Investigation Of The High Quality Single-frequency Continuous-wave Ti:S Laser And Its Frequency-doubling Laser

All-solid-state single-frequency continuous wave(CW)Ti:sapphire(Ti:S)laser has been widely applied in many scientific researches,military and national defense fields including cold atomic physics,quantum optics,quantum information,precision measurement and so on owing to its intrinsic advantages of narrow linewidth,low intensity noise,perfect beam quality and high stability.However,the traditional all-solid-state single-frequency CW Ti:S laser is huge in size and complicated to operate,which seriously restricts its further applications in practice.In order to satisfy the rapid development of scientific research,the attention of our research is focused on the high quality all-solid-state CW single-frequency tunable Ti:S laser.Therefore,the specific research contents of my thesis are as follows:1.We developed an off-axis birefringent filter(BRF)to realize the wideband tuning range which could directly cover the whole fluorescence spectral range of gain crystal.With the assistance of the designed BRF,the wavelength tuning range of 304.07 nm in Ti:S laser was realized.According to the tuning theory of the off-axis BRF principle,the quantitative relationship between the optical axis diving angle and the sidebands rejection ability was deduced,and the optimal diving angle condition of a multi-plate BRF used in a single-frequency CW tunable laser was achieved.Then,a BRF corresponding to the fluorescence spectral range of Ti:S crystal(700-1000 nm)was designed according to our proposed optimal condition.The optical axis diving angle and the thickness ratio of the designed BRF were 29.1°and 1:2:5:9,respectively,and the thickness of the thinnest plate was 0.5 mm.As a result,an all-solid-state single-frequency CW Ti:S laser with the tuning range of 304.07 nm was realized by the designed BRF.2.We first implemented an all-solid-state single-frequency CW self-tuning Ti:S laser with the assistance of the birefringent characteristics of the Ti:S crystal.The crystal was designed as multi-plate self-tuning crystal(STC)with the thickness ratio of 1:2:4.It served as the gain medium as well as the frequency selector,and replaced the traditional BRF.When the designed multi-plate Ti:S crystal was inserted into the resonator,the wavelength tuning range of 108.32 nm was realized by precisely controlling the rotation of the STC in experiment.Compared to the traditional Ti:S laser,the advantages of the attained new Watt-level single-frequency CW self-tuning Ti:S laser were compact structure,high conversion efficiency and low intensity noise.3.The wavelength of the all-solid-state single-frequency CW Ti:S laser was successfully extended to 397.5 nm by Mg O:PPSLT crystal with excellent characteristics,and the obtained 397.5 nm laser could be operated steadily for long term.We employed the Mg O:PPSLT crystal to realize the freuqnecy-doubling in the experiment because of its intrinsic properties of high damage threshold,high thermal conductivity and wide transmission spectral range.After optimizing the beam waist in the center of Mg O:PPSLT crystal by designing the cavity structure,the maximal conversion efficiency was up to25.2%.The obtained maximal output power of single-frequency 397.5 nm laser was 407 m W with the pump power of 1.92 W.The M~2 values of the output laser beam were better than 1.02,and the frequency drift in 10 s was 573 k Hz.4.A method for measurement of the equivalent thermal lens focal length of frequency doubling crystal by spectrum broadening technology was proposed.In the process of the single-frequency 397.5nm UV laser generation,it was found that the obvious spectral broadening was observed with the increasing of the pump power.Moreover,the broadening degree was significantly different when the cavity length were lengthened and shortened,which showed obvious bi-stability-like phenomenon.Then,the quantitative relationship between the thermal lens focal length and the transmission peak broadening of the frequency-doubling cavity was established,and the equivalent thermal lens focal length of Mg O:PPSLT crystal under different pump power was measured.On this basis,the thermal characteristics of the frequency doubling crystal was investigated.It was shown that the thermal effect of Mg O:PPSLT crystal was mainly caused by blue-induced infrared absorption.Innovative works:A.A method for the design of the off-axis BRF covered the whole fluorescence spectral range of gain crystal was developed,and then the wavelength tuning range of 304.07 nm in Ti:S laser was realized.B.An all-solid-state single-frequency CW self-tuning Ti:S laser was developed according to the birefringent characteristics of the Ti:S crystal.C.An all-solid-state single-frequency CW 397.5 nm UV laser with long life-time was successfully realized by utilizing the Mg O:PPSLT crystal with excellent characteristics as frequency doubling crystal.D.A method for measurement of the equivalent thermal lens focal length of frequency doubling crystal by spectral broaden technology was proposed.The thermal characteristics of the frequency doubling crystal was investigated by establishing the quantitative relationship between the thermal lens focal length and the transmission peak broaden of the frequency-doubling cavity was established.