Metallic hollow waveguide based on GeO₂–NaOH precursor solution for transmission of CO₂ laser radiations

By using the GeO₂–NaOH precursor solution, the hexagonal structural GeO₂ reflective films with high flatness were grown on the inner wall of stainless steel (SUS) capillary tubes by liquid phase deposition method. XRD and SEM were measured to investigate the structure and surface roughness of GeO₂ films prepared with different precursor solution. Subsequently, the transmission losses were measured and calculated which revealed the transmission loss was only one third of previous value in the sample using the glass tube. Considering the processing technology limit of 1 mm-bore hollow waveguide, the output energy distribution of the 1.5 mm-bore sample approximates to Gaussian distribution which may excite the less high-order modes. Furthermore, the full divergence angles, bending loss and output power were further investigated. These results demonstrate that the transmission performance of the GeO₂ SUS tube-based hollow waveguide can meet the requirements for laser surgery and material processing.