title: Cone-shell Raman spectroscopy (CSRS) for depth-sensitive measurements in layered tissue.
abstract: We report the development of a depth-sensitive Raman spectroscopy system using the configuration of cone-shell excitation and cone detection. The system uses a 785 nm diode laser and three identical axicons for Raman excitation of the target sample in the form of a hollow conic section. The Raman scattered light from the sample, passed through the same (but solid) conic section, is collected for detection. Apart from its ability of probing larger depths (~ few mm), an important attraction of the system is that the probing depths can be varied by simply varying the separation between axicons in the excitation arm. Furthermore, no adjustment is required in the sample arm, which is a significant advantage for noncontact, depth-sensitive measurement. Evaluation of the performance of the developed setup on nonbiological phantom and biological tissue sample demonstrated its ability to recover Raman spectra of layers located at depths of ~2-3 mm beneath the surface.
authors.affiliation: Optical Spectroscopy and Diagnostic Lab, Laser Biomedical Applications and Instrumentation Division, R & D Block-A1, Raja Ramanna Centre for Advanced Technology, Indore, 452 013, India.
authors.forename: Khan Mohammad
authors.initials: KM
authors.lastname: Khan
authors.affiliation: Optical Spectroscopy and Diagnostic Lab, Laser Biomedical Applications and Instrumentation Division, R & D Block-A1, Raja Ramanna Centre for Advanced Technology, Indore, 452 013, India. shkm@rrcat.gov.in, shovan.k.majumder@gmail.com.
authors.forename: Shovan Kumar
authors.initials: SK
authors.lastname: Majumder
authors.affiliation: Optical Spectroscopy and Diagnostic Lab, Laser Biomedical Applications and Instrumentation Division, R & D Block-A1, Raja Ramanna Centre for Advanced Technology, Indore, 452 013, India.
authors.forename: Pradeep Kumar
authors.initials: PK
authors.lastname: Gupta
mesh_terms: D000082:Acetaminophen / Q000737:chemistry; D000818:Animals; D002645:Chickens; D004867:Equipment Design; D008027:Light; D018482:Muscle, Skeletal / Q000737:chemistry; D010232:Paraffin / Q000737:chemistry; D019047:Phantoms, Imaging; D019904:Polymethyl Methacrylate / Q000737:chemistry; D011137:Polystyrenes / Q000737:chemistry; D012542:Scattering, Radiation; D013059:Spectrum Analysis, Raman / Q000295:instrumentation* / Q000379:methods*; D013977:Tibia / Q000737:chemistry
chemical_list: D011137:Polystyrenes; D000082:Acetaminophen; D010232:Paraffin; D019904:Polymethyl Methacrylate
keywords: Cone-shell Raman spectroscopy (CSRS); axicon lens; depth-sensitive measurement; scale subtraction