Lipid domains in supported lipid layers serve as a popular model to gain insight into the processes associated with the compartmentalization of biological membranes into so-called lipid rafts. In this paper, we present reproducible tip-enhanced Raman spectra originating from a very small number of molecules in a lipid monolayer on a gold surface, probed by the apex of a nanometer-sized silver t...

Differential pulse-width-pair BOTDA technique is combined with bi-directional Raman amplification and Simplex coding to achieve sub-meter spatial resolution over very long sensing distances. Numerical simulations are used to optimize the power levels of the Raman pumps, avoiding nonlinear effects and pump depletion. Distortions in the Brillouin gain spectrum due to acoustic-wave pre-excitation ...

A vector theory of the stimulated Raman scattering process is developed for describing the polarization effects in fiber-based Raman amplifiers. We use this theory to show that polarization-mode dispersion (PMD) induces large fluctuations in an amplified signal. It is found that PMD-induced fluctuations follow a log-normal distribution. We also discuss the random nature of the polarization-depe...

A pulsed mid-infrared pump at λ=2173 nm is used to demonstrate wideband optical parametric gain in a low-loss 2 cm long silicon photonic wire. Using dispersion engineering to obtain negative second-order (β2) and positive fourth-order (β4) dispersion, we generate broadband modulation instability and parametric fluorescence extending from 1911 nm-2486 nm. Using a cw probe signal to interrogate t...

An applications-oriented review of optical parametric amplifiers in fiber communications is presented. The emphasis is on parametric amplifiers in general and single pumped parametric amplifiers in particular. While a theoretical framework based on highly efficient four-photon mixing is provided, the focus is on the intriguing applications enabled by the parametric gain, such as all-optical sig...

Label-free microscopy with chemical contrast and high acquisition speed up to video-rate has recently been made possible by stimulated Raman scattering (SRS) microscopy. While SRS imaging offers superb sensitivity, the spectral specificity of the original narrowband implementation is limited, making distinguishing chemical species with overlapping Raman bands difficult. Here we present a highly...

introduction: raman spectroscopy, that is a spectroscopic technique based on inelastic scattering of monochromatic light, can provide valuable information about molecular vibrations, so using this technique we can study molecular changes in a sample. material and methods: in this research, 153 raman spectra obtained from normal and dried skin samples. baseline and electrical noise were eliminat...

Raman amplification is a solution for broadband wavelength-division multiplexed (WDM) systems that require fine and reconfigurable gain tuning. However, as the fiber nonlinearity ultimately limits performance of fiber-optic communication systems, accurate models nonlinear interference affecting signal propagation in presence multiple pumps are critical system design. In this study, we propose a...

The transmission characteristics of a Raman-amplified atomic filter that can be used to detect fairly weak signals in free-space quantum-key distribution or laser communications are analyzed and discussed in the coherent and incoherent pump fields respectively. The theoretical model for the calculation of the transmission characteristics of a groundstate Raman-amplified Faraday dispersion atomi...

This paper describes the pumping schemes for ultra-wideband (UWB) WDM transmission using only distributed Raman amplification. By numerical analysis based on Gaussian noise model, we evaluate amplification performances all-Raman UWB-WDM higher-order and/or forward in addition to conventional 1st-order backward pumping. Moreover, discuss effect of gain bidirectional configuration, and clarify th...