Research About Stimulated Raman Scattering In Liquid Fiber

For many years laser Raman spectroscopy has been an importanttool for the investigation of microscopic molecular structure. Its intensity,frequency shift, line width, characteristic peaks and so on have closerelation with molecule's vibration, rotation, symmetry property and otherelse information of fine-structure. But Spontaneous Raman Spectroscopy isa kind of weak spectroscopy, and a representative data of scattering sectionis below 10 ?30cm .Of course ,along with invention of laser ,Raman 2Spectroscopy be used in many fields .Raman Spectroscopy is still so weakthat we need special instrument to get Raman Spectroscopy and only littlenoise of light could shield correct Raman Spectroscopy .All of these haverestricted applications in many fields. Discover of Stimulated Raman Scattering (SRS)that hascharacteristic of high reciprocal coefficient ,strong signal , high transitionefficiency etc. ,let Raman Spectroscopy be used in a wider field .SRS isnon-linear optic phenomena ,and it be discovered by E.J.Woodbury andW.K.Ng at 1962.Since discover of SRS ,we utilize its wide range ofspectroscopy , high transition efficiency and homochromy to apply it in thefield of information technology ,optics communication , spectrumtechnology ,laser technology , sensor and otherwise. Liquid-core optical fiber(LCOF) is a new type component ofoptic ,and it be consisted of liquid core , envelope (quartzose ,glass orpolymer) ,and a safe-layer .LCOF has a bigger diameter and IA than solidfiber , and LCOF have some characteristics include wide range of spectrumtransmission ,high transmission efficiency and long used life .Toabsorption light ,longer length of absorption pool ,more delicacy fromLombard-Bill law .LCOF have been used for Raman Spectroscopy since itinvented .To scattering spectroscopy , intensity of spectrum will enhancewith that laser transmit in fiber .Because a fiber could be very long ,soRaman spectrum be "magnified" in fiber . Threshold value of SRS can be 102~103 lower if applying thetechnique of liquid core optics fiber (LCOF) together with stimulatedRaman effect . This is a new experiment technique .Through application ofLCOF ,we can get SRS spectrum at low laser power, and avoid the choiceof Raman matter that could bring SRS .So we can use SRS as a tool in thefield of matter analysis and biology molecule detect ,the strongpoint ofSRS could be exerted . 第 58 页吉林大学硕士学位毕业论文 The fiber used in my experiment is made of high quality quartz ,andits two side is enveloped with quartz coupling- component. Thespectrophotometer is a Dilor－Omars 89 made in France .In this paper ,sample that we used include a pure solvent(CS2) and 10-6～10-8 mol lβ-carotene in CS2, we get the SRS spectrum under different laser power . Through experiment data, we prove that threshold value of SRScould be reduced in LCOF. Analyses the data ,we detect that the thresholdvalue and the max peak value of SRS will change when the concentrationof β-carotene is different . Rule is :to 1st stokes SRS spectrum, thresholdvalue will reduce if the concentration of β-carotene in CS2 decrease, butthe relation is not linearity; the max peak value will increase whenconcentration decrease. Reason of this phenomenon is when Stokes line isin the fluorescence range of another matter, and the wavelength of laser isin the absorption range of this fluorescence matter. Then the Stokes line beenhanced and other Stokes lines out of the fluorescence range areweakened. In the experiment, we find that wasting in optical fiber is largeralong with longer fiber. So, there is a point that the enhance and ullagecould be balance, The value of this point, called the optimum length or theshortest length, can be computed by a formulae, which can give off aconclusion L = 2αF, namely the value of the sho...