Effects of simultaneously fiber transmitted erbium and holmium radiation on the interaction with highly absorbing media

Erbium and Holmium lasers have both been shown to be suitable for orthopedic surgery performed under water. Erbium lasers emitting in the 3 micrometers wavelength region corresponding to the maximum water absorption peak effectively ablated biological tissues with high precision and minimal thermal damage. Holmium laser radiation at 2 micrometers , due to a lower absorption coefficient, is characterized by a greater extent of thermal damage leading to hemostasis. To combine the special advantages of each system we simultaneously coupled their radiation into a zirconium fluoride fiber (ZrF4) which was protected with a quartz fiber tip. Pressure measurements performed in the liquid using a piezo electrical transducer, transmission measurements and video flash lamp schlieren imaging of the laser induced vapor bubble were used in order to determine optimum laser parameters. The cutting efficiency of the Erbium laser is drastically improved when a low energy Holmium laser pulse is additionally used which is just able to open a vapor channel through which the Erbium laser pulse can be transmitted. The dynamics of the channel formation, geometry and life time are measured as a function of the delay time between the two different laser pulses and the pulse energy applied. The combination of 2 micrometers and 3 micrometers radiation seems to be an ideal instrument for tissue treatment.