Nondestructive waveguide loss-measurement method using self-pumped phase conjugation for optimum end-fire coupling

Abstract

We present a new nondestructive method for measuring the propagation loss coefficient in waveguides based on optimum end-fire coupling by self-pumped phase conjugation in a photorefractive BaTiO3 crystal. In a first pass through the waveguide, the laser beam is adapted to the waveguide mode profile, and hence the phase-conjugated beam is automatically coupled back into the guide with the optimum coupling efficiency. The propagation loss coefficient is determined by measurement of the transmittance of the phase-conjugated beam in the second pass through the wave-guide. We apply this method to measure the propagation loss coefficient of ion-implanted KNbO3 channel waveguides with an accuracy of better than 5%.