Laser tissue interaction of a continuous wave 2μm, 3μm cascade oscillation fiber laser: sharp incision with controlled coagulation layer thickness

We studied coagulation layer controlled incision with newly developed continuous wave 2μm, 3μm cascade oscillation fiber laser in vitro. Since this laser device simultaneously oscillates 2μm and 3μm radiation, we could change tissue interaction by arranging power ratio of 2μm to 3μm radiation. About one watt of total irradiation power with various power ratios was focused to extracted fresh porcine myocardium or anesthetized rabbit on an automatic moving stage to obtain line incision. Macro photograph and microscopic histology were used to observe tissue interaction phenomenon. The incised specimen showed that precise cutting groove with thin coagulation layer was attained by 3μm based radiation, mean while addition of 2μm radiation to 3μm radiation made coagulation layer thicker. A heat conduction simulator using finite-element method was used to qualitatively explain obtained coagulation layer thickness. This precise incision with controllable side coagulation layer may effective to control bleeding during incision, for instance, for skin, liver, and kidney incisions. Pure continuous wave radiation of 2μm and 3μm may eliminate stress wave induced tissue damage which is frequency found in Ho:YAG and/or Er:YAG tissue interactions. Moreover, sapphire fiber might offer flexible power delivery to this new laser to establish endoscopic application and/or to improved beam handling.