Non-invasive characterization of the domain boundary and structure properties of periodically poled ferroelectrics.

Shaping the ferroelectric domains as waveguide, grating, lens, and prism are key to the successful penetration of periodically-poled ferroelectrics on various wavelength conversion applications. The complicated structures are, however, difficult to be fully characterized, especially the unexpected index contrast at the anti-parallel domain boundaries are typical in the order of 10(-4) or less. An ultrahigh resolution optical coherence tomography was employed to fully characterize the domain boundary and structure properties of a periodically-poled lithium niobate (PPLN) waveguide with an axial resolution of 0.68 µm, an transversal resolution of 3.2 µm, and an index contrast sensitivity of 4x10(-7). The anti-parallel domain uniformity can clearly be seen non-invasively. Dispersion of the ferroelectric material was also obtained from 500 to 750 nm.

Microstructural and microspectral characterization of a vertically aligned liquid crystal display panel.

The microstructural and microspectral characteristics of a vertically aligned liquid crystal display (VA-LCD) panel were obtained noninvasively for the first time. With 1 µm axial and 2 µm transversal resolutions, the cell gap profile beneath the patterned thin-film transistor of the VA-LCD panel can clearly be resolved. The thicknesses of the multiple thin-film layers and the embedded defects can also be unveiled. As far as spectral response is concerned, the light transmittance at the layer boundaries can be estimated from the measured reflectance, which is crucial information for the design of a highly transmissive panel. The color shift of the VA-LCD panel due to fabrication error was evaluated.

Multipass acoustically open photoacoustic detector for trace gas measurements.

What we believe to be a novel multipass, acoustically open photoacoustic detector designed for fast-response, high-sensitivity detection of trace gases and pollutants in the atmosphere is demonstrated. The acoustic pulses generated by the absorption of the light pulses of a tunable optical parametric oscillator by target molecules are detected by an ultrasonic sensor at 40 kHz. The photoacoustic signal is enhanced by an optical multipass arrangement and by concentration of the acoustic energy to the surface of the ultrasonic sensor. The detection sensitivity, estimated from CO2 measurements around a 2 microm wavelength, is approximately 3.3 x 10(-9) W cm(-1).