CARS > SOL

Advantages of CARS method

• high sensitivity: CARS generates more intensive and directed signals in comparison to spontaneous Raman microscopy;
• anti-Stokes CARS signal has frequency exceeding pumping waves frequencies and is detected in a spectral range free from the stray light of Stokes luminescence;
• CARS signal is registrated only in a focus where excitation intensity is the highest. It allows imaging with a high spatial resolution using non-confocal pinholes and also performs 3D layer-by-layer scanning with minimal neighboring layers influence on measuring results;
• spectral resolution of CARS signal is defined only by the width of pumping lasers lines, what simplifies spectral measurements, as detection of CARS signals can be performed without any spectral instrument;
• CARS signal is proportional to the squared molecule concentration, it allows using CARS (along with the selectivity and noninvasivity of the method) for quantitative measurements of chemical substance concentration in a sample;
• minimal invasive (nondestructive) CARS method for biological samples. Due to the high sensitivity of CARS method molecules in living cells can be detected without fluorescent markers.

Features

High spatial resolution:

Wide spectral range:

High spectral resolution:

Simultaneous / multifunctional analysis:

• high-speed imaging by CARS signal (no preliminary additions to the samples)
• confocal Raman imaging
• confocal fluorescence imaging including two-photon (or multi-photon) emission
• confocal imaging in the reflected laser radiation
• high-contrast imaging in the transmitted laser radiation
• visualization of a surface profile by means of the second harmonics generation signal

Three types of CARS measurements:

• F-CARS
• Е-CARS
• P-CARS

Five independent speed channels for simultaneous detection up to four 2D and 3D images:

• F-CARS: CARS signal in forward direction
• E-CARS & Raman: CARS signal in backward (EPI) direction/ Raman signal
• Reflected: reflected laser radiation signal
• Transmitted: transmitted laser radiation signal
• Luminescent: transmitted laser radiation signal
• Polarization control over the excitation and detection
• Mono-block laser system for CARS signal excitation
• Additional laser 633nm for excitation of a conventional one-photon fluorescence and spontaneous Raman scattering
• PC-controlled: switching of modes of measurement is performed by automatic switching of the components inside the system

Three scanning modes:

• Laser beam scanning over fixed sample surface with XY scanner
• Sample transfer by means of XY automated stage relative to the fixed laser beam
• Multiplexed mode for panorama imaging with a high speed and high spatial resolution: XY scanner + automated stage

Highly-precise calibration over the wavelengths: better than ±0,002nm due to an embedded calibration lamp as a source of reference lines for automated operative calibration of the monochromator-spectrograph.
Block, rigid framing provides a high temporal and thermal stability.

Polysterene balls of various diameter (F-CARS, 3045 cm-1)

3D CARS image of liquid crystal 8CB structure on resonant frequency 2236 cm^-1

Multimodal CARS/TPEF image of growing cancer cells HeLa: DNA/RNA/Proteins/Lipids colored

Selective imaging of MIA-PaCa pancreatic human cancer cell for resonance 2845 cm -1 C-H bound (C-H aliphatic stretch). Selective lipids visualization.

3D image of a cell

References:
Dr. A. V. Kachynski,
The Institute for Lasers, Photonics,
and Bio-photonics,
State University of New York at Buffalo