Design and realization of a fiber delivery system for the continuous wave and pulsed CO₂ laser

Recently, hollow wave guides (HWG) have become available enabling CO₂ beam delivery for treatments in less accessible parts of the human body. In this study, an IR fiber delivery system was designed which can easily be attached to and removed from an existing medical laser (Coherent Ultra-Pulse 5000C) without interference with its normal functionality. The system accepts SMA terminated HWG with an inner diameter as small as 320 μm. Measurements were performed with 320-1000 μm diameter HWG (Rutgers University, USA). The coupling losses were around 10%. Transmission losses were up to 2.5 dB/m and depended on the bending radius of the fiber. The fibers tolerated pulse energies up to 400 mJ with peak powers of 800 W and an average power of 10 W. The beam quality was preserved during transmission. Despite the losses, the output energy easily exceeded the threshold for tissue ablation. The IR fiber delivery system was successfully used in a clinical setting. The flexible 320 μm fiber was introduced through the 1 mm working channel of a 2.3 mm fiber-endoscope with a 90 degree bendable tip. Tissue was effectively ablated with pulses up to 300 mJ out of the fiber. To prevent damage due to pollution of the coating inside the HWG, it will be necessary to close the distal end of the fiber by an IR transmitting material. The IR fiber delivery system has shown to be practical in clinical use without interference with the normal functionality of the CO₂ laser. The system enables endoscopic application of CW and pulsed CO₂ laser light.