We have measured the characteristics of a high-speed (10 MHz) quadrant avalanche photodiode (APD) in order to detect high frequency resonant oscillations and tip displacements of a cantilever. Currently, no high-speed quadrant detectors with a response bandwidth in the megahertz range are available, and experiments on the order of a few microseconds cannot be studied. A maximum gain of ~1500 and sensitivity of ~4.6 mV/μm were achieved at an optical power of 50 nW, using an optical spot diameter of 1.0 mm. We investigated the performance of the quadrant APD and measured the frequency response.
Citation: Applied Physics Letters
Pub Type: Journals
cantilever, AFM, quadrant, avalanche, photodetector, APD