Two-color holography in reduced near-stoichiometric lithium niobate.

We explored a number of factors affecting the properties relevant to holographic optical data storage by using a two-color recording scheme in reduced, near-stoichiometric lithium niobate. Two-color, or photon-gated, recording is achieved by use of 852-nm information-carrying beams and 488-nm gating light. Readout at 852 nm is nondestructive, with a gating ratio of ~10(4).

Digital holographic storage system incorporating optical fixing.

Digital holograms have been written in stoichiometric Pr:LiNbO(3) in a two-color recording scheme, demonstrating what is to our knowledge the first all-optical nondestructive readout of digital data. Using writing light at 800nm and gating light at 476 nm, we stored and retrieved 256-kbit digital data pages with a raw bit-error rate BER of <10(-4) .

Intensity dependence and white-light gating of two-color photorefractive gratings in LiNbO(3).

Photorefractive gratings have been written in Pr:LiNbO(3) by use of a diode laser for writing and of filtered white light (390-520nm) as a gating source. The gating light increases the writing efficiency by more than 3 orders of magnitude, and the two-step writing process provides nondestructive readout. The material sensitivity for two-color writing rises strongly for gating wavelengths near the bandgap and approaches that of Fe-doped lithium niobate at power densities of a few watts per square centimeter.

Penetration of radiopaque dental restorative materials using a novel ultrasound imaging system.

Purpose: To determine whether a novel ultrasound imaging system could detect 25 microm thick cracks beneath gold, silver amalgam, and porcelain restorations on tooth phantoms.

Methods: Tooth phantoms were constructed using acoustically-matched composite to simulate dentin, with 25 microm thick water-filled cracks located approximately 1 mm inside the simulated dentin. Porcelain and gold restorations were bonded using resinous cement, and an amalgam restoration was attached using mechanical retention.

Ultrasound crack detection in a simulated human tooth.

Objective: Currently, diagnosis of cracked teeth generally depends upon the overall clinical assessment, or on exclusion of other clinical possibilities, not primarily on the direct identification of cracks themselves. Owing to its short wavelength in hard tissues and associated high resolution, ultrasound has the potential to allow detection of cracks within tooth structure. However, ultrasound detection of dental cracks has not previously been achieved.