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Transmission characteristics of sealed hollow waveguides for Er:YAG laser radiation and their application in the ophthalmology

For the last years, several types of hollow waveguides have been under development and, as proved, these waveguides can deliver radiation to the target with high transmittances. The problem appears in the case of the so-called 'contact mode' when, in medical applications, the end of the waveguide is in contact with the soft or hard tissues. The irradiated substance is melted or ablated and a part of this material usually destroys the inner surface of the waveguide end. To overcome these problems, the end of the hollow waveguide must be sealed .In this paper, the results with two types of sealed hollow waveguides prepared for the delivery of Er:YAG laser radiation were investigated. Sealing was conducted by a cap of short Pyrex or fused silica glass tube whose inner diameter was just slightly larger than the outer diameter of the hollow waveguide to be sealed. The transmittance of the fused silica cap connected with the hollow glass waveguide was measured to be 94%, Pyrex glass cap transmittance was found to be slightly smaller (78%). The damage output energy threshold of the cap material was found 750 mJ. This value was sufficiently high for using this sealed waveguides in the ophthalmology application.