Study On Metallic Capillary Tube Based GeO₂ Attenuated Total Reflection Mid-infrared Hollow Waveguide

Mid-Infrared?mid-IR?laser,such as CO₂ laser,is a series of lasers located at the atmospheric window of 8-14?m wavelength.It is important in military and domestic applications such as infrared radar,infrared imaging,chemical sensor,electron transport manipulations of narrow gap semiconductors,laser surgery and material processing.Attenuated total reflection?ATR?hollow waveguides for delivery of CO₂ laser has advantages like simple structure,no end-reflection,good transmission modes,high thermal damage threshold and small output beam divergence.This kind of hollow waveguide has been a heated topic in the field for a long time.Glass capillary tube based GeO₂ ATR hollow fibers have problems such as brittle and low heat conductivity.To solve such problems,our group proposed the idea to prepare metallic capillary tube GeO₂ ATR hollow waveguide with LPD method.Stainless steel?SUS?is well studied and widely used in industrial applications.The fabrication of SUS capillary tube GeO₂ ATR hollow with low cost LPD process has been studied for the first time.An extensive study on the influence of LPD cycles on the transmission characters is also carried out based on SUS ATR hollow waveguide.Thermal oxidation may occur when metallic capillary tube based GeO₂ ATR hollow waveguides are used to transmit high power laser beams.This may do irreversible damage to the waveguide.Ni-Cr is an alloy known for high temperature resistance and oxidation resistance.In this work,Ni-Cr capillary tube is examined as a category of structural tube for establishing a metallic?ATR?GeO₂ hollow waveguide.The fabrication,transmission characters and its ability to resist high-temperature thermal oxidation are studied.The temperature rise of the operating waveguide may affect the laser delivery stability and the laser surgery safety.The thermal behaviors of the metallic ATR hollow fiber transmitting CO₂ laser were investigated theoretically and experimentally in this work.The influence of input laser power on fiber temperature has been quantitatively discussed.In applications such as laser surgery and material processing,maximum input laser powers for SUS-based and Ni-Cr-based ATR hollow waveguides are evaluated based on the theoretical and experimental results.This work offers theoretical and technical supports for hollow waveguide delivery of CO₂ laser radiations.