Surface‐emitting second‐harmonic generator for waveguide study

A novel surface emission of coherently generated second‐harmonic wave is reported for the first time.The technique is used for the observation of the difference in propagation constant of the TE0 and TM0 mode of GaAs/AlGaAs waveguide cavity to a high degree of accuracy. In this technique the second‐harmonic signal propagates out from the top surface of the waveguide structure, converting the modal phase difference between TE0 and TM0 modes into intensity variation along the waveguide length. The second‐harmonic signal is easily observable by the naked eye, and the technique does not require wavelength tuning or mechanical movement for the measurement of birefringence.