The response of a vacuum photoemissive photodiode to a light beam has been investigated as a function of the angle of incidence in order to check whether the response is always proportional to the absorbed number of photons. By working mainly in the region of total internal reflection and measuring the reflected beam with an auxiliary detector at near-normal incidence, we were able to determine the absorptivity and to compare it with the measured photoelectric current. We found that the ratio of the two quantities is constant and independent of the angle of incidence for TE waves but not for TM waves. The results suggest that there exists an extra loss mechanism for TM waves, which may be connected with plasmon generation. Because of this extra loss, the response of the detector to TM waves is not a direct measure of the number of absorbed photons.
© 1988 Optical Society of America
Original Manuscript: December 7, 1987
Revised Manuscript: February 19, 1988
Published: June 1, 1988
T. H. Chyba and L. Mandel, "Angular sensitivity of a vacuum photodiode, or does a photodetector always count absorbed photons?," J. Opt. Soc. Am. B 5, 1305-1311 (1988)