Homodyne detection of second-harmonic generation as a probe of electric fields

We demonstrate and analyze a new method for probing electric field strengths using optical second-harmonic generation. The technique, based on a homodyne detection scheme, employs interference between the field-induced second-harmonic radiation from the sample and strong second-harmonic radiation from a reference. The scheme provides a linear relationship between the measured second-harmonic signal strength and the amplitude of the electric field being probed, thus providing easy calibration of the amplitude of the electric field and direct information on its sign. Experimental results are presented for direct and homodyne detection of in-plane fields in silicon structures. A discussion of the expected signal-to-noise characteristics is presented and the results are compared to experimental findings. Homodyne detection of electric fields with strengths on the order of 100 V/cm can be achieved with reasonable integration times.