Research On Output Properties Of LD Pumped All-Solid-State Passive Q-switching Tm³⁺,Ho³⁺ Laser

Laser diode （LD） pumped passive Q-switching laser provides many advantages such asminiaturization, simplification, simplify operation, high efficiency, low costing and so on, itcan be widely applied in fields as long distance accurate measuring, optical informationstorage, infrared remote sensing, clinical medical and so on.2m lasers wave band are ideallight sources for surgery, laser rangefinder, coherent Doppler radar, differential absorptionradar and so on due to that the output wave length is among eyes-safe wave band and has anexcellent transparency for atmospheric transmission. Thus, it is significant to research onoutput properties of diode end-pumped passive Q-switching Tm,Ho:YLF laser.In this paper, continuous end-pumped mode is applied, and Cr²⁺:ZnS is used as saturableabsorber for the passive Q-switching Tm,Ho:YLF laser. Photon number density distribution ofintracavity is considered under the condition of Gauss distribution. Rate equations model isbuilt based on Tm-Ho co-doped energy level structure and passive Q-switching principle.Then, starting from rate equations model, pulse form and its dynamics processes arenumerical simulated. The change law of particle number density of each energy level andsaturable absorber, inverted population density, and photon number density as a function oftime are given. And the influence and interaction relationships of inverted population density,particle number density of saturable absorber and photon number density are also given. Theirconsistency is compared in a general survey. Laser dynamic behavior for each particle numberdensity versus time is reasonably illustrated.Based on rate equations, peak power, pulse energy, pulse width, and repetition frequencywere introduced. The simulation of pump power, the gain medium length, the density ofsaturable absorber ground-state particles, the length of saturable absorber, output mirrorreflectivity, the cavity of the passive loss and the influence of cavity length on the laser outputcharacteristics was given. And then, the optimized recommendation was proposed.Subsequently, the influence of up-conversion on laser output characteristics was observed bychanging the system parameters one by one when the energy transfer up-conversion was takeninto account or not, respectively.