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Balanced homodyne detection technique for surface nonlinear optics

In this paper, we present an ac optical balanced homodyne detection system which enables us to detect both the amplitude and phase of the surface optical nonlinear signal. In this system, a balancing scheme and an unique lock-in detection method using fundamental interference signal as a reference has been employed. This system enables us to simultaneously measure, with extremely high sensitivity of 3 aW and high precision, both the intensity and phase of a very weak surface SHG signal. Experimental results of simultaneous measurement of the intensity and phase in surface second-harmonic waves generated from native-oxidized Si (111) surfaces is presented.