Abstract

A new type of optically encoded, optically readable, high-density information storage has been demonstrated in commercially available silicate glass. The effect is based on optically encoded second-harmonic generation (SHG) in glass. Information is stored in the form of wavelength selective, one dimensional χ⁽²⁾ gratings within the glass and is read out by illuminating the encoded area with light at designated wavelengths. During the encoding process, the glass evolves in time to produce SHG with efficiencies greater than seven orders of magnitude above the initial values. It has been shown that the SHG occurs via a frozen-in χ², which oscillates as cos(Δkz), where z is the beam propagation direction and Δk = k(2ω) - 2k(ω) is the wavevector mismatch between the fundamental and second-harmonic beams. For a sample encoded with ω_o, ω_o/2), the SHG as a function of readout frequency, ω, varies as:

© 1993 Optical Society of America