Investigations Of Second Harmonic Generation And Sum Frequency Generation Based On Nd:YAG Dual-wavelength Lasers

Passively Q-switched laser has advantages with compact structure,stable performance and moderate price.By using Cr,V,carbon nano-tube and black phosphorus,passively Q-switched laser at the wavelength from near-infrared to mid-infrared can be obtained.Until now,there are few researches about the passively Q-switched dual-wavelength laser,especially based on synchronization of dual-wavelength lasers.Dual-wavelength laser has many profound applications in various fields,for instance,generating terahertz laser through difference frequency generation and visible laser by second harmonic generation for color display,the medical treatment.For an effective difference frequency generation or second harmonic generation,synchronization of dual-wavelength lasers is indispensable.However,with lasers at different wavelengths,saturable absorber makes different effects,which will easily cause the out-synchronization between the dual-wavelength lasers.In this paper,the development about the second harmonic generation and the sum frequency generation of solid state multi-wavelength lasers was comprehensively investigated.And multi-wavelength passively Q-switched lasers at 1319 nm,1328 nm and 1338 nm were firstly realized with a Nd:YAG/YAG/V³⁺:YAG/YAG composite crystal.Compared to the results of system using separated Nd:YAG and V³⁺:YAG crystal,the research of system using Nd:YAG/YAG/V³⁺:YAG/YAG composite crystal shows that using composite crystal can weaken the thermal effect and improve the laser performance.Based on the system mentioned above,a LBO crystal was added into systems to generate the second harmonic generation and the sum frequency generation red lasers.Besides,the synchronization of passively Q-switched dual-wavelength lasers was investigated based on the laser performance of the second harmonic generation and the sum frequency generation.Investigation in this paper are as follows:?1?Continuous-wave dual-wavelength laser and red laser were realized by using a Nd:YAG crystal.And theirs'output performance like average output power and the spectra were investigated.?2?Passively Q-switched red laser were realized with separated Nd:YAG and V³⁺:YAG crystal and Nd:YAG/YAG/V³⁺:YAG/YAG composite crystal.We investigated the output performance of these two experiments,such as average output power,the pulse width,the pulse repetition rate and the spectra.Comparative analysis between the phenomenon in passively Q-switched system and continuous-wave system was carried out to study the synchronization of passively Q-switched dual-wavelength lasers.?3?The low sum frequency generation in the passively Q-switched system was pointed out to be caused by the mismatching dual-wavelength lasers in the passively Q-switched system.To realize the synchronization between the dual-wavelength lasers,a passively mode-locked system was proposed and proved to be valid.