a b s t r a c tWe report the fabrication and characterization of a Ti 4 þ : Tm 3 þ : LiNbO 3 optical waveguide in view of photon-echo quantum memory applications. Specifically, we investigated room-and cryogenictemperature properties of the waveguide, and the Tm 3 þ ions, via absorption, spectral hole burning, photon echo, and Stark spectroscopy. For the Tm 3 þ ions, we found radiative lifetimes of 82 ms and 2.4 ms for the 3 H 4 and 3 F 4 levels, respectively, and a 44% branching ratio from the 3 H 4 to the 3 F 4 level.We also measured an optical coherence time of 1:6 ms for the 3 H 6 2 3 H 4 , 795 nm wavelength transition, and investigated the limitation of spectral diffusion to spectral hole burning. Upon application of magnetic fields of a few hundred Gauss, we observed persistent spectral holes with lifetimes up to seconds. Furthermore, we measured a linear Stark shift of 25 kHz cm=V. Our results are promising for integrated, electro-optical, waveguide quantum memory for photons.

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We propose an optical encryption technique where the encrypted field and the decrypting key are obtained by three-step phase-shifting interferometry and registered as digital Fresnel holograms in a joint transform correlator architecture. Decryption can be achieved by digital or optical means. The technique allows the complete process to be achieved at high speed and data to be transfered via digital communication channels. Experimental implementation is performed in a system based on a programmable liquid-crystal TV display working in pure phase mode to represent the input data and to introduce the required phase shifts. A CCD is used to register the output data.

Determination of the intrinsic quality factor of a loaded whispering gallery mode microcavity can be important for many applications where the coupling conditions cannot be tuned. We propose a single-scan technique based on a Stokes parameters analysis to extract the intrinsic quality factor and therefore determine the coupling regime. We propose a simple model for this analysis and present experimental measurements, which are in very good agreement with the model.

In this work we propose a new robust optoelectronic scanning system for scanning microscopy. The device is based on a programmable liquid crystal television display (LCTV) that acts as a pixel-by-pixel controlled pure phase spatial light modulator. The computer addressed liquid crystal screen allows synthesize different diffractive optical elements at video rates. The phase shifts introduced by these elements make possible a complete control over the position and focusing of the scanning beam. Ó 2004 Published by Elsevier B.V.