Ultrafast Laser Spectroscopy / Imaging


  • High Peak Powers

          – Nonlinear Phenomena

  • Ultrashort Pulses

           – Collision-Free Measurements
           – Time Dynamics
           – Spectral Bandwidth

  • High Repetition Rates

           – Data-Acquisition Bandwidth
           – Time Series, PSDs, Correlations

  • Potential to Simplify NL Spectroscopic Measurements

           – CARS Thermometry and Species Detection with One Laser Beam
           – Pulse-Shaping for Species Selective Detection
           – Collision-Independent Species Concentration using LIF
           – Interference-free Atomic Species Concentration Measurements


High-bandwidth for Multi-Photon Excitation Advantages

1. Nanosecond vs Femtosecond Raman excitation of N2

[S. Roy et al., Progress in Energy and Combustion Science 36, 280-306 (2010)]

2. For Multi-photon Absorption

[Patnaik et al., Plasma Sources Science and Technology 26, 103001 (2017)]


1) kHz-rate Femtosecond (fs) Coherent anti-Stokes Raman Scattering (CARS) Line Imaging

[Optics Letters 36 (21), 4182-4184 (2011)]


2) Two-Color fs Fully Resonant Electronically Enhanced CARS (FREE-CARS)

[Stauffer et al., Journal of Chemical Physics 145 (12), 124308 (2016)]


2.a  FREE-CARS: Single-shot temperature and [OH] in laminar C2H4–air flame

2.b  FREE-CARS: Detection of minor species (for example NO)

3) Single-Shot 100-kHz picosecond-CARS in H2/N2 turbulent jet diffusion flame (Re = 10,000)

[Roy et al., Optics Letters 40 (21), 5125-5128 (2015)]


4) 1-kHz, Single-Shot 2D CARS of O2

[Miller at al., Optics Express 24 (22), 24971-24979 (2016)]


5) Fs Laser-Based Two-Photon Absorption Laser-Induced Fluorescence (TALIF) Imaging of H-Atom

[Optics Letters 37 (15), 3051-3053 (2012)]

Shorter pulses improve two-photon excitation and reduce single-photon photodissociation

Longer pulse excitation for TALIF produces very high photolytic interference


6) kHz-rate Fs-TALIF Imaging of CO in a Driven Flame

[Richardson et al., AIAA Aerospace Sciences Meeting, AIAA SciTech Forum, (AIAA 2018-1773)]

High peak intensity; low pulse energy

Minimal photolytic CO production