Broadband nonlinear vibrational spectroscopy by shaping a coherent fiber supercontinuum

Abstract

Vibrational spectroscopy has been widely applied in different fields due to its label-free chemical-sensing capability. Coherent anti-Stokes Raman scattering (CARS) provides stronger signal and faster acquisition than spontaneous Raman scattering, making it especially suitable for molecular imaging. Coherently-controlled single-beam CARS simplifies the conventional multi-beam setup, but the vibrational bandwidth and nontrivial spectrum retrieval have been limiting factors. In this work, a coherent supercontinuum generated in an all-normal-dispersion nonlinear fiber is phase-shaped within a narrow bandwidth for broadband vibrational spectroscopy. The Raman spectra can be directly retrieved from the CARS measurements, covering the fingerprint regime up to 1750 cm −1 . The retrieved spectra of several chemical species agree with their spontaneous Raman data. The compact fiber supercontinuum source offers broad vibrational bandwidth with high stability and sufficient power, showing the potential for spectroscopic imaging in a wide range of applications. 1929-1960 (2000). 11. Y. Silberberg, "Quantum coherent control for nonlinear spectroscopy and microscopy," Annu. Rev. Phys. Chem. 60(1), 277-292 (2009 Midorikawa, "Single-pulse coherent anti-Stokes Raman scattering microscopy employing an octave spanning pulse," Opt. Express 17 ( "Cross-validation of theoretically quantified fiber continuum generation and absolute pulse measurement by MIIPS for a broadband coherently controlled optical source," Appl.

Limits of coherent supercontinuum generation in normal dispersion fibers

“…In contrast, low temporal coherence associated with large pulse-to-pulse fluctuations often plays a precision or resolution limiting role, for example in modalities using the coherence directly as content in the acquired signal, such as optical coherence tomography [5,6] or coherent antiStokes Raman scattering (CARS) spectroscopy [7]. Since spectral amplitude and phase fluctuations also translate into temporal jitter, ultrafast photonics applications usually demand SC sources with a high degree of coherence to enable, for example, beam synchronization and extraction of time-resolved information in multi-beam pump-probe techniques, nonlinear pulse compression, multimodal bio-photonic imaging, or coherent control experiments [8][9][10][11][12][13][14][15].…”

Telecom to mid-infrared spanning supercontinuum generation in hydrogenated amorphous silicon waveguides using a Thulium doped fiber laser pump source

“…Nonlinear optics provides a good way to generate new optical frequencies spaced a predictable and controllable distance from a strong pump frequency and is thus well-placed to take advantage of commercially available sources at shorter wavelengths to generate mid-IR spatial and/or temporally coherent radiation. Supercontinuum generation (SCG) has received a lot of attention from researchers in recent years [1] because of the breadth of its potential applications such as in optical coherence tomography [2], wavelength division multiplexing in telecommunications [3,4], in optical sensing [5] and in spectroscopy [6,7]. A lot of the work in supercontinuum generation has focused on the use of photonics crystal fibers [2].…”

Multimodal spectral focusing CARS and SFG microscopy with a tailored coherent continuum from a microstructured fiber

“…To avoid the need for a 10 fs oscillator for SF-CARS, methods using Stokes and pump carved from SC pulses generated in so-called microstructured fibers (MOFs) have been developed at significantly lower cost and are now widely used for SC pumped bioimaging [27,[30][31][32]. The SC in fibers such as the femtoWHITE 800 fiber from NKT is ordinarily generated in the anomalous dispersion regime, where the soliton fission threshold, above which the SC pulse breaks into multiple pulses, limits the coherence and reduces the effectiveness for exciting CARS signals [33].…”