Optoelectronics

APD receivers achieve low noise without a TE cooler

4th February 2014
Nat Bowers
0

In order to reduce the overall noise of the detector/amplifier module, the capacitance connected to the amplifier has to be as small as possible. LASER COMPONENTS' H0 series of avalanche photodiode (APD) receivers make the connections as short as possible to make the parasitic capacitance as exceptionally low as the junction capacitance of the company's low-noise Silicon and InGaAs APDs (SARP-Series and IAG-Series).

The simplest way to use a detector is with a receiver circuit, where quality is judged according to the amount of noise produced. The company's Silicon and InGaAs APDs offer the optimal pre-requisites for detectors. But for the entire system, amplifier noise is the dominant source of noise.

When developing the H0 series of APD receivers, LASER COMPONENTS aim was to achieve low noise performance with high responsivity without the need for a thermoelectric (TE) cooler (with only a thermistor required for stability). Ideally, the inherent noise of the receivers should be zero. Although not physically possible, the company's developers came very close to meeting this goal.

Thanks to the compact, modified TO-5 housing with an approximate diameter of 5mm, the H0 series APD receivers can be integrated into small systems which measure distances or detect the smallest light signals.

If integrated with the company's SAR500 Si APD with a diameter of 500µm, the module has a noise equivalent power of just 4.86fW/√Hz at an amplification of 3x106V/W without requiring an expensive and power hungry TE cooler. If the receiver is intergrated with LASER COMPONENTS' IAG series 80µm or 200µm InGaAs APD, the module can achieve a noise equivalent power of 0.47pW/√Hz at an amplification of 1.1x106V/W.

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