Investigation Of The Continuously Tunable Single-frequency Laser

All-solid-state single-frequency continuous wave?CW?lasers have been essential light sources for many fields of scientific researches and applications,such as quantum precision measurement,cold atomic physics,quantum optics,quantum information,high-resolution spectroscopy,and so on,owing to their merits of high coherence,low intensity noise,high beam quality and narrow linewidth.With the tremendous progress of the scientific research,the single-frequency laser with higher output power and higher stability are desired in the fields of quantum information and precision measurement.Simultaneously,they also required the lasers can maintain stable single-longitudinal-mode state under long term operation.In addition,the stable single-frequency lasers with continuous frequency tuning are required in fields of cold atomic physics and laser radar.So,the realization of continuous frequency-tuning of the all-solid-state single-frequency CW lasers and the enhancement of long-term stability of the all-solid-state single-frequency CW lasers have been investigated deeply in this thesis.The specific contents of research are listed as following:1.The continuous frequency-tuning of laser was implemented by utilizing electro-optic effect to lock etalon and an all-solid-state single-frequency CW Ti:sapphire laser with broad tuning range was developed.We firstly designed the control program of coarse tuner birefringent filters in laser resonator based on the LabVIEW and realized the automatical and broad tuning of the laser by feedback controlling the angle of the birefringent filters.On this basis,the continuous frequency-tuning of the laser was implemented by locking the intracavity electro-optic etalon and continuously scanning the length of the laser resonator.Owing to the electro-optic effect of the optical crystal was used to modulate the intracavity laser intensity for the etalon locking,the frequency of the modulation signal can be selected arbitrarily without any restriction.By changing the frequency of the modulation signal,the intensity noise of the laser was successfully manipulated.In experiment,the automacical and broad tuning range of the all-solid-state CW single-frequency Ti:sapphire laser was110 nm?760 nm-870 nm?and its continuous frequency-tuning range was 20GHz.2.The continuous tuning range of a CW single-frequency laser was expanded by combining an intracavity locked etalon with a nonlinear loss,which broke through the restriction of free spectrum range of the etalon on the maximal continuous frequency-tuning range of the laser.By using this method,a CW single-frequency intracavity frequency-doubled Nd:YVO₄/LBO laser with continuous frequency tuning range of 222.4 GHz at 532 nm was obtained,which is,to our best knowledge,the available CW single-frequency laser with the broadest continuous tuning range.By using that method,we also attained a continuously tunable intracavity frequency-doubled Nd:YAP/LBO laser with1080 nm/540 nm dual-wavelength output.The obtained mode-hoping free tuning range was 146.7 GHz at 540 nm and the output power of the laser at540 nm and 1080 nm were 4.18 W and 2.39 W,respectively.Owing to the obtained laser can be continuously tuned in a wideband range,it could maintain stable single-longitudinal-mode state under long-term operation,without any multi-mode oscillating and mode-hopping phenomenon.3.We proposed a method to enhance the stability of the laser output via feedback control to nonlinear loss in the laser resonator and the stability of a single-frequency fundamental wave 1064 nm laser was effectively improved.In experiment,the LBO crystal was inserted into the laser resonator to introduce the nonlinear loss,and the nonlinear loss could be manipulated by controlling the temperature of the nonlinear crystal,then the output power of the laser was changed.With the feedback control loop,the fluctuation of the laser output power was reduced from±0.59%to±0.26%within 2 hours.Simultaneously,the frequency drift of the laser was also reduced from 21.82MHz to 9.84 MHz.The experimental results showed that,by feedback controlling the nonlinear loss,not only the power stability but also the frequency stability of the single-frequency CW laser was significantly improved.Innovative works:A.Realizing the continuous frequency-tuning of laser by utilizing electro-optic effect to lock etalon and developing an all-solid-state single-frequency CW Ti:sapphire laser with broad tuning range and intensity noise manipulation;B.Expanding the continuous tuning range of a single-frequency CW laser by combining an intracavity locked etalon with a nonlinear loss,and obtaining an all-solid-state single-frequency CW Nd:YVO₄/LBO laser and an all-solid-state single-frequency CW Nd:YAP/LBO laser with continuous frequency tuning;C.Enhancing the stability of all-solid-state single-frequency CW laser via feedback control to the nonlinear loss in the laser resonator.