Universal Modeling Method and Simulation Study of Ho:YLF Multi-Level Optical Refrigeration System

晓明 高

Saeid Rostami, Alexander R. Albrecht, Azzurra Volpi +1 more

We report the first demonstration of solid-state optical refrigeration of a Ho-doped material. A 1 mol% Ho-doped Yttrium Lithium Fluoride (YLF) crystal is cooled by mid-IR laser radiation, and its external quantum efficiency and parasitic background absorption are evaluated. Using detailed temperature-dependent spectroscopic analysis the minimum achievable temperature of a 1% Ho:YLF sample is estimated. Owing to its narrower ground- and excited-state manifolds, larger absorption cross-section, and coincidence of optimum cooling wavelength of 2070 nm with commercially available high-power and highly efficient Tm-fiber lasers, Ho^3+-doped crystals are superior to Tm^3+-doped systems for mid-IR optical refrigeration. With further improvement in material purity and increased doping concentration, they offer great potential towards enhancing the cooling efficiency nearly two-fold over the best current Yb:YLF systems, achieving lower temperatures as well as for realization of eye-safe mid-IR high-power radiation balanced lasers.

Xinlu Zhang, Bo Jiang, Guang-Zong Dong +3 more

The optical bistability of Tm, Ho:YLF laser is theoretically investigated based on the rate equation theory model in this paper. The optical bistability output is obtained by numerical simulation, and the influence of energy transfer upconversion on the bistability behavior is analyzed. Furthermore, the formation scheme of optical bistability is also discussed by the relation between the gain and the loss. The theoretical analysis shows that the saturation of ground state reabsorption and energy transfer upconversion effect are necessary to the optical bistability of Tm, Ho:YLF laser.

A. Rayner, N. R. Heckenberg, Halina H. Rubinsztein-Dunlop

A. P. Khapalyuk

Xinlu Zhang, Bo Jiang, Guang-Zong Dong +2 more

A self-saturated absorption regime is proposed to theoretically investigate the optical bistability of Tm,Ho:YLF laser. Based on this bistability regime, the rate equation model of the optical bistability is established. The optical bistability behaviors of Tm,Ho:YLF laser are obtained by numerical simulating. The relation between laser gain and loss are also analyzed to confirm the rationality of the bistability mechanism. Furthermore, the time characters of the optical bistability are investigated. It is found that the high pulse power and the duration of the pre-pump are two major factors that affect the laser turn-on delay time and their influences on the turn-on delay are analyzed.