Genichi Kanai

Microlenses and microlens arrays formed on a glass plate by use of a CO 2 laser

Microlenses and microlens arrays were formed directly on a surface of a glass plate by use of a CO(2) laser. When the surface of a glass plate is heated locally to a working point of the glass material by use of a focused CO(2) laser beam, it tends to become a hyperboloid owing to surface tension, which results in a microlens. A profile of the microlens was measured with an ultrahigh accurate three-dimensional profilometer (Model UA3P, Matsusita Electric Industrial Company Ltd.) that utilizes a specially designed atomic force microscope. An intensity profile and a spot diameter at the focus of the microlens were measured with a microscope and a CCD system utilizing a He-Ne laser as a light source. The focused spot FWHM diameter of 1.35 mum was obtained, and the modulation transfer function was derived from the spot profile. Microlens arrays were also fabricated and characterized.

In Vivo Raman Study of the Living Rat Esophagus and Stomach Using a Micro-Raman Probe under an Endoscope:

A small endoscope system equipped with a micro Raman probe is developed for in vivo Raman measurements in living rats. The measurements are done under anesthesia and artificial respiration to minimize the impact on the rats. Raman spectra of living rat esophagus and stomach are successfully measured. Our results suggest that the Raman spectra reflect subsurface tissue structure that cannot be distinguished in the endoscope image. After the experiments, rats recover without any aftereffects. It is verified that the Raman measurement using the present system is safe and noninvasive for rats.

Detection of ER stress in vivo by Raman spectroscopy

The endoplasmic reticulum (ER) is an organelle in which most membrane and secretory proteins are synthesized. If these proteins are not folded correctly, unfolded proteins accumulate in the ER lumen, causing a cellular situation known as ER stress. Recently, many studies on the relationship between ER stress and diseases have been reported. Thus, studies of ER stress in vivo should yield information that is useful in pathology. Model mice have been developed as a powerful tool to visualize ER stress in vivo, but this approach depends on transgenic technology. Here, we report on a method of detecting ER stress in vivo by Raman spectroscopy. Our experiments revealed that two specific Raman bands were reduced in both cultured cells and animal tissues in an ER stress dependent manner. This suggests that Raman spectroscopy could be a useful tool to detect ER stress in vivo without transgenic technology.

Fabrication of hollow waveguides for CO 2 lasers

Germanium-coated metal (silver, gold, and copper) hollow waveguides for CO(2) laser energy delivery have been fabricated by electron-beam evaporation and plating techniques in which an acid-soluble glass mandrel with small surface roughness was used. The transmission characteristics of Ge-coated metal hollow waveguides were studied. Ge-coated Ag hollow waveguides showed smaller loss, 0.2 dBm, for CO(2) laser light than Ge-coated Au and Cu waveguides. The transmission characteristics of Ge-coated Ag hollow waveguides were measured in relation to a core diameter and a bending radius.

Application study of the optical biopsy system for small experimental animals

An optical biopsy system for small experimental animals has been developed. The system includes endoscope probe, portable probe and two kinds of miniaturized Raman probes. The micro Raman probe (MRP) is made of optical fibers and the ball lens hollow optical fiber Raman probe (BHRP) is made of hollow fiber. The former has large focal depth and suitable to measure average spectra of subsurface tissue. The latter has rather small focal depth and it is possible to control focal length by selecting ball lens attached at the probe head. It is suitable to survey materials at the fixed depth in the tissue. The system is applied to study various small animal cancer models, such as esophagus and stomach rat models and subcutaneous mouse models of pancreatic cancers. In the studies of subcutaneous tumor model mouse, it is suggested that protein conformational changes occur in the tumor tissue within few minutes after euthanasia of the mouse. No more change is observed for the following ten minutes. Any alterations in the molecular level are not observed in normal skin, muscle tissues. Since the change completes in such a short time, it is suggested that this phenomenon caused by termination of blood circulation.

Development of in vivo fiber-optic Raman spectroscopy system with a miniaturized endoscope: demonstrations at the rat gastroesophageal epithelia

In vivo measurements of Raman spectra have been performed at the gastroesophageal epithelia of living rats by combining fiber-optic Raman spectroscopy system with an available endoscope unit for experimental animals. In our system, the endoscope worked well for a navigator with a probe channel, imaging and lighting fibers. Demonstrating in vivo Raman spectroscopy at the epithelia, the performance of our system was evaluated.

Development of the optical biopsy system for small experimental animals

Development of the optical biopsy system for experimental small animals is in progress. A prototype of the system which consists of a miniaturized gastro endoscope unit and Raman probes has been completed by now. The system is developed to study a gastric cancer rat model. The endoscope is 2.5 mm in diameter and is equipped an imaging bundle fiber, illumination fibers, a channel and a mechanism to angle the probe head. The head of the Raman probe comes out through the channel and it is possible to aim the probe to the target watching on the monitor. The endoscope was inserted into the anaesthetized healthy rat under the breathing support. It was successfully observed inside of the stomach of the living rat and measured Raman spectra. The spectrum of blood vessels contains the strong contribution from lipids. The present results demonstrate high potential of the system in the in vivo Raman study using the rat model.

Fabrication of microlens and microlens array using CO 2 laser and characterization of formation process

Microlenses and microlens arrays were formed directly on a surface of a glass plate by using a CO2 laser. This method has the merit of complete dry processing. We discuss about the formation mechanism and process through the characterization of the composition and refractive index distribution within the microlens.

Fabrication of microlenses and microlens arrays using local melting of glass plate by CO2 laser

Microlenses and microlens arrays were formed directly on a surface of a glass plate by use of a CO2 laser. By heating the surface of a glass plate locally to a working point of the glass material using CO2 laser beam, the surface became a hyperboloid owing to surface tension, which resulted in microlens. This method has the merit of complete dry processing. Several types of glass materials were tested. It is important to choose the type of glass with thermostable property with small expansion coefficient. It was found possible to make easily microlens and arrays with different focus lengths by controlling a laser power and a irradiated position. Typically, a CO2 laser power of 1.5W and an irradiation time of 1.1s were used to fabricate a microlens with a 170 micrometers diameter and 181 micrometers focal length with good focusing property. Microlenses fabricated using various beam profiles of CO2 laser were also discussed.

Characterization of the polarization properties of a laser output from a CO2 laser with a special intracavity mirror

A polarization property of a laser output was characterized for a CO2 laser with a mirror of anisotropic reflectivity for p and s polarization installed within the cavity. A slight difference of reflectivity of the mirror for p and s polarization is emphasized through the multiple reflection within the laser cavity, because a laser system forms a feedback system to reach a laser oscillation. By using this idea of feedback system, a laser output with a linear polarization of a large polarization ratio and with a specially polarized mode like TE01 which has a polarization vector tangential to a circle was obtained. A new type of measuring system is proposed to measure the polarization characteristics of the reflectivity of a mirror like sample set within a laser cavity through a laser output.