arXiv subjects

Malik Nafa

Publications and source records attributed to Malik Nafa.

5 recordsLinked to original sources

arXiv2024

Exploitation of the nonresonant background of Multiplex-Coherent anti-Stokes Raman Scattering for label-free discrimination of proteins

We propose a novel approach using Multiplex-Coherent Anti-Stokes Raman Scattering (M-CARS) for la-bel-free discriminations in biomedical tissues. The strategy is based on the evaluation of the contrast be-tween resonant and nonresonant contributions in a M-CARS hyperspectral dataset, and tested to identify and differentiate thin actin filaments from thick myosin filaments in muscle tissue without any labeling. First step consists in ensuring knowledge of the spatial regions containing thick myosin filaments thanks to its endogenous second harmonic signal, deducing expected location for thin actin filaments between myosin filaments. The ratio of resonant and nonresonant contributions for each pixel of the hyperspectral image allows then to discriminate actin from myosin filaments, whose localization is in accordance with the SHG probing. This qualitative imaging represents a proof of principle for highlighting and discriminat-ing purposes in biological microscopy, thanks to the difference in the nonlinear properties of the related proteins. This paves the way for considering label-free imaging through a competition between two third-order nonlinear signatures.

physics.med-ph↗

arXiv2021

Direct observation of terahertz frequency comb generationin difference-frequency quantum cascade lasers

Terahertz quantum cascade laser sources based on intra-cavity difference frequency generation from mid-IR devices are an important asset for applications in rotational molecular spectroscopy and sensing, beingthe only electrically pumped device able to operate in the 0.6-6 THz range without the need of bulky andexpensive liquid helium cooling. Here we present comb operation obtained by intra-cavity mixing of adistributed feedback laser at λ = 6.5 μm and a Fabry-Pérot device at around λ = 6.9 μm. The resultingultra-broadband THz emission extends from 1.8 to 3.3 THz, with a total output power of 8 μW at 78K.The THz emission has been characterized by multi-heterodyne detection with a primary frequencystandard referenced THz comb, obtained by optical rectification of near infrared pulses. The down-converted beatnotes, simultaneously acquired, confirm an equally spaced THz emission down to 1 MHzaccuracy. In the next future this setup can be used for Fourier transform based evaluation of the phaserelation among the emitted THz modes, paving the way to room-temperature, compact and field-deployable metrological grade THz frequency combs.

physics.optics↗

arXiv2020

Quantum Cascade Laser Based Hybrid Dual Comb Spectrometer

Four-wave-mixing-based quantum cascade laser frequency combs (QCL-FC) are a powerful photonic tool, driving a recent revolution in major molecular fingerprint regions, i.e. mid- and far-infrared domains. Their compact and frequency-agile design, together with their high optical power and spectral purity, promise to deliver an all-in-one source for the most challenging spectroscopic applications. Here, we demonstrate a metrological-grade hybrid dual comb spectrometer, combining the advantages of a THz QCL-FC with the accuracy and absolute frequency referencing provided by a free-standing, optically-rectified THz frequency comb. A proof-of-principle application to methanol molecular transitions is presented. The multi-heterodyne molecular spectra retrieved provide state-of-the-art results in line-center determination, achieving the same precision as currently available molecular databases. The devised setup provides a solid platform for a new generation of THz spectrometers, paving the way to more refined and sophisticated systems exploiting full phase control of QCL-FCs, or Doppler-free spectroscopic schemes.

physics.optics↗

arXiv2019

Fully phase-stabilized quantum cascade laser frequency comb

Optical frequency comb synthesizers (FCs) [1] are laser sources covering a broad spectral range with a number of discrete, equally spaced and highly coherent frequency components, fully controlled through only two parameters: the frequency separation between adjacent modes and the carrier offset frequency. Providing a phase-coherent link between the optical and the microwave/radio-frequency regions [2], FCs have become groundbreaking tools for precision measurements[3,4]. Despite these inherent advantages, developing miniaturized comb sources across the whole infrared (IR), with an independent and simultaneous control of the two comb degrees of freedom at a metrological level, has not been possible, so far. Recently, promising results have been obtained with compact sources, namely diode-laser-pumped microresonators [5,6] and quantum cascade lasers (QCL-combs) [7,8]. While both these sources rely on four-wave mixing (FWM) to generate comb frequency patterns, QCL-combs benefit from a mm-scale miniaturized footprint, combined with an ad-hoc tailoring of the spectral emission in the 3-250 μm range, by quantum engineering [9]. Here, we demonstrate full stabilization and control of the two key parameters of a QCL-comb against the primary frequency standard. Our technique, here applied to a far-IR emitter and open ended to other spectral windows, enables Hz-level narrowing of the individual comb modes, and metrological-grade tuning of their individual frequencies, which are simultaneously measured with an accuracy of 2x10^-12, limited by the frequency reference used. These fully-controlled, frequency-scalable, ultra-compact comb emitters promise to pervade an increasing number of mid- and far-IR applications, including quantum technologies, due to the quantum nature of the gain media [10].

physics.optics↗

arXiv2015

High brightness diode-pumped organic solid-state laser

High-power, diffraction-limited organic solid-state laser operation has been achieved in a vertical external cavity surface-emitting organic laser (VECSOL), pumped by a low-cost compact blue laser diode. The diode-pumped VECSOLs were demonstrated with various dyes in a polymer matrix, leading to laser emissions from 540 nm to 660 nm. Optimization of both the pump pulse duration and output coupling leads to a pump slope efficiency of 11% for a DCM based VECSOLs. We report output pulse energy up to 280 nJ with 100 ns long pump pulses, leading to a peak power of 3.5 W in a circularly symmetric, diffraction-limited beam.

physics.optics↗