Hwan Hong Lim

Measurement of refractive index and thickness of transparent plate by dual-wavelength interference.

We developed an accurate and efficient method for measuring the refractive indices of a transparent plate by analyzing the transmitted intensity versus angle of incidence. By using two different wavelengths, we resolved the 2pi-ambiguity inherent to the phase measurement involving a thick medium, leading to independent determination of the absolute index of refraction and the thickness with a relative uncertainty of 10(-5). The validity and the accuracy of our method were confirmed with a standard reference material. Furthermore, our method is insensitive to environmental perturbations, and simple to implement, compared to the conventional index measurement methods providing similar accuracy.

Nondestructive quality evaluation of periodically poled lithium niobate crystals by diffraction

We derived an expression for the noise between the diffraction orders from a random grating. The result was applied to analyze the statistical duty-cycle error in PPLN, providing an efficient means for poling quality evaluation.

Measurement of Refractive Index of Solid Medium by Critical Angle Method When Air Gap is Present

A critical angle method was used to measure the index of refraction of a solid medium when an air gap between the prism and the medium is present. The gap effect was analyzed both numerically and experimentally. Since the total internal reflection is severely disturbed by the large gap, determination of the critical angle and the resulting refractive index becomes ambiguous and inaccurate. By using an index matching fluid, we could determine the index of refraction with an uncertainty of

Quality evaluation of quasi-phase-matched devices by far-field diffraction pattern analysis

{\pm}2{\times}1^{-3}

Determination of refractive index of transparent plate by Fabry-Perot fringe analysis

even when the gap is as large as 1

Observation of standing light wave by using fluorescence from a polymer thin film and diffuse reflection from a glass surface: Revisiting Wiener’s experiment

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Nondestructive quality evaluation of periodically poled lithium niobate crystals by diffraction-noise measurement

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Analysis of periodically poled domains of lithium niobate crystal by diffraction

Periodically poled ferroelectric crystals form highly efficient quasi-phase matched optical frequency conversion devices. For optimal performance of such devices, accurate period and duty-cycle are required throughout the poled region. For the quality evaluation we demonstrate a simple and a powerful technique using far-field diffraction measurement. Periodically poled lithium niobates were fabricated and etched out to reveal a surface-relief grating. The far-field diffraction pattern was analyzed to obtain statistical information for the duty-cycle. We explored the equivalence between the linear diffraction experiment and the conventional second-harmonic generation method for poling quality evaluation, through the Fourier-transform of the spatial modulation of domains.

Determination of refractive indices of optical wafers by interferometric method

We developed a simple and accurate method for measuring the refractive indices of transparent plates by analyzing the transmitted fringe pattern as a function of angle of incidence. By using two different wavelengths, we resolved the 2π- ambiguity inherent to the phase measurement involving a thick medium, leading to independent determination of the absolute index of refraction and the thickness with a relative uncertainty smaller than 10-5 for a 1 mm-thick fused silica plate. The accuracy of our method was confirmed with a standard reference material.

Accurate Measurement of Refractive Indices of Optical Wafers by Using Fabry-Perot Type Interference

In 1892 Drude and Nernst reported the first observation of a standing light wave by using a fluorescent thin film, which is a real-time version of Wiener’s first experiment on standing light wave. We reproduce the experiment by Drude and Nernst with improved efficiency using modern laser technology and a highly fluorescent π-conjugated polymer. We also used a glass plate scratched slightly on one surface to visualize the same phenomenon using diffuse reflection instead of fluorescence. This method has the advantage of being a wavelength-independent observation compared to the fluorescence method.