Yu-Ta Wang

Ce3+:YAG double-clad crystal-fiber-based optical coherence tomography on fish cornea.

A Ce(3+):YAG double-clad crystal fiber (DCF) visible emission was used as the light source for optical coherence tomography (OCT). The visible emission was produced from a 10 microm core DCF pumped by a diode laser. The broadband emission and short central wavelength of this light source enabled the realization of 1.5 microm axial resolution in air. The relatively clean spectrum reduced the side lobe of its point-spread function, and therefore facilitated the generation of a high-quality image with less crosstalk between adjacent image pixels. As a demonstration, an Aplocheilus lineatus goldfish was experimented on to map out the stroma of its cornea. This visible-light-based OCT can be utilized for industrial inspection as well as ocular applications.

Cell death detection by quantitative three-dimensional single-cell tomography.

Ultrahigh-resolution optical coherence tomography (UR-OCT) has been used for the first time to our knowledge to study single-cell basal cell carcinoma (BCC) in vitro. This noninvasive, in situ, label-free technique with deep imaging depth enables three-dimensional analysis of scattering properties of single cells with cellular spatial resolution. From three-dimensional UR-OCT imaging, live and dead BCC cells can be easily identified based on morphological observation. We developed a novel method to automatically extract characteristic parameters of a single cell from data volume, and quantitative comparison and parametric analysis were performed. The results demonstrate the capability of UR-OCT to detect cell death at the cellular level.

The study of temperature dependence of photoresponse in superlattice infrared photodetectors

Temperature dependence of the photoresponse in two superlattice infrared photodetectors with different single barriers is studied. It is found that the short-wavelength response decreases with temperature, but the long-wavelength one increases. The crossing point of those two response ranges is independent of temperature. The movement of its associated wavelength under different biases is investigated and analyzed. The relevant physical mechanisms are found and integrated into a simple model to explain the experimental results. Based on the model, another sample with a superlattice integrated with multiple quantum wells is designed to demonstrate whether its temperature dependence of the photoresponse is consistent with our understanding. The sample indeed shows a broadband response which enhances with temperature in all wavelengths.

Mirau-based full-field time-domain optical coherence tomography using Ce3+:YAG crystal fiber light source

Based on single-objective construction utilizing high brightness Ce3+:YAG single-clad crystal fiber light source, this Mirau-based full-field time-domain optical coherence tomography with circular polarization incident light represents deeper penetration in scattering medium. Using objective-changeable ability of home-designed Mirau objective, this system provides different applications, like biological tissue and single cells, by different spatial resolution with corresponding dynamics. High quality image relying on less ghost image and near common-path interference was demonstrated under this compact and power-stable system.

In vivo 3-D cellular level imaging using Mirau-based full-field optical coherence tomography on skin tissue

With silicone-oil-immersion Mirau objective utilizing high brightness Ce3+:YAG crystal fiber light source through multi-mode fiber, this system respectively images in vivo tomographic cellular structure of tissue and flowing pathway of red blood cell in dynamics.

Discrimination of Keratinocytes and Fibroblasts by Parametric Single-cell Tomography

We report using ultrahigh-resolution optical coherence tomography for distinguishing keratinocytes and fibroblasts at the single-cell level. Linear discriminant analysis based on characteristic parameters extracted from volume data was applied for the prediction of cell types.

Numerical dispersion compensation for optical coherence tomography on 3D microstructure

A vertically aligned liquid crystal display panel was inspected with an optical coherence tomography system. The in-depth signal dispersion was numerically compensated so that high axial resolution can be maintained throughout the 3D microstructure.

Ultrahigh resolution optical coherence tomography using Cr 4+ :YAG fiber

Using a CW 265-nm broadband source from Cr⁴⁺:YAG double-clad fiber, ultrahigh resolution optical coherence tomography was demonstrated with a 73-dB S/N ratio. A 3-µm TiO<inf>2</inf> thin film was used to verify its 3.5-µm axial resolution.

Low-voltage operation photodetector made by coupling superlattice and quantum wells

We have investigated a novel photodetector structure of coupling superlattice and quantum wells. This device can be operated at low bias range and even the photovoltaic mode. The broadband response is achieved by this structure.