Sensitive measurement of optical nonlinearity using an absorptive phase object

We report on a modified nonlinear optical measurement technique using an absorptive phase object (PO) to characterize weak optical refraction nonlinearities. The absorptive PO consists of a circular silica substrate on which a dielectric plate has been deposited. The inner dielectric plate simultaneously introduces a π/2 phase shift and changes the amplitude of the incident light. We demonstrate that the measurement sensitivity can be enhanced with the transmittance of the absorptive PO. Experimental and simulation results are presented to validate our approach.