Design Of Optical System For Tip Enhanced Raman Spectrometer

With the rapid development of nanotechnology and the increasing requirement of spatial resolution for characterization methods,various nanoscale characterization and manipulation technologies have attracted wide attention.In 2000,a Tip Enhanced Raman Spectroscopy was proposed.The Tip Enhanced Raman Spectroscopy is a surface analysis technique that utilizes near-field optical enhancement effects.It combines a Scanning Probe Microscope with Plasmon Enhanced Raman Spectroscopy to enhance Raman spectroscopy using localized electromagnetic fields near nanometer metal tip to characterize the material surface in situ,which can provide both the topographical information of the surface of the material and the Raman spectrum of the corresponding position,with spatial resolution of up to several nanometers and high-sensitivity to single molecule detection limits.TERS technology does not require special sample preparation.In theory,its spatial resolution is limited only by the size and shape of the scanning probe,and it also has extremely high detection sensitivity,which makes it a huge potential in the field of surface analysis.And it has been widely studied and applied in surface science,biology,semi-conductor and nanoscience.However,since the beginning of this thesis,only a few companies in the world can provide commercial TERS solutions,and most of them are bulky,complicated in operation and costly,which makes the application of TERS technology popular extremely limited Therefore,the development of an integrated small TERS instrument is of great significance for the promotion of the application of TERS technology and and the development of nano-scale spectroscopy in China.TERS has received increasing attention due to its ability to provide nanoscale spatial resolution and single molecule detection sensitivity for molecular fingerprinting.In this paper,an integrated optical system with high sensitivity is designed,which can be coupled with various types of SPM.The optical system directly couples the excitation and collection optical path with Raman spectroscopic splitting optical path in free space through a 45 degree edge filter,which reduces the loss of optical signal and improves the sensitivity of optical detection;The movable film spectroscope combines white illumination and microscopic imaging into the optical system,greatly simplifying the complexity of the optical system;The specially designed white uniform illumination path improves the imaging quality of the microscopic system;Spectral resolution and sensitivity are improved by adjustable slit and Czerny-Turner spectroscopic structure designed by coma elimination and spherical aberration elimination.The entire optical system has a small size of 380×180×70mm3 and its overall weight is less than 3kg.It has the characteristics of high sensitivity,high resolution and portability.The relationship between incident angle and field enhancement of polarized laser is simulated and analyzed by three-dimensional finite-difference time-domain method.The optical system developed in this paper is coupled with commercial STM at 60 degrees.The enhanced TERS signal of 4-PBT molecule is measured.The signal intensity and resolution meet the application requirements.