Maskless photoencoded selective etching for glass-based microtechnology applications.

Two-photon excitation of carriers in boron E'-center-containing borosilicate glasses results in a photoencoding of selectively etchable regions. Using a turbulent etching process followed by polishing, we have demonstrated a number of patterning capabilities for microtechnology applications such as ultrafast capillary electrophoresis chips and rapid prototyping of diffractive optical elements.

Direct measurement of photoinduced charge distribution responsible for second-harmonic generation in glasses.

We have found that borosilicate glasses that produce second-harmonic generation after simultaneous irradiation by fields at omega and 2omega exhibit postexposure selective etching. We use the charge specificity of the selective etching process to spatially map the photoexcited electron distributions responsible for second-harmonic generation. The results show that nearly symmetric nondipolar charge distributions exist for some regimes of encoding and that, at higher intensities, a nearly dipolar distribution is produced.

Direct observation of the effective chi((2)) grating in bulk glasses encoded for second-harmonic generation.

The effective chi((2)) grating responsible for second-harmonic generation in bulk glasses was spatially resolved with a charge-selective etching technique. We observed a spatially varying structure with a period equal to the coherence length of the material. The measured period of the grating showed excellent agreement with the expected value. In addition, cross-sectional etching patterns show that in this regime of encoding intensities the f lux responsible for the intense electric field is not unidirectional as predicted by most models.

Photoimpulsive dispersive relaxation of the effective chi((2)) in binary lead-silicate glasses.

We have performed a detailed investigation of the readout decay of optically encoded second-harmonic generation in bulk lead-silicate glasses. The data show that over several decades of readout pulses, the relaxation is a stretched exponential in the pulse number. A new photoimpulsive dispersive transport model, in which the experimental data on the order of the optical process and the depth of the trap distribution below the mobility edge have been included, is used to explain the results.

Multiphoton micrometer-scale photoetching in silicate-based glasses.

Silicate-based glasses containing approximately 10% by weight boron or more have been observed to exhibit selective etching in hydrofluoric acid solution after direct exposure to intense visible laser light at 532 nm. The observation of a ring-shaped etch pattern in samples exposed to solid Gaussian beams suggests that selective etching is related to a charge-diffusion process rather than to local light-induced defect generation. The technique has so far resulted in the maskless production of micrometer-scale features with submicrometer depths.