Reconstruction of coherent anti‐Stokes Raman scattering signals generated by means of laser pulses with asymmetric amplitude and phase. (24th June 2019)

• Record Type: Journal Article
• Authors: Marrocco, Michele; Polli, Dario; Marrocco, Michele; Zheltikov, Aleksei; Kiefer, Johannes
• Is Part Of: Journal of Raman spectroscopy. Volume 50:Number 9(2019)
• Page Start: 1329
• Page End: 1338
• Publication Date: 2019-06-24
• Subjects: coherent anti‐Stokes Raman scattering -- laser spectroscopy -- ultrafast laser physics; Raman spectroscopy -- Periodicals; 535.846
• DOI: 10.1002/jrs.5646
• Languages: English
• ISSNs: 0377-0486

Abstract

Abstract: Time and frequency asymmetries in ultrashort chirped laser fields might appear as a consequence of dispersive propagation, pulse shaping techniques, or generation of auxiliary light pulses needed in nonlinear optics. Here, we try to find an answer to the question of how to solve analytically coherent anti‐Stokes Raman scattering (CARS) under asymmetric conditions of chirped femtosecond laser pulses. The approach breaks in two parts. One for the field amplitudes and the other for the phases. The former revolves around Gaussian dependences that, besides being rather common in ultrashort laser physics, can be arranged and mixed to reproduce spectrally asymmetric laser amplitudes. The latter is limited to field phases with cubic frequency dependence (i.e., second‐order chirp) whose asymmetry is simulated by adding a linear term to the quadratic phase. Both approximations for amplitudes and phases of the three laser pulses are mandatory to guarantee the solution to the complexity posed by the CARS problem. Comparisons with known experimental and numerical results support the validity of the model. Abstract : Amplitude and phase asymmetries in ultrashort chirped laser fields are treated analytically to elaborate coherent anti‐ Stokes Raman signals for N2 molecules useful for thermometric purposes. Field amplitudes are simulated by means of linear combination of Gaussian pulses. Cubic spectral phases are approximated by spectral asymmetries where the cubic dependence is removed. Comparisons with experiments are shown (see the figure where comparisons are made with numerical and experimental results in previous study).