Avalanche Photodiodes

An Avalanche Photodiode (APD) provides higher sensitivity than a standard photodiode. It is ideal for extreme low-level light (LLL) detection and photon counting. Offered in Silicon or InGaAs materials, these devices provide detectivity from 400 nm - 1100 nm. Multiple configurations are available to provide a wide range of sensitivity and speed options.

Products offered include:

• High-volume, cost effective silicon APDs for Range Finding and Laser Meter applications.
• Large area, UV-enhanced APDs for Molecular Imaging (PET).
• Long wavelength enhanced APDs for Analytical Applications.
• Multi element and quadrant APDs for Analytical Instruments.
• Standard, high performing APDs for Industrial applications.
• Hybrid Modules for easy implementation into high performing Instruments.

The use of APDs instead of PIN photodetectors will result in improved sensitivity in many applications. In general, APDs are useful in applications where the noise of the amplifier is high — i.e., much higher than the noise in the PIN photodetector. Thus, although an APD is always noisier than the equivalent PIN, improved signal-to-noise can be achieved in the system for APD gains up to the point where the noise of the APD is comparable to that of the amplifier. For example, when the system bandwidth is high, the amplifier noise is high, and an APD is likely to be useful. On the other hand, in very low bandwidth systems, the noise of the amplifier is likely to be very low, in which case, the APD may not be the best choice. In applications where the background optical power falling on the detector is very high, such as operation of the detector in daylight conditions with little or no filtering, an APD may not be useful, except perhaps at low gain, since the multiplied noise of the background illumination will be very high and may exceed that of the amplifier.