One-laser interferometric broadband coherent anti-Stokes Raman scattering

Abstract

Abstract:We introduce an interferometric technique for eliminating the non-resonant background of broadband coherent anti-Stokes Raman scattering (CARS) microscopy. CARS microscopy has been used for imaging a number of biological samples and processes, but the studies are mostly limited to detecting lipids in biological systems by probing the C-H stretch. Non-resonant background and incoherent noise sources can easily overwhelm less intense signals from other molecular vibrations. In this study, we demonstrate a one-laser broadband interferometric technique that separates the spontaneous Raman scattering-related component of the CARS signal from the non-resonant background using liquid benzonitrile as a model system.Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.

Picosecond spectral coherent anti-Stokes Raman scattering imaging with principal component analysis of meibomian glands

“…Broadband CARS schemes address this issue by recording a much wider segment of the Raman spectrum. In the broadband approach, the desired spectral information is attained by either resolving the broadband anti-Stokes signal on a CCD-based spectrometer [12][13][14][15] or by Fourier transforming the time-resolved anti-Stokes response. 16,17 The CARS signal yield is typically high enough to record CARS spectra over several hundreds of wave numbers with acquisition times that can be two orders of magnitude faster than what can be achieved with a spontaneous Raman microspectrometer.…”

Comparison of coherent and spontaneous Raman microspectroscopies for noninvasive detection of single bacterial endospores

“…CARS spectroscopy has provided a useful spectroscopic technique for the past 40 years, despite inherent difficulties as discussed below. However, recent years have witnessed renaissance of interest in CARS spectroscopy (5)(6)(7)(8)(9)(10)(11)(12)(13). This recent progress is driven mostly by technical developments in lasers, optics, electronics and computers, which facilitate the widespread use of this promising spectroscopic tool.…”

“…We have recently developed a simple ''one-laser'' approach to CARS microspectroscopy, which uses a single-picosecond laser oscillator to generate a broadband continuum that is then mixed with the fundamental beam to generate a full CARS spectrum (15). The large number of already existing Ti:sapphire lasers facilitates the widespread implementation of this method (11,12,17).…”

“…Heterodyne (18) and polarization-sensitive detection schemes (19), and time-delayed methods (20), have been refined to a high degree of sophistication (8)(9)(10)(11); however, most of those studies were limited to the characterization of molecular systems, which possess relatively simple vibrational spectrum and have rather large Raman cross-sections. In many recent applications, the retrieval of Raman spectrum required an additional scanning of the time delay between pump pulses, which extends the acquisition time and diminishes the advantages of CARS spectroscopy as the way for instant access to the molecular ''fingerprint'' spectral information.…”

Coherent anti‐Stokes Raman Scattering Microscopy

“…This local oscillator field represents a purely nonresonant CARS signal and can be obtained either separately from a nonresonant sample [69] or from the excitation beam itself; [70] it can also be approximated by the response of the sample to broad-bandwidth-excitation pulses. [71] Various approaches have been demonstrated both in the spectral [69,[71][72][73] and temporal [74][75][76] domain. It has been shown that a time-gated interferometric detection of the CARS signal can be used to realize chemical specificity in optical coherence tomography (OCT) measurements.…”