Diode-pumped All-solid-state Passively Q- Switched Yb:CaYAlO₄ Laser

Laser-diode-pumped all-solid-state pulse lasers have the advantages of compact structures,high efficiency,low cost,high peak pulsed laser output,narrow pulse width,high beam quality,etc..They have been widely used in nonlinear optics,spectroscopy,biomedical diagnosis,materials processing and other fields.Q-switching technology is one of the most important ways to create pulsed lasers.Existing research shows that Yb³⁺-ion doped laser materials have the advantages of having a simple energy level structure,high quantum efficiency,wide emission spectrum,being unaffected by excited state absorption,up-conversion,concentration quenching,etc..These are each very suitable for generating high power,near-infrared short-pulse laser beams.Meanwhile,since a doped Yb³⁺laser medium has an absorption wavelength matching the emission wavelength of its high-intensity InGaAs laser diode,a compact laser-diode-pumped all-solid-state laser can be constructed.In recent years,as a new type of erbium-doped gain material,Yb:CaYAlO₄ has been attracting the attention of academics and industrial professionals,its output characteristics in continuous lasers and mode-locked pulsed lasers has been studied with more frequency.It is worth nothing that,while current research on Yb:CaYAlO₄ pulsed lasers is related to mode-locked lasers with no report on passive Q-switched lasers,understanding the performance of Q-switched pulses from Yb:CaYAlO₄ crystal lasers helps further understand the optical properties of Yb:CaYAlO₄crystals.Therefore,it is necessary to research and explore the performance of passive Q-switched Yb:CaYAlO₄ crystal lasers.According on these researches,this paper proposes a scheme that uses SESAM passive Q-switched laser diodes pumped with Yb:CaYAlO₄to output a pulse,then studies output characteristics of the emitted pulse.Furthermore,the influence of the pump power on the pulse repetition rate,pulse width,single pulse energy and peak power are analyzed.By utilizing a fiber-coupled laser diode emitting at a wavelength of around 976 nm as a pump source and a Yb:CaYAlO₄ crystal with a Yb³⁺ion doping concentration of 1.5at.%and a thickness of 2 mm as the gain medium,a scheme of laser diode-pumped Yb:CaYAlO₄ for passively Q-switched pulsed lasers using a SESAM is proposed.This paper includes the following aspects:1.Explore the CW operation characteristics with transmittances of coupling output mirror.For the transmittance of the output mirror is 5.0%and the pump power is set about7.33 W,a maximum average the output power as high as 3.54 W can be achieved,the light-to-light efficiency is up to 48.29%,and the laser output continuous center wavelength is stable at about 1052.0 nm.2.This paper proposes a scheme of diode pumped Yb:CaYAlO₄ crystal based on SESAM passive Q-switched laser to obtain stable pulsed.By reasonably designing the resonant cavity,a stable passive Q-switched laser pulsed output is achieved,and a stable Q-switched laser pulse with the center wavelength about at 1048.6 nm.The output mirrors with T=0.5%,1.6%,2.5%,and 5.0%were used.When the transmittance of the output mirror was 2.5%,the threshold pump power is about 1.59 W,and the Q-switched laser is very stable.Under the pump power of 5.27 W,the narrowest pulse is 0.99?s.When the transmittance of OC was 5.0%,the maximum pulse energy of 22.17?J and the peak power of 17.21 W were achieved under the pump power was 7.33 W.The slope efficiency and light-to-light efficiency are 37.10%and 31.95%,respectively.