December 12, 2006, Geneva, Switzerland--A single-photon counter with adjustable efficiency up to 25% (controlled by adjusting the bias voltage) will be demonstrated by id Quantique at the coming BIOS and Photonics West exhibitions (January 20-25, 2007; San Jose, CA).The efficiency is adjustable to optimize it for specific applications.
With calibration done at 1550 nm, the counter (called the "id201") allows efficiency adjustment to four preset values--10%, 15%, 20% and 25%--as well as a mode where the bias voltage can be smoothly scanned. The module covers the range between 900 and 1700 nm. With a 25% detection efficiency, the id201 is the world's most sensitive near-IR single-photon-detection product, says the company. Like all single-photon detectors based on an indium gallium arsenide/indium phosphide avalanche photodiode, the device works in gated mode. A voltage pulse is applied on the photodiode to reverse-bias and activate it. Five different gate widths (2.5, 5, 20, 50, or 100 ns) can be chosen; alternatively, the gate width can be continuously scanned between 0 and 20 ns.
The maximum trigger frequency has been increased from 4 to 10 MHz. The electronics also perform active quenching after avalanche sensing to keep afterpulsing levels low, even at long gate widths. For further afterpulsing reduction, a deadtime feature can be used to blank gates for a certain time after an avalanche. With the adjustable delay (which permits moving the bias gate by up to 25 ns in steps of 100 ps), synchronization with the optical signal is straightforward.
The device's avalanche photodiode used at the heart of the id201 meets Telcordia GR-468-Core reliability criteria and is available with a single-mode (SMF28) or multimode (50/125 micron step-index) fiber-optic input. The module includes internal counters, a display to monitor their values, and an RS-232 interface. Applications include quantum optics, quantum cryptography, fiber-optic characterization, spectroscopy, single-photon-source characterization, eye-safe laser ranging (lidar), and failure analysis of electronic circuits. The id201 will be available at the end of 2006.