Paul P. Webb

Photon counting techniques with silicon avalanche photodiodes.

The properties of avalanche photodiodes and associated electronics required for photon counting in the Geiger and the sub-Geiger modes are reviewed. When the Geiger mode is used, there are significant improvements reported in overall photon detection efficiencies (approaching 70% at 633 nm), and a timing jitter (under 200 ps) is achieved with passive quenching at high overvoltages (20-30 V). The results obtained by using an active-mode fast quench circuit capable of switching overvoltages as high as 15 V (giving photon detection efficiencies in the 50% range) with a dead time of less than 50 ns are reported. Larger diodes (up to 1 mm in diameter) that are usable in the Geiger mode and that have quantum efficiencies over 80% in the 500-800-nm range are also reported.

Photon-counting techniques with silicon avalanche photodiodes

Silicon avalanche photodiodes (APD) have been used for photon counting for a number of years. This paper reviews their properties and the associated electronics required for photon counting in the Geiger mode. Significant improvements are reported in overall photon detection efficiencies (approaching 75% at 633 nm), and timing jitter (under 200 ps) achieved at high over-voltages (20 - 30 V). Results obtained using an active-mode fast quench circuit capable of switching over-voltages as high as 20 V (giving photon detection efficiencies in the 50% range), are reported with a dead-time of less than 50 ns. Larger diodes (up to 1 mm diameter), usable in the Geiger mode, which have quantum efficiencies over 80% in the 500 - 800 nm range also are reported.

Improved miniaturized HARLID for laser warning systems having high angular resolution

HARLIDTM is a digital approach to achieving angular sensitivity in a laser warning system. In this version of the HARLIDTM module, a number of improvements are described which correct for certain problems and limitations of earlier devices. The detector used is a 2-detector assembly, consisting of matching silicon and InGaAs arrays assembled in a sandwich configuration, to achieve spectral sensitivity between 500 and 1700 nm. Systematic angular readout errors observed in previous work have been avoided with the use of a new light-guide in which the optical channels are air instead of glass. Improved response time in the short wavelength end of the spectral range has been achieved with the use of thinner active regions in the elements of the silicon array, and a redesigned digital aperture mask significantly improves accuracy and reduces optical vignetting effects. The design and performance characteristics of a 6-bit HARLIDTM are presented.

Development of a modular suite demonstrator for two-band HARLID based on highly independent detection units and Ethernet communication

This article describes work that has been undertaken to develop a suite demonstrator for the evaluation of the digital High Angular Resolution Laser Irradiance Detector (HARLID). HARLID is a module designed to estimate the angel of arrival of a laser beam. It response to radiation ranging from 400 to 1700 nm and covers a 96 degree field of view (FOV) with a resolution of +/- 1 degree in a plane. The main goal of the suite demonstrator is to characterize new generations of HARLIDs and to provide means to evaluate new configurations in order to establish the requirements for the protection of military platforms with laser warning receivers (LWR). The suite demonstrator is a good example of how an Ethernet network can be used to share information between various senors over a specialized network. Moreover, it allows building and studying a plurality of configurations without regard to the separation and the structure between the detection units. To our knowledge, it is the first time that such as approach is used in the field of LWR.

Status of the development of the miniaturized digital High Angular Resolution Laser Irradiation Detectors (HARLID ) technology

Miniaturized digital HARLID modules integrating linear silicon and indium gallium arsenide arrays have been developed by the Defence Research Establishment Valcartier in collaboration with EG&G Optoelectronics Canada. These modules are designed to locate a laser source within +/- 1 degree(s) over a 90 degree(s) field of view either in azimuth or elevation. The principle of operation of these modules is based on the use of a Gray code mask to encode the angle of arrival of a laser beam. The performance of the 1-band HARLID has been recently investigated by the Laser Sensor Technology Laboratory, Wright-Patterson AFB, Dayton OH. The performance of a Laser Warning Receiver (LWR) integrating two 1-band modules has been successfully demonstrated in the laboratory and in the field. More recently the performance of this LWR has been evaluated at White Sands NM in desert conditions. Two-band HARLID modules have been recently fabricated by EG&G that makes use of a sandwich of Si and InGaAs detector arrays. The use of this configuration extends the spectral band from 400 to 1700 nm. Their E-O performance has been measured in the laboratory. The integration of HARLID modules with other sensors and through a Defensive Aids Suite is underway. Future plans of HARLID development have been established to enhance their E-O performance.

Miniaturized digital high-angular-resolution laser irradiation detectors (HARLID) for laser warning receivers (LWR)

A miniaturized digital 1-band HARLID module using linear silicon detector arrays has been developed. These HARLID modules, which fit inside standard TO-8 packages, were designed to locate angularly a pulsed laser source within plus or minus 1 degree over a 90 degree field of view either in azimuth or elevation. The principle of operation of this new patented-module is based on the use of a Gray code ask to encode the angle of arrival of a laser beam. The electro- optical (E-O) performance of this new module has been evaluated in the laboratory. A laser warning receiver (LWR) demonstrator integrating two of these modules has been built and its E-O performance measured in the laboratory and in a field environment aboard a tank. A new 2-band HARLID module now under development will include a sandwich of Si and InGaAs detector arrays and will extend the spectral band of the HARLID from 0.4 to 1.7 micron while increasing significantly its responsivity at 1.064 micrometer. A study of its technical characteristics and limitations has been recently completed and future HARLID technology development plan established.

High-speed 128-element avalanche photodiode array for optical computing applications

A high speed 128-element linear avalanche photodiode array, suitable for use in optical computing applications, has been designed and fabricated. The use of a guard ring surrounding the array results in low dark current and noise in the individual elements. Operation at gain 100 has shown good APD performance, with element dark currents less than 3 nA, noise less than 0.1 pA/Hz1/2, and rise and fall times about 1 ns. The design of the device makes it suitable for operation at frequencies up to 200 MHz. The paper includes the description of a solder bump mounting technique and multilayer substrate design which minimize capacitance between the elements, thereby maintaining low crosstalk. For further reduction of crosstalk, an alternative chip design is described in which a guard ring runs between all the elements.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.