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As a major component of the connective tissues, collagen fibers are responsible for various physiological functions inside the body. They provide support for the skin, partial focusing through the cornea, and coordinate movements via tendons, ligaments, and cartilages. In many medical procedures, thermal reorganization of the collagen structure is inevitable or desired. Therefore, the optimization of the therapeutic values of these procedures requires the characterization of thermal changes to collagen fibers. In this presentation, we use multiphoton microscopy to achieve this task. We will show that second harmonic generation (SHG) microscopy can characterize the thermally altered states of collagen and that they have potentials to be used in imaging applications in vivo.

Atherosclerosis is unquestionably the leading cause of morbidity and mortality in developed countries. In the mean time, the worldwide importance of acute vascular syndromes is increasing. Because collagen fiber is a critical component of atherosclerotic lesions; it constitutes up to 60% of the total atherosclerotic plaque protein. The uncontrolled collagen accumulation leads to arterial stenosis, whereas excessive collagen breakdown weakens plaques thereby making them prone to rupture finally. Thus, in this study, we present the first application, to our knowledge, of using polarization-sensitive optical coherence tomography (PS-OCT) in human atherosclerosis. We demonstrate this technique for imaging of intensity, birefringence, and fast-axis orientation simultaneously in atherosclerotic plaques. This in vitro study suggests that the birefringence change in plaque is due to the prominent deposition of collagen according to the correlation of PS-OCT images with histological counterpart. Moreover, we can acquire quantitative criteria based on the change of polarization of incident beam to estimate whether the collagen synthesized is "too much" or "not enough". Thus by combining of high resolution intensity imaging and birefringence detection makes PS-OCT could be a potentially powerful tool for early assessment of atherosclerosis appearance and the prediction of plaque rupture in clinic.

We studied the photoreflectance (PR) and photoluminescence (PL) spectroscopies of self-assembled InAs quantum dots grown on n+-GaAs (100) by molecular beam epitaxy. The PL spectroscopy of self-assembled Ge quantum dots (Ge-QDs) grown on n+-Si (100) by metal organic chemical vapor deposition epitaxy was also investigated. PL spectra show the optical transitions from the ground state and excited states in the InAs quantum dots (InAs-QDs) and a transition from the ground state in the Ge-QDs at the temperature 20 K. PR spectra show the energy features of the transitions of the ground state and four excited states in the InAs-QDs, InAs wetting layer, and GaAs band-gap. The fitted results of the transition energies and the broadening parameters are reported. The results demonstrate that low growth rate of the InAs-QDs, the submonolayer deposited of the alternating beam, and covered with the overgrowth InGaAs methods, have improved the nano-structure quality of the InAs-QD, grown at 485¦C and V/III ratio of 2. The high quality Ge-QDs were made, and characterized by PL experiments.© (2003) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Endoscopy is a versatile medical device, but with deficiency of severe image distortion from a super-wide angle lens CCD- camera installed. We designed a planar circular pattern target mounted on a XYZ transnational stage and developed a calibration method to correct the distorted image. Through the image shaping similarity and symmetric properties of a circular pad posing in the specific spatial coordinates, an optimized algorithm is to adjust the orientation of the gastroscopic head and the coordinates of the target until the accurate system alignment obtained. The profiles of image mapping and the calibration object are to derive both the image distortion and calibration function as single variable polynomial equations. Using the calibration function, the distorted gastroscopic image could transfer to comply with an ideal pinhole mapping. The experimental results validated that a gastroscopic image could be corrected and depict better geometrical information. Concurrently displaying with the traditional screen, this technique could aid the physician in metering a tumor or lesion size.

Temperature dependence photoreflectance has been used to study InAs/GaAs self-assembled quantum dots (QDs). The QDs samples were grown on (100) misoriented 7 degrees toward (110) GaAs semi-insulting substrate by a gas source molecular beam epitaxy with changing V/III ratio. The energy features of PR spectra from QDs and wetting layer (WL) were fitted by the first derivative Gaussian functional form and band-gap feature was fitted by the derivative-like Lorentian line shape function.THE blue-shift of optical transition energies responded from QDs has been characterized. The signals responded from an ultra-thin wetting layer of InAs/GaAs QDs samples and band-gap transition energy from GaAs portions were also observed. It demonstrates that the energy features of PR spectrum responded form QDs and WL section could provide the important information about QDs quality. The results show that the size, uniformity and density of QDs can be improved by the changing V/III ratio.

The electrolyte electroreflectance and reflectivity measurements were used to study the etching process and analyze the etching mechanism of etched anodic oxide film on HgCdTe. The observed shift of the energy peak in reflectance spectrum can be explained by the surface roughness. It was found that the oxide etched by HCl or HNO3 does not recover the original reflectivity spectra due to the surface characteristics, but lactic acid does. The multiple reflection theory was used to calculate the thickness and the etching rate of the oxide film. The etching characteristics of lactic acid have also been studied for different concentrations.

of Electrical EngineeringTaipei, Taiwan, Republic of ChinaFeng-Yuh Juang, Tin-Fung Chang and Jia-Song WuChung-Shan Institute of Science and TechnologyLung-Tan, Taiwan, Republic of ChinaABSTRACTElectrolyte electroreflectance (EER) is used to investigate the near surface properties of HgCdTe. Weused the technique of EER coupled with electrochemical etching to study the characteristics of HgCdTe.Annealing of B ion-implanted HgCdTe with ZnS encapsulation and anode sulfide film is studied. Theresults of fitting parameters show that a highly disordered surface layer exists after implantation, and anobvious recovery occurs after the sample is annealed at 2000 C It also shows that there are no obviousimprovements when the sample is annealed at 3000 C. The sample encapped with CdS film is better thanuncapped CdS film. We found that the composition of Cd at the surface changes due to the chemicalinteraction of anode sulfide film. It also shows that the sulfide active CdS film can improve the adherenceof ZnS to the MCT substrate and make the sample more stable.

The excitonic photoreflectance (PR) spectra of GaAs/A1GaAs multiple quantum wells, grown by the molecular beam epitaxial (MBE) technique, were investigated at oblique and near-normal incident angle with different polarized probe lights. The PR spectra have been measured at room temperature using He-Ne laser as a pumping beam in order to study the variations of the spectral line shapes. The experimental results show that the usefulness of the electromodulation to characterize the microstructure of the substrate may be enhanced if we take in account the polarization state of the probe light which is incident at larger oblique angle. The PR spectra were fitted by a third order derivative functional line shape, thus making it possible to determine the energy band gap, broadening parameters, amplitudes, and the phases of the spectral features precisely.