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Quantum state engineering has seen important developments over the last decade. The use of hybrid protocols, combining the discrete and continuous variables of light, can achieve high detection efficiencies, making them a good candidate for the production of non-classical states. Schrödinger cat states (SCSs), superpositions of two coherent states |α〉 in phase opposition (ψcat) 〉 |α〉 ± |-α〉), constitute...
The main limitation of second-order nonlinear optical materials is the requirement of non-centrosymmetry within the electric-dipole approximation. However, higher multipole effects (such as magnetic-dipole and electric-quadrupole) do not suffer from such restriction. Thus, multipole effects can provide an interesting path towards novel second-order materials. Although multipole effects have been already...
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...
The use of optical frequency combs (FC) for high precision measurements is limited by fluctuations of the comb structure [1]. The FC fluctuations can be modelled as uncoupled noise modes associated with a few global parameters namely power, central wavelength, carrier-envelope offset (CEO) phase, repetition rate, dispersion [2, 3]. However, the correlations between phase and amplitude noises, which...
Nonlinear effects in cavities and microresonators attract nowadays considerable attention, mainly because they allow generation of equidistant optical frequency combs [1] that are desirable for a number of applications in diverse areas of science. In proper regime, phases of different comb lines may be synchronized leading to formation of stationary soliton states moving along the microresonator....
Due to a strong light absorption by metals, it is believed that plasmonic nanostructures cannot be used for generating intensive radiation harmonics in the UV spectral range. We present results of investigation of the nonlinear optical interaction of laser radiation with a single gold nanostructure in the geometry of the Split-Hole Resonator (SHR) [1, 2] under the-state-of-the-art experimental realized...
State-of-the-art optical atomic clocks have attained short-term fractional frequency stabilities in the low 10 range [1, 2]. This has been made possible thanks to improved performances of the clock lasers, which are pre-stabilized using ultra-stable Fabry-Perot (FP) resonators [3] Many of the last-generation optical clocks rely on frequency doubling via second harmonic generation (SHG) to produce...
The potential of Optical Frequency Combs (OFC) as wide bandwidth, stable, coherent, multimode sources is widely recognized and has applications in various fields, such as metrology, spectroscopy, optical communications or biomedicine. The dual optical frequency comb approach relies on the use of a second local oscillator (LO) comb with slightly different repetition frequency. This LO is then heterodyned...
In recent years, the fabrication, structural modification and characterisation of nanostructured materials have gained a great deal of attention due to their distinctive properties and potential use in technological applications. Glass containing silver (Ag) nanoparticles (NP), or Metal-Glass Nanocomposite (MGN), is routinely used as high-contrast optical polarisers [1], and has been recently shown...
In this work we present an experimental and theoretical study on high-order hyper-Rayleigh scattering (HRS). This process also called harmonic light scattering, is an incoherent variant of harmonic generation process which occurs in bulk crystals. In general, HRS is addressed in the literature to the lowest-order nonlinear (NL) processes of molecules or nanoparticles, i.e., second harmonic scattering...
Molecular precision spectroscopy opens new perspectives on tests of fundamental laws of physics and of fundamental constants variation [1]. The mid infrared (IR) is a key region for molecular spectroscopy, and the efforts towards the development of versatile, spectrally pure, and tunable coherent sources in this region have been constantly growing in the last decade. A convenient way to generate a...
High-order harmonic generation (HHG) in atomic gases is one of the key phenomena in strong-field laser-matter interactions, playing a central role in optical physics and rapidly growing attosecond technologies. When applied to solid materials [1-3], approaches of strong-field physics are subject to natural limitations, related to absorption and much lower laser damage thresholds of solids. As a reward,...
High repetition rate femtosecond VIS radiation has been generated in optical parametric oscillators (OPOs) either by generating VIS light through intra-cavity SHG or SFG [1, 2] or in VIS OPOs using frequency-doubled Ti:sapphire as a pump laser [3, 4]. Recently, we also demonstrated the generation of VIS light via efficient intra-cavity SFG in NIR NOPO pumped by a thin disk laser [5]. In this work,...
Over the past decade high-resolution and broadband spectroscopy has received a major boost from the advent of optical frequency combs (OFCs) [1, 2]. Direct frequency comb spectroscopy (DFCS) exploits high-speed multiplexing approaches in order to simultaneously detect a massive set of extremely accurate channels, allowing for ultra-broadband and high speed spectroscopic investigations [3, 4]. Here...
Laser Scanning Microscopy (LSM) techniques play in current days a key role in imaging and characterizing biological tissues. Among these, Multiphoton Microscopy (MPM), with its two main variants: Two-Photon Excitation Fluorescence (TPEF) and Second Harmonic Generation (SHG), has emerged as a powerful tool to investigate unprocessed tissues with resolution and detail comparable to standard histology...
An optical frequency comb can generate hundreds of individual comb lines which can be employed in wavelength division multiplexing systems [1], thus reducing the cost, footprint, power consumption and system complexity when compared to using multiple lasers. However to date, comb-based communications have been limited to lower modulation formats more tolerant to phase noise, due to poor carrier to...
Optical frequency comb spectroscopy in the mid-infrared fingerprint region combines broad spectral bandwidth with high detection sensitivity and allows simultaneous detection of trace amounts of many molecular species. We have recently demonstrated a continuous-filtering Vernier spectrometer based on a mid-infrared optical frequency comb and an enhancement cavity for fast and sensitive detection of...
In 2011, Dual-chirped optical parametric amplification (DC-OPA) [1] had been proposed theoretically as one of the OPA method. Y. Fu et al. experimentally demonstrated DC-OPA in 2015 and generated 10-mJ IR pulses energy in 1–2 um region [2, 3]. At present, DC-OPA method is ready to extend up to THz region [4].
A high quality factor (Q) microcavity is an efficient device for generating a Kerr comb via a four-wave mixing process inside the cavity [1]. Kerr comb platforms are candidates for such applications as optical frequency combs, optical communications, arbitrary waveform generation, and microwave oscillators. Although a silica toroid microcavity (Fig. 1(a)) also has good characteristics for Kerr comb...
A new branch of nonlinear nanophotonics based on high refractive index dielectric nanoparticles is emerging [1]. The unique large resonant enhancement of both electric and magnetic fields associated with very low dissipative losses considerably increases optical interactions at sub-wavelength scales opening new unexplored functionalities. Recently, AlGaAs nanodisks enabled second harmonic generation...
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