Research On The Fast Wavelength Tuning And Spectral Compression For CARS Laser Source

Coherent anti-Stokes Raman scattering?CARS?microscopy is a label-free biological imaging technology.There are many advantages in CARS microscopy including its non-invasive imaging,high sensitivity and three-dimensional chromatographic capability,so it has a very good application prospect in the field of life science.But traditional CARS systems made from Ti:sapphire pulse laser based on many space optical path have a huge volume and have poor stability,they are not only very expensive but also require technical staffs devoted to their constant alignment and maintenance.In order to overcome these problems,in the paper we make a research on the technology of the fast wavelength tuning of Stokes optical pulse,the spectral compression of the chipped pulse for CARS laser source.?1?The whole system of CARS laser source was designed based on the principal theory of fiber CARS.Determine the way to realize the fast wavelength electric tuning,the function of each part of the system and parameter selection were analyzed,the matters need attention during system building were discussed.?2?Fast wavelength tuning of Stokes optical pulse were researched theoretically,including the influence of the different parameters of liquid crystal on the response time during the wavelength tuning of Stokes optical pulse,the influence of the photonic crystal fiber?PCF?parameters and the incident optical pulse peak power on the wavelength tuning rang and the spectral width of the Stokes optical pulse.The result shows that when an optical pulse with peak power 2.7 kW is launched into a 2 m PCF,the detectable wavenumbers can reach 3509 cm^-1.?3?The system of fiber femtosecond CARS laser source were established,experiments with response time of Stokes'wavelength tuning were carried out,Research on the influence of the incidence optical pulse's peak power on the Stokes'optical pulse.The experiment results show that the response time of wavelength switching can reach 0.165 ms.The tuning range of the central wavelength of the first order soliton was from 807 nm to 1064 nm when dynamically controlling optical pulse peak power that launched into a 1.98 m PCF,with range from 0.108 kW to 2.517 kW,the theoretical detectable wavenumber will range from 432 cm^-1 to 3422 cm^-1.The high order soliton is appears when the length of PCF is increased to 3 m,the influence of high order soliton on the frequency shift of first order soliton is researched by experiments with a 3 m PCF.?4?The splicing loss of single mode fiber and PCF was 0.917dB,PCF and multimode fiber was 2.712dB.The spectral of pump optical pulse and Stokes optical pulse were compressing by the method of chipped pulse with a length of multimode fiber connected with a length of single mode fiber,research on the influence of fiber parameters to the spectral width,pulse width and central wavelength of output optical pulse.We can obtain a pulse with good spectral quality in a 29 spectral compression ratio,the spectral resolution can reach 4.92 cm^-1 theoretically.