<title>Investigation of mode-locked, tunable from 1350 to 1550 nm, Cr<formula><sup><roman>4+</roman></sup></formula>:Y<formula><inf><roman>3</roman></inf></formula>Al<formula><inf><roman>5</roman></inf></formula>O<formula><inf><roman>12</roman></inf></formula> laser for medical applications</title>

Abstract

We report on investigation of mode-locked regime in tunable Cr<SUP>4+</SUP>:YAG laser. Our experiments have been performed using Nd:YAG laser for pumping Cr<SUP>4+</SUP>:Y<SUB>3</SUB>Al<SUB>5</SUB>O<SUB>12</SUB> laser. We have obtained mode-locked generation of tunable radiation in the range from 1,350 to 1,550 nm. There was a generation with pulse duration in ps range and repetition rate of 320 MHz. Using a 0.5 percent transmitting output mirror, as high as 305 mW of useful output power at 1.5 micrometers was obtained from the laser with 5.5 W of absorbed pump power. The laser has threshold for mode-locked regime near 7 W for synchronous mode locking and 5 W for active mode locking. We have analyzed the laser system with Kerr lens feedback in the phase trajectory of five-dimensional space. The computer simulation have shown the presence of asymptotically stable stationary point in behavior of temporal Gaussian beam similar spatial mode structure in the resonators, when the temporal mode does not change passing through all dispersion element in laser. Our calculations show that the sign of dispersion is very important for formation of phase portrait in our laser system. In conclusion, we have demonstrated Cr<SUP>4+</SUP>:YAG laser operation in mode-locked regime on the edge of stability region. The analysis of the solutions in our model reveals that chaotic instabilities can be reached through increasing of non-linear interaction temporal and spatial Gaussian beam. The characteristics of this laser systems can provide the source of laser radiation for diagnostics and therapy.