Performance of 1mm² Silicon Photomultipliers

Thursday, May 01 2008

Applications

One application of SPM detectors is confocal microscopy. A confocal microscope uses fluorescence to image biological specimens. It uses a focused laser spot, which is scanned across the specimen, and a pinhole aperture located near the image plane to block fluorescent signals originating from regions of the specimen that are not under illumination by the laser spot. By eliminating the stray light, the image quality is improved but the amount of signal is reduced. As a result the photodetector used in confocal microscopes must be extremely sensitive and respond quickly to rapid changes in intensity. Silicon photomultipliers are an ideal photodetector for confocal imaging microscopes as they are fast, have single photon sensitivity, a peak optical response well matched to the emission wavelengths of the fluorescent probes, and low noise when cooled to moderate temperatures.

Additional applications for SPM detectors can be found in the areas of single photon counting, LIDAR, high-energy physics, homeland security, nuclear medicine, fluorescence detection, and in a multitude of other low-light applications where linear mode APD or PMT detectors are currently used.

For applications that require detection areas larger than 1mm², SPM detectors with a 9mm² active area are available. Arrays of SPM detectors can also be produced by flip chip bonding of detectors onto inexpensive glass or ceramic substrates⁵.

Summary

1mm² SPM detectors are sensitive to single photons at room temperature, provide photon number resolution, and have photon detection efficiency and dark rate performance similar to PMT detectors when cooled to the moderate temperatures attainable with thermo-electric coolers. In addition, SPM detectors have a number of advantages over PMT detectors, namely small size, low bias voltage operation, magnetic field insensitivity, and immunity to damage from exposure to ambient light conditions. SPM detectors can be used in single photon counting mode, pulse mode, and as an analogue detector. The SPMMini1020 has a peak PDE of 15.5% at 490nm and at 3V above the breakdown voltage has a dark count rate of the order of 600kcps at -20°C.

This article was written by Dr. Andrew G. Stewart, Design Engineer, SensL (Cork, Ireland). For more information, contact Mr. Padraig Hughes at This e-mail address is being protected from spambots. You need JavaScript enabled to view it , or click here.

References

1. A. G. Stewart, V. Saveliev, S. J. Bellis, D. J. Herbert, P. J. Hughes, J. C. Jackson, Performance of 1mm² Silicon Photomultipliers, IEEE J. Quantum Electron., Vol. 44, No. 2, pp. 157, Feb 2008

2. V. Golovin and V. Saveliev, Novel type of avalanche photodetector with Geiger mode operation, Nucl. Instr. Meth. A, vol. 518, pp. 560-564, 2004

3. J. C. Jackson, Silicon Photomultiplier Detectors for Low Light Detection, Photonics Spectra, Dec 2007

4. J. O’Keeffe and J. C. Jackson, Laser Focus World, Jan 2006

5. P. J. Hughes, D. Herbert, A. Stewart, J. C. Jackson, Tiled Silicon Photomultipliers for large area, low light sensing applications, Proc. Of SPIE: Semiconductor Photodetectors IV, Vol. 6471, 2007