Determination of the confocal volume of a Raman microscope for probing for single-molecule SERS applications

Abstract

The confocal volume in Raman spectroscopy refers to the sample region from which scattered photons are collected by a confocal Raman spectrometer, defined by the cone-shaped light beam generated by the microscope’s objective lens in the confocal configuration. The confocal volume is characterized by the confocal height and confocal area, which determine the range of heights and lateral positions, respectively, from which the spectrometer effectively collects scattered photons. In the present study, the confocal height and area were calculated for different configurations of a confocal Raman spectrometer to obtain the confocal volume using a Si wafer sample. Understanding the confocal volume was essential to optimize Raman microscopy experiments and estimate the number of molecules generating surface-enhanced Raman scattering spectroscopy spectra in a single-molecule regime.