Mitsunori Saito

Infrared image guide with bundled As–S glass fibers

An infrared image guide made of bundled As-S glass fiber cores has been developed. The transmission range of this fiber was 2-6 microm. At the 3.3- and 4.8-microm wavelengths the minimum optical loss was 0.6 dB/m. With this image guide efficient transmission of the thermal image was experimentally established.

KRS-5 optical fibers capable of transmitting high-power CO 2 laser beam

Polycrystalline KRS-5 optical fibers were experimentally demonstrated to have high-power transmission capabilities for a cw CO(2) laser beam. A typical sample of fibers provided by extrusion, 1 mm in diameter and 0.87 m in length, carried a laser power of 68 W to its output end and was found to remain free from damage at an incoming laser intensity up to 30 kW/cm(2).

Temperature dependence of the Faraday effect in As–S glass fiber

Temperature dependence of the Faraday effect is investigated for As2S3 fiber at 3.39 microm, obtaining a Verdet constant V of 1.62 x 10(-2) min/cm x G at room temperature and a temperature-dependence term coefficient of 10.67 min x K/cm x G in the experiments. The V value obtained at 25 degrees C is consistent with the theoretical estimates based on the first derivative of known refractive indices with respect to the wavelength. The temperature-dependent term is also discussed theoretically.

Teflon‐clad As‐S glass infrared fiber with low‐absorption loss

An As‐S glass fiber with Teflon Fluorinated Ethylene Propylene (FEP) cladding has been fabricated. The transmission range of this fiber was 1–7 μm with two pronounced absorption peaks at 2.8 and 4.1 μm. It was found that these absorptions were caused by moisture adsorbed on the surface of the As‐S glass as well as the hydrogen impurity due to the silica ampule. By removing these impurities the absorption loss was reduced and a minimum optical loss of 0.15 dB/m was obtained for this infrared fiber.

Power transmission capacity of As‐S glass fiber on CO laser delivery

In this paper we describe the performance of CO laser power delivery over an As‐S glass fiber, which has a fluorinated ethylene propylene resin (Teflon FEP) cladding, as well as kinetics of melting break off of the fiber on power delivery. The maximum fiber power output of 15.3 W with an intensity of 12.2 kW/cm2 was obtained by using a fiber whose core diameter was 400 μm and which was not forced cooled. Maximum transmission power was restricted by the thermal damage occurring at the end of the fiber. Kinetics of this thermal damage were investigated by measuring the temperature on the cladding surface and by estimating temperature distribution in the fiber through calculations. The localized heat input at the end of the fiber was estimated at approximately ten times higher than other portions of the fiber.

Optical remote sensing system for hydrocarbon gases using infrared fibers

An infrared optical fiber made of As2S3 glass has been applied for remote sensing of hydrocarbon gases. The fiber has enabled a transmission of the radiation at 3.39‐μm wavelength, where hydrocarbon molecules have strong absorption bands. Using a 3.39‐μm He‐Ne laser as a light source, an effective remote sensing system has been established. A detection limit of the gas concentration is ∼300 ppm for CH4 gas, which is ∼0.6% of the lower explosion limit. The system is also expected as a pressure monitor since it is highly sensitive to the gas pressure.

High power, high intensity CO infrared laser transmission through As2S3 glass fibers

Optical power transmission of 5‐μm band CO laser beam through As2S3 glass core Teflon fluorinated ethylene propylene clad fibers is described. The maximum transmitted power is as high as 62 W with a 700‐μm core diameter fiber, which corresponds to a power intensity of 16 kW/cm2 at the fiber output end. The influence of fiber bending on the transmission characteristics is also reported.

CO Laser Power Delivery By As 2 S 3 IR Glass Fiber With Teflon Cladding

The high-intensity power delivery of CO laser with a As2S3 chalcogenide glass fiber for medical applications is described in this paper. The As2S3 glass fiber which had fluorinated ethylene propylene (Teflon FEP) cladding was used in this study. The fiber output of 1 5.3W was attained by means of the fiber which had 400μm core diameter without any degradation on the fiber. At the above condition, the light intensity of 16.9kW/cm2 was obtained on the input end of the fiber. The maximum delivery power was restricted to melting of the core material at output end of the fiber. The allowable bending radius of the fiber was less than 30 mm. The applicability of this power delivery for medical applications, especially for the laser endoscopy and the laser angioplasty are discussed.

Magnetooptic-Effect Analysis of Optical Fibers Using Intracavity Scheme: Application to KRS-5 in IR Regions

A method of magnetooptic effect analysis using an intracavity method is proposed. The method is particularly suitable for optical fibers. If the lineshape parameters are known for a given laser, the Faraday and Voigt effects can be conveniently evaluated by analyzing the magnetooptically-induced intensity-variation of the oscillation output. The method has been successfully examined in KRS-5 fiber and crystal using He-Ne 3.39 µm and CO2 lasers, and the experimental results agree well with the theoretical estimates. This paper also describes a method of determining the lineshape parameters if they are not known for a particular laser.

Simultaneous delivery of neodymium: yttrium aluminum garnet and CO laser beams by a single As-S glass fiber

The simultaneous energy delivery of neodymium:yttrium aluminum garnet (Nd:YAG) and CO laser beams by a single As‐S glass fiber is described. The transmission loss in the fiber of a Nd:YAG laser beam was 2.6 dB/m under the energy delivery. A fiber output of 14 W was obtained at an approximately 1:1 power ratio from these lasers with a 400‐μm core diameter fiber.