Study On Cascaded Stimulated Raman Scattering Of Carbon Tetrachloride

Carbon tetrachloride is an excellent organic solvent.It can also be used in physics,chemistry,medicine and other fields as chlorinating agent of organic substances and extractant of drugs;It is also widely used in production and life as a solvent for spices,a degreaser for fibers,a cooking agent for grains,and a drycleaning agent for fabrics.It has stable chemical properties at room temperature.It is a kind of volatile colorless transparent liquid,which is harmful to human body.In1987,the United Nations adopted the Montreal Protocol on substances that Deplete the ozone layer and its amendment to strictly limit the emission of carbon tetrachloride to protect ozone layer substances.The research on the properties and structures of carbon tetrachloride plays a very important role in the fields of physics,chemistry,biology and medicine,and has always been a hot topic for researchers.Raman spectroscopy can analyze the structure of substances and measure the content of substances.After the 1960 s,with the invention of lasers and the support of weak signal detection technology,Pullman spectroscopy has made great progress in many fields.By measuring Raman spectroscopy,we can observe the characteristic peak position of substances,analyze their structure and properties,and understand the intrinsic vibration mode of substances.In this paper,the cascaded stimulated Raman scattering spectra,excitation threshold,Kerr self-focusing and other nonlinear optical processes of carbon tetrachloride are studied.(1)The Stimulated Raman Scattering(SRS)process of carbon tetrachloride was studied using a nanosecond 532 nm pulsed Nd: YAG laser.The pump laser passes through a 10 cm sample cell,and the output light includes Stokes light,anti-Stokes light and transmitted pump beam.The first-order,second-order,third-order and fourth-order Stokes and anti-Stokes stimulated Raman scattering of carbon tetrachloride symmetric stretching vibration modes are obtained.When the pump laser passes through the 20 cm sample cell,with the increase of the pump energy,the fifth-order Stokes stimulated Raman scattering is observed for the first time at the pump energy of 3.496 m J.Kerr Self-focusing leads to filament phenomenon,which reduces the SRS threshold and improves the SRS strength of different vibration modes.(2)The Cascaded Stimulated Raman Scattering effect is obtained by using a double sample cell.After the pump laser passes through the first sample cell(C1),the output light includes the transmitted pump light and Stokes SRS light.The frequency difference between them matches the symmetrical stretching vibration frequency of C-Cl,which realizes the resonance enhancement of SRS signal in the second sample cell(C2).The first-order,second-order,third-order and fourth-order Stokes and antiStoke stimulated Raman scattering of C-Cl symmetric stretching vibration modes are obtained;With the increase of the pump energy,the fifth-order Stokes stimulated Raman scattering is obtained at the pump energy of 3.235 m J.At this time,the pump energy is less than 20 cm single sample cell.This method not only reduces the threshold of stimulated Raman scattering,but also improves the SRS intensity of different vibration modes.The energy conversion efficiency can reach 51%.