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Within the last years it has been shown that chemical sensitive linear and non-linear spectroscopy approaches for multi-contrast and multi-parameter imaging of biological and biomedical target structures (e.g. viruses, pathogens, tumor cells, tissue sections, organs etc.) offers great potential for clinical diagnostics and therapy. Here, we review our recent work on transferring spectroscopic approaches...
Microresonator Kerr frequency combs have the potential to revolutionize many aspects of modem technology (e.g. in precision metrology, spectroscopy, as well as telecommunications). In Kerr cavities, stable, low-noise, optical frequency combs often take the form of temporal cavity solitons (CSs): ultra-short optical pulses that persist in driven nonlinear resonators [1]. Recently, studies of CSs under...
Label-free optical microscopy plays an important role in biological research. Coherent Raman microscopy combines three-dimensional resolution and fast image acquisition with molecular selectivity based on the vibrational spectrum of the sample. During the last years stimulated Raman scattering (SRS) microscopy has become an important technique in this framework since it does not display an electronic...
Fibered sources of photon pairs can be easily integrated into future quantum communication networks. However, in silica-core fibres, the broadband spectrum of spontaneous Raman scattering strongly contributes to uncorrelated noise photons degrading the quality of the source. To overcome the problem of the silica Raman scattering, a new architecture was recently proposed, with hollow-core photonic...
A major advantage of solid-state lasers emitting in the 1 μm wavelength range is the possibility of using optical fibers for flexible beam delivery. This is already state of the art in laser material macro-processing with multimode beams. For modern high-brightness lasers with a diffraction-limited beam the guiding is restrained to a few meters or low powers due to nonlinear effects, mainly to Stimulated...
Distributed Raman amplification is an attractive way to improve the OSNR in optical transmission systems. However, this requires profound system knowledge to profit from these potential benefits. Especially in the case of co-directional pumped Raman amplifiers the evolution of the signal powers over the propagation distance is of interest in order to avoid signal distortions. Within the design process...
Raman spectroscopy is the workhorse for label-free analysis of molecules. Here, we show that dense self-organized networks of nanoparticles produced during femtosecond laser can lead to a strong Raman enhancement effect.
Coherent Raman imaging by means of coherent anti-Stokes Raman scattering (CARS) or stimulated Raman scattering (SRS) have been promoted from almost two decades now as efficient label free fast imaging modalities with chemical sensitivity and with a sensitivity orders of magnitude greater than spontaneous Raman scattering [1]. The ability of CARS to detect stable isotope (e.g. deuterium and C13) is...
Hollow-core photonic crystal fibers (HC-PCF) opened new perspectives towards multi-octave comb generation and waveform synthesis using stimulated Raman scattering (SRS) generation in gases introduced in its core [1, 2]. In the transient regime of SRS [3], a short pump pulse combined to a high gain can amplify a few spatial-temporal modes (STM) from the quantum noise. It is even possible to have only...
Electron-phonon scattering and anharmonicity are the dominant mechanisms, that enable to describe the equilibrium phonon properties in graphene [1] and Raman scattering is the main tool for their characterization [2]. In the first tens fs after the photoexcitation, an out of equilibrium distribution of (hot) electron is induced with respect to the (cold) phonon bath. Within a few picoseconds, the...
The use of stimulated Raman scattering (SRS) for Kerr comb generation is very attractive because it allows us to generate long-wavelength light, particularly in the mid-infrared wavelength regime, where the wavelengths are useful for sensing applications. Recently, the generation of comb light and the interaction between transverse modes with the SRS process using a crystalline microcavity have been...
We demonstrate the use of an acousto-optic programmable dispersive filter (AOPDF) as a fast delay line for pump-probe spectroscopy and stimulated Raman scattering. Both of these nonlinear imaging schemes have exhibited potential for various applications including cancer detection.
Coherent Raman scattering microscopy, an emerging imaging technology using nonlinear-optical effects such as coherent anti-Stokes Raman scattering (CARS) or stimulated Raman scattering (SRS), has gained increasing attention because of its highly-sensitive, chemically-specific imaging capability with an intrinsic molecular-vibrational contrast. Despite the recent technical advancements, specific detection...
In the field of pharmaceutical research, confocal Raman microscopy recently attracted a lot of attention for non-invasive and three-dimensional imaging. In contrast to fluorescence microscopy generally requiring bulky labels which often change physicochemical properties of drugs impeding predictive analysis, Raman microscopy is inherently chemically selective. Applications range from drug distribution...
Lead-halide hybrid perovskite crystals have emerged as potentially materials for solar cells due to their power conversion efficiency over 20% [1]. In this work we conduct a comparative study between two hybrids (CH3NH3PbBr3 and CH3NH3Pba3) and an all-inorganic lead-halide perovskite (CsPbBr3). Both have the general ABX3 perovskite formula, with similar band gap (2.2 eV) and similar structural phase...
Recent advances on Surface Enhanced Raman Scattering (SERS) have led to a delicate control of the coupling between extremely-confined plasmonic resonances supported by metallic structures and the vibrational states of molecules. As a consequence, experiments have started to emerge that cannot be easily explained using standard models based on the classical enhancement of the plasmonic fields near...
We present our recent advances on rapid spectro-polarimetry to identify otherwise indistinguishable molecules by polarization effects in multiplex coherent anti-Stokes Raman scattering spectroscopy (CARS).
Fiber based cw laser systems nowadays reach output powers of several kW and often limited by nonlinear effects such as Stimulated Raman Scattering (SRS) [1]. Previously, the influence of the grating spectral width of fiber oscillators on SRS has been investigated [2]. Here we go one step further and compare different seed laser systems that are amplified to a kW level in a single fiber amplifier with...
Stimulated Raman scattering is coherently suppressed if the rate of phonon creation is exactly balanced by the rate of phonon annihilation, a prediction first made by Bloembergen and Shen in 1964 [1]. Viewed classically, this occurs when the fringe patterns created by the interference of pump-Stokes and pump-anti-Stokes signals cancel each other out. It has been recently shown that gas-filled hollow-core...
Raman spectroscopy allows for label-free identification of molecules, retrieving their characteristic vibrational fingerprints. It finds applications in many disciplines, such as biomedical sciences [1]. The cross section of spontaneous Raman scattering is inherently very low, thus hampering its use for high-speed microscopy applications. Coherent Raman scattering (CRS) boosts the signal by many orders...
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