Unique APD drives four-channel photon counter

Citation

(2006), "Unique APD drives four-channel photon counter", Sensor Review, Vol. 26 No. 4. https://doi.org/10.1108/sr.2006.08726daf.004

Unique APD drives four-channel photon counter

Unique APD drives four-channel photon counter

Keywords: Optoelectronic devices

Pacer components, a leading optoelectronic solutions provider, has announced the availability of the four-channel single photon counting module (SPCM) from PerkinElmer using the unique SLIKe silicon avalanche photodiode (APD). This high quality module enables measurement of very low power optical sources for applications such as single molecule detection, high throughput DNA sequencing, LIDAR, photon correlation spectroscopy, astronomical observation, optical range finding, adaptive optics, ultra sensitive fluorescence and particle sizing (Plate 3).

Plate 3 At the heart of the four-channel SPCM-AQ4C, PerkinElmer's unique silicon APD boasts a detection efficiency exceeding 60 per cent at 650nm

The SPCM-AQ4C is a SPCM, providing four independent channels capable of detecting single photons with energy levels equating to wavelengths from 400 to 1,060nm. At the heart of the design, the SPCM uses PerkinElmer's unique silicon APD (SLIK™) which has a circular active area boasting a peak photon detection efficiency exceeding 60 per cent at 650nm.

SLIK™ APDs are unique because of their extremely-low bulk leakage current in the dark. There are two reasons for the high single-photon detection efficiency of PerkinElmer's SPCM. First, the silicon-based detector exhibits high quantum efficiency from the UV to the near- infrared. Secondly, by operating sufficiently high above the breakdown voltage, nearly all generated electrons will induce a junction breakdown that results in a detectable pulse. This method of operating the detector above the breakdown voltage is called the Geiger mode. It uses a “quench and reset” cycle process that takes only about 45ns thus enabling rapid detection of many photoelectrons.

Each photodiode is both thermoelectrically cooled and temperature controlled, ensuring stabilised performance despite changes in ambient temperature. Each of the APDs is a self-contained module with integrated electronics. The SPCM card uses an improved circuit with a peak count rate greater than 4 Mcycle/s for short bursts of time on all four channels, and a count rate of 1.5 Mcycle/s for continuous operation. The output of each channel is a TTL pulse of 25ns with 50ns dead time, for each single detected photon. All input and output signals are available at the card connector at the rear of the module.

Each channel input is gated, a useful feature for the measurement of signals which appear over a small time period and for reducing signal-to-noise ratio when background flux levels are greater than the signal. For this application, the gate is opened only when the light signal is present. The probability of afterpulsing, where a pulse is output falsely after a photon has been detected, is only 0.5 per cent maximum, with a more typical value of 0.3 per cent. The dark count per channel is specified as 500 counts per second.

With its modular design, the four- channel SPCM can be stacked to create 16-channel arrays and beyond. With the compact size of the four-channel SPCM, systems with 100 channels or more are achievable, allowing for the collection of multiple parameters. This “plug-and-play” system is also simple to use – only requiring the connection of power supply voltages. The inputs use FC fibre-optic receptacles which are optically aligned to the APD. Several fibre optic patch cord options are available from Pacer.

For further information, visit the web site: www.pacer-components.co.uk/