Wide-Field Detected Fourier Transform CARS Microscopy

Abstract

We present a wide-field imaging implementation of Fourier transform coherent anti-Stokes Raman scattering (wide-field detected FT-CARS) microscopy capable of acquiring high-contrast label-free but chemically specific images over the full vibrational ‘fingerprint’ region, suitable for a large field of view. Rapid resonant mechanical scanning of the illumination beam coupled with highly sensitive, camera-based detection of the CARS signal allows for fast and direct hyperspectral wide-field image acquisition, while minimizing sample damage. Intrinsic to FT-CARS microscopy, the ability to control the range of time-delays between pump and probe pulses allows for fine tuning of spectral resolution, bandwidth and imaging speed while maintaining full duty cycle. We outline the basic principles of wide-field detected FT-CARS microscopy and demonstrate how it can be used as a sensitive optical probe for chemically specific Raman imaging.

High‐speed broadband Fourier‐transform coherent anti‐stokes Raman scattering spectral microscopy

“…In this Letter, we demonstrate broadband FT‐CARS spectral microscopy with a pixel dwell time of 42 μs, which is a record pixel dwell time and ~50 times shorter than the pixel dwell time previously reported for CARS spectral microscopy . Our broadband FT‐CARS spectral microscope is composed of a rapid‐scan FT‐CARS spectrometer, a rapid galvanometric scanner, and a high‐speed image acquisition circuit, enabling a frame rate of 2.4 fps with a pixel resolution of 100 × 100 pixels, a broad bandwidth of 600–1200 cm −1 , a theoretical spatial resolution of 0.95 μm, which is estimated by the diffraction limit, and a spectral resolution of 17 cm −1 (without a window function) or 37 cm −1 (with a Hanning window function).…”

Broadband Coherent Raman Scattering Microscopy

“…Recently, this system has been equipped with a higher‐frequency galvo mirror (50 kHz), which allows the measurement of 50 000 spectra per second . Finally, Duarte et al . recently extended FT‐CARS to wide field detection, using galvanometric mirrors for rapid scanning of the focal plane combined to an electron multiplied CCD camera for sensitive acquisition of the CARS signal.…”

Raman Imaging Spectroscopy: History, Fundamentals and Current Scenario of the Technique

“…Table S5 (in the SI section) presents a summary of some applications found in this area. Duarte et al, 79 for example, developed CARS microscope with Fourier transform for imaging. Using this equipment, it was possible to obtain an image of the entire region at the same time, decreasing the damage to the sample.…”

“…Using this equipment, it was possible to obtain an image of the entire region at the same time, decreasing the damage to the sample. 79 Modifications in the TERS tips are also found, aiming at improving the performance of the method, 80,81 the techniques to improve data (e.g., removal of spikes or improving signal to noise ratio), 82,83 the development of SORS for linear mapping, 84 and others. It is possible to find articles that try to develop new equipment or do modifications for new applications and/or performance improvements, as well as new modes of data processing.…”