Theoretical and experimental investigation of polarization coexistence and switching in an optical bistability Tm,Ho:LLF laser

Abstract

We first investigate the polarization coexistence and switching between the orthogonal π- and σ-polarization states in a free running optical bistability Tm,Ho:LLF laser. The output performances of the optical bistability Tm,Ho:LLF laser is numerically simulated, based on a new rate equation theory model taking into account the influences of polarization-dependent gain and losses. The simulation results show the polarization coexistence and switching of output laser in the process of decreasing pump power. The physical mechanism of polarization coexistence and switching is clarified by analyzing the polarization-dependent net-gain coefficients. Furthermore, the polarization coexistence and switching are experimentally realized in the optical bistability Tm,Ho:LLF laser, which validates the theoretical analysis. The theoretical model can be applied to analyze the polarization coexistence and switching in other kinds of (quasi-) three-level optical bistable lasers.

Watt-Level Diode-End-Pumped Self-Mode-Locked Tm,Ho:LLF Laser

“…Therefore, high-power picosecond 2 µm pulse lasers are of interest for minimally invasive surgery and better than conventional medical lasers with a pulse duration longer than nanoseconds. Typically, a solid-state laser around 2 µm is achieved using singly thulium (Tm 3+ )-or holmium (Ho 3+ )-doped and Tm 3+ , Ho 3+ co-doped bulk materials [11][12][13]. Compared with the Tm 3+ -doped laser, the Ho 3+ -doped laser features the merits of natural emission slightly above 2 µm based on the electronic transition 5 I 7 → 5 I 8 independent of the host material, which can not only avoid detrimental water vapor absorption/dispersion in the atmosphere but also realize nonlinear frequency conversion of the nonlinear crystals such as ZnGeP 2 [14] and orientation-patterned GaAs [15], which have high absorption losses at wavelengths shorter than 2 µm.…”