Spectral interferometric polarization-CARS for hyperspectral imaging

Abstract

The third-order nonlinear nature of Broadband CARS means it has the inherent capability to produce label-free images using vibrational information as contrast. The speed of the technique is several orders of magnitude greater than spontaneous Raman spectroscopy. This has implications for enabling diagnostics in areas such as histology, immunology and cytology. The major drawback in BCARS currently preventing these applications is mainly the nonresonant background, present due to degenerate four-wave mixing. This background can be removed using the tensorial properties of the electronic susceptibility. This technique is known as spectral interferometric polarization CARS (SIP-CARS). We show an implementation of SIP-CARS on highly resonant polymer beads for spectroscopic imaging using two sequential BCARS scans to probe different components of the susceptibility tensor.