Hertzian Dipole Measurements with InP Photoconductors

Abstract

In a recently described measurement scheme [1], the picosecond photoresponses of two radiation-damaged photoconductors were correlated by using these detectors as Hertzian dipoles, i.e., radiating and receiving dipole antennas. As in earlier microstrip circuit correlation experiments [2], one photoconductor is DC biased and acts as an electromagnetic pulse generator in response to excitation by a short optical pulse. The second photoconductor is biased by the electromagnetic transient from the first photoconductor, and functions as a sampling gate when excited by a second, delayed optical pulse. By monitoring the current induced in the circuit of the second photoconductor as a function of the delay between the optical pulses, the correlated photoresponse of the two circuits is measured. In Hertzian dipole experiments, a transient electromagnetic pulse from the pulse generator is radiated freely through a bulk dielectric to the second, receiving photoconductor. This results in a high pass coupling scheme, as opposed to the low pass transfer characteristics of microstrip interconnections.