved by a factor of 7 within wide spectral region of 1-12 mm are also available.
VIGO ambient temperature LWIR photodetectors are obviously not the BLIP detectors, but for the laser warning receivers their performance is high enough. They enable detection of such low power laser beams, which after reflection from the target, can not be detected by the searching system equipped with even the highest sensitivity detectors. So vehicles equipped with laser warning receivers, utilizing the Vigo's photodetectors, can move in the battle field without the danger of being spotted by the laser searching system. Thanks to minimal housing dimensions and minimal power consumption they can be mounted practically anywhere on the protected object or vehicle.
If for any reason the offered detector doesn't meet all your requirements we
would welcome the opportunity to assist you in selection and/or development of
the appropriate high performance detector for your applications.