This new approach to optical waveform measurement is based on linear optical sampling: a short optical pulse provides the gating function and the sampling is accomplished using coherent homodyne mixing on a low speed photodetector, a linear optical process. The phase sensitivity inherent to homodyne detection is removed by simultaneous measurement of orthogonal phase quadratures, and the combination of ultrafast optical gating with linear homodyne detection and low speed optoelectronics enables high temporal resolution with sensitivities over 1000x greater than comparable nonlinear optical techniques.
U.S Patent No. 7,529,481