Hybrid Coherent Anti-Stokes Raman Scattering
Advanced Diagnostics Navigation
- Atomic and molecular species, positive and negative ions
- Laser-Induced Fluorescence (LIF) and Two-Photon Absorption LIF (TALIF)
- Characterization of plasma, chemical composition and dynamic behavior
- Electron velocity distribution function, gas flow velocity and temperature
- Electric field and space potential
- Nanoparticle Diagnostics
- Surface Diagnostics
- Surface Second Harmonic Generation (SHG)
- Electron-induced Secondary Electron Emission and Surface Charging Measurements
Hybrid Coherent Anti-Stokes Raman Scattering (Hybrid CARS)
CARS has been proven to be a very useful spectroscopic tool for measuring Raman rotational and vibrational spectra. The fs/ps hybrid CARS diagnostic developed at Princeton [1,2] allows for in-situ single shot coherent Raman spectroscopy at kHz rate. The laser source is a Spectra Physics Solstice Ace equipped with an Optical Parametric Amplifier, delivering 1 mJ of 100 fs pulses at 1 kHz in the 1400-1800 nm NIR region for the pump and Stokes beams. The probe beam is obtained by spectrally filtering the 800 nm fundamental. The CARS signal is recorded by a Princeton Instruments imaging spectrometer equipped with a Hamamatsu C9100 cooled EMCCD camera for trace detection, or with an intensified PCO DIMAX HD fast camera for temperature measurements at 1 kHz. This hybrid technique combines the robustness of frequency-resolved CARS with the advantages of time-resolved CARS spectroscopy. Using this hybrid technique, we have demonstrated real-time standoff detection of molecular species based on their vibrational spectra, with high sensitivity and selectivity [3-5]. We can utilize this powerful diagnostic for measuring concentration of negative ions in the low-temperature gaseous plasma and spectroscopically investigate the nanoparticle dynamics. From our trace detection limit using CARS to measure sub-ng of targets in real-time , we estimate to be able to collect the coherent Raman spectra from C60 at densities less than 1011 cm-3. Furthermore, the hybrid CARS setup allows for real-time non-equilibrium temperature measurements in gases and plasmas by simultaneously recording the rotational and vibrational spectra in a single shot with kHz repetition rate. Our diagnostic has the capability of single-shot non-equilibrium temperature measurements with 1kHz rate at densities below 1 Torr [6,7]. This allows for measurement of minor species down to 0.1% of an atmospheric pressure mixture. Additionally, using the LINE-CARS approach [2,5] to record 1-D images in a single shot, we can also spatially resolve mixtures of gases.
- D. Pestov et al., Science 316, 265 (2007).
- A. Dogariu, patent US9163988 (2015).
- A. Dogariu, A. Goltsov, D. Pestov, A. V. Sokolov, and M. Scully, J. Appl. Phys. 103, 036103 (2008).
- A. Dogariu, A. Goltsov, and M. O. Scully, J. Biomed. Opt. 13, 54004 (2008).
- A. Dogariu and A. Pidwerbetsky, Proc. SPIE 8358-27, (2012).
- A. Dogariu, L. E. Dogariu, M. S. Smith, J. Lafferty, and R. B. Miles, AIAA SciTech 2019 Forum, 1089 (2019).
- A. Dogariu, L. Dogariu, M. Smith, B. McManamen, J. Lafferty, and R. Miles, “Velocity and Temperature Measurements in Mach 18 Nitrogen Flow at Tunnel 9,” AIAA SciTech 2021 Forum, 0020 (2021).