Vibrational imaging provides chemical specificity, which is useful in biological microscopy, and pharmaceutical and material science, especially where other microscopy techniques provide ambiguous results and labels cannot be used. Spontaneous Raman scattering microscopy, while sensitive, is slow. However, its nonlinear counterparts – coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) – can be used for high-speed and high-sensitivity label-free vibrational imaging.
In CARS microscopy, two beams are used to produce radiation at a third wavelength via a vibrational level of the sample. The energy difference between the two beams can be tuned to different vibrational levels, thus providing chemical imaging contrast. The produced CARS signal is at a different wavelength that is usually background-free, which makes its detection relatively simple. However, CARS distorts the vibrational lineshapes and possesses a nonresonant signal component, which complicates chemical attribution. SRS is free from these disadvantages; however, its signal is a small modulation on one of the incoming beams and requires an elaborate detection scheme.
CRONUS-2P is a femtosecond laser providing three simultaneous and synchronized outputs with high repetition rate, high output power, short pulse duration, and GDD control, making it the ultimate source for nonlinear microscopy. Two outputs are independently tunable in the 680 – 960 nm and 960 – 1300 nm ranges, while the third is fixed at 1025 nm. The three simultaneous outputs enable advanced CARS and SRS applications with dual-band imaging, a broader selection of vibrational resonance frequencies, constant-difference dual‑beam tuning, resonant enhancement, and more.
- Watt-level output and high repetition rate
- Two tunable and one fixed output
- Automated GDD control
- Industrial-grade design
- High output stability
- 11, 20, 40, or 76 MHz repetition rate
- < 50 fs pulse duration
- Up to 0.6 µJ pulse energy
- Up to 20 W output power
- Industrial-grade design
- 100 fs – 20 ps tunable pulse duration
- 4 mJ maximum pulse energy
- 20 W maximum output power
- Single-shot – 1 MHz repetition rate
- Automated harmonic generators (up to 5th harmonic)
- 190 – 16000 nm tuning range
- Single-shot – 2 MHz repetition rate
- Up to 80 W pump power
- Up to 2 mJ pump pulse energy
- Completely automated
CARS-imaging guidance for fs-laser ablation precision surgery
T. Meyer, R. Ackermann, R. Kammel, M. Schmitt, S. Nolte, A. Tünnermann, and J. Popp, The Analyst 24 (144), 7310-7317 (2019).
Vibrational spectroscopy and imaging with non-resonant coherent anti-Stokes Raman scattering: double stimulated Raman scattering scheme
D. S. Choi, C. H. Kim, T. Lee, S. Nah, H. Rhee, and M. Cho, Optics Express 16 (27), 23558 (2019).
Microsphere-aided optical microscopy and its applications for super-resolution imaging
P. K. Upputuri, and M. Pramanik, Optics Communications 404, 32-41 (2017).
Chirped time-resolved CARS microscopy with square-pulse excitation
P. K. Upputuri, L. Gong, and H. Wang, Optics Express 8 (22), 9611 (2014).
Super-resolution coherent anti-Stokes Raman scattering microscopy with photonic nanojets
P. K. Upputuri, Z. Wu, L. Gong, C. K. Ong, and H. Wang, Optics Express 11 (22), 12890 (2014).