Discrete diffraction in optically-induced real-time waveguides in photorefractives

Summary form only given. We report the experimental observation of all-optical discrete diffraction, in which both the waveguide array and propagating wavefunction are generated optically. The waveguides are induced optically, in real-time, by illuminating a photorefractive crystal with an interference grating. We demonstrate discrete diffraction in a 1D array of 1D waveguides, and subsequently optical guidance in a 2D array of 2D waveguides. In our experiments, we use a 6 mm long SBN-75 crystal, chosen for its strong dielectric anisotropy. The 1D array is created by interfering ordinarily polarized light through a Mach-Zehnder interferometer, while the signal beam is extraordinary light focused to couple into one waveguide. Voltage applied against the c-axis helps increase the depths of the potential wells ("sharpens" the waveguide array). The 2D array is created by increasing the applied voltage and allowing the 1D waveguides to break from transverse (modulational) instability.