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Surface-enhanced Raman spectroscopy is a promising method for analysis of gas media composition. In this work we present an analysis of resonant metal-dielectric holographic gratings providing an essential local field enhancement due to excitation of the surface plasmon-polaritons. It is shown that structure parameters yielding an optimum far-field resonance excitation are not necessarily correspond to optimum local field maximum.

Dielectric nanoparticles, and silicon nanoparticles in particular [1,2], are becoming increasingly promising for various applications in photonics, nonlinear optics, optomechanics, and medicine. Plenty of applications exploit the benefits of low-loss Mie resonances, exhibited in the optical range by silicon nanoparticles with sizes of the order of 200 nm. The frequencies of the resonant Mie modes are determined by the size and shape of the particles. However, many of the fabrication techniques result in a polydisperse mixture of different sizes and shapes, and prompt for a post-processing to provide a uniform output. Having an entirely optical tool for such separation [3,4] is highly desirable for sterile, hazardous or highly dynamic microfluidic environments. Following our recent publication [4], in this contribution we present the calculated optical forces acting on silicon nanoparticles in aqueous environment, analyse their potential for optical sorting in a number of schemes, and discuss the experimental implementation of the proposed methods in our setup. The optical forces acting on silicon nanoparticles are shown to reveal their substantial dependence on the particle size. This dependence results in different velocities of the light-driven drift of the nanoparticles, depending on their size and the frequency of the incident light. We propose to employ these features to realise optical sorting, according to the following scenarios. First, we use two counter-propagating beams of different wavelength, which move particles of different sizes in opposite directions; by varying the intensity ratio between the two beams, different subsets of the particle sizes can be separated. A similar approach has been implemented for plasmonic particles [3]. Second, we suggest to impose two counter-propagating beams upon a uniform flow of a disperse mixture, which results in the particles of different sizes being pushed along different directions in space, so that an efficient angular separation is possible within certain size ranges. Third, we propose an efficient angular separation in an all-optical way, by directing the two beams at an angle. This scenario offers an efficient angular separation without any imposed flow. In this work, we consider two laser beams with wavelengths of 532 and 638 nm. For this particular case, angular sorting scheme provides a unique size-angle dependence, yielding up to 70° span of deflections, in the size ranges of 120–160 nm, 190–220 nm, and a few smaller sets. We demonstrate that the proposed angular sorting techniques are robust against the Brownian motion, requiring a run of about 100 μm to achieve a 10-nm distinction in size, while using moderate (0.1 W) power. Finally, we consider the forces acting on silicon nanoparticles in the evanescent wave illumination and show that the proposed methods can be applied for a broad size dimensions using p-polarised light. [1] Evlyukhin A.B., et al. Nano Lett. 12, 3749–3755 (2012). [2] Kuznetsov A.I., et al. Sci. Rep. 2, 492 (2012). [3] Ploschner M., et al. Nano Lett. 12, 1923–1927 (2012). [4] Shilkin D., et al. ACS Photonics 4, 2312–2319 (2017).

We designed semiconductor metasurfaces comprised of rectangular arrays of all-Si antennas exhibiting sharp transmission dips. The sizes and periodicities of the antennas were shown to control the spectral positions and linewidths of the corresponding antenna resonances. The designed resonant metasurfaces were fabricated on a 600-nm-thick silicon-on-sapphire substrate using electron beam lithography, hard mask deposition, and inductively coupled HBr plasma etching. Multiple areas with different antenna sizes were defined on the same substrate. The samples were characterized with a FTIR system under normal incidence and paraxial beam configuration. The spectra revealed transmission dips in the spectral range of 3–4 μm, with the central wavelengths corresponding to the local simulated field enhancements of Eloc = 10–15. The metasurfaces were irradiated by a train of femtosecond laser pulses from a supercontinuum-based mid-IR optical parametric amplifier (OPA) pumped by a Ti:Sapphire amplifier. The incoming 200 fs mid-IR pulses, centered at 3.6 μm, had a maximum fluence of 60 mJ/cm2. The transmitted third harmonic radiation was refocused on and detected by an InGaAs detector based short wave-IR spectrometer. For pump–probe experiments, the residual near-IR 782 nm beam was split off from the output of the OPA, sent through a delay line, and focused at the sample collinearly to the mid-IR beam. Using a home-built calibrated mid-IR spectrometer based on a blazed diffraction grating and a mid-IR camera (Electrophysics PV320), we observed a pump-dependent blue-shifting and eventual disappearance of the resonant dips, accompanied by the reduction of the third harmonic generation.

We develop a new avenue to creating the optical spectrometer for the Guillermo Haro astrophysical observatory (Mexico), which combines specifically progressed prism spectrometer with modern acousto-optical approach in the frame of a joint instrument. This schematic arrangement includes two principal novelties. First, we exploit recently developed acousto-optical nonlinearity of the two-phonon light scattering in crystals with linear acoustic losses, which admits an additional physical degree of freedom. This effect allows us to use nonlinear acousto-optical effect for linear processing of optical signals in parallel regime within all the visible range. Similar effect is based on the possibility for tuning the frequency of elastic waves and admits the nonlinear apodization improving the dynamic range. Secondly, we are using the cross-disperser technique with acousto-optical processing for the first time to our knowledge. Additionally, the acousto-optical spectrometers can provide almost 100% efficiency in the acousto-optical interaction in the optimized regime. In the case of 4% Mg doped LiNbO 3 crystal the absorption edge can be shifted down to 370 nm for limited intensity of incoming light. The observation window of optical spectrometer in that observatory is ~ 9 cm, so that the theoretical estimations of maximal performances for a low-loss LiNbO3-crystal for this optical aperture at 405 nm give the spectral resolution 0.0523 A, resolving power 77,400, and number of spots 57,500. The illustrative proof-of-principle experiments with available for us 6-cm LiNbO 3 -crystal have been performed and demonstrated the spectral resolution 0.0782 A at 405 nm and resolving power 51,790.

We present a laboratory high-aperture monochromator-reflectometer employing laser-plasma radiation source and three replaceable Schwarzschild objectives for a certain range of applications in the soft X-ray spectral waveband. Three sets of X-ray multilayer mirrors for the Schwarzschild objectives enable operation of the reflectometer at the wavelengths of 135, 171 and 304 A, while a goniometer with three degrees of freedom allows different measurement modes. We have used the facility for a laboratory CCD calibration at the wavelengths specified. Combined with the results of the CCD sensitivity measurements conducted in the VUV spectral waveband, the total outcome provides a more comprehensive understanding of the CCD effectivity in a wide spectral range.

The study of nonlinear effects with high-index dielectric nanoparticles is emerging as a promising alternative to plasmonic systems usually utilized for nonlinear nanophotonics, due to negligible Ohmic losses and low heating in combination with multipolar radiation characteristics of both electric and magnetic nature. In this contribution, we discussed novel nonlinear-optical effects, such as enhanced second- and third-harmonic generation in silicon nanodisks excited in the spectral range close to the magnetic dipole resonance of the individual disk. Each of the nanodisks exhibits both electric and magnetic Mie-type resonances that are shown to affect significantly their nonlinear response. We have observed the third- harmonic radiation intensity that is comparable to that of a bulk silicon slab and demonstrated a pronounced reshaping of the third-harmonic spectra due to interference of the nonlinearly generated waves augmented by an interplay between the electric and the magnetic dipolar resonances. We have also demonstrated all-optical switching of femtosecond laser pulses passing through subwavelength silicon nanodisks at their magnetic dipolar resonance. In z-scan experiments, we have observed a modulation of up to 60% and a spectral resonance shift of 6 nm when pumping the nanostructure at picojoule-per-disk powers. Third-harmonic generation from silicon nanodisks arranged in the form of quadrumers or trimer oligomers with varying distance between the nanoparticles is studied.

Thin films of hydrogenated amorphous silicon were grown on cover glasses by PECVD in an Oxford PlasmaLab System 100. The thickness of the films and their linear optical properties were characterized by J.A. Woollam Co. Spectroscopic Ellipsometer M-2000D. The follow-up procedure was to spin coat the negative tone ma-N 2403 electron-beam resist over the film, and expose the resist using an electron-beam lithography system (Raith 150). The exposed film was developed and brought to the reactive ion etching facility. We performed conventional apertureless z-scan and I-scan measurements. A train of femtosecond laser pulses form a Coherent Micra 5 laser with an output mean power of 250 mW passed through a precompressor for a negative chirp. A thin-film nanoparticle polarizer (ThorLabs LPVIS050) and a Glan laser-grade polarizer were used to adjust the fluence values in the range of 0.1–10 mJ/cm2. For the pump-probe measurements, a train of femtosecond laser pulses form the laser passed through a pre-compressor for a negative chirp. The pulses were split into two; the resulting mean power values of pump and probe beams at the sample site were approximately 40 mW and 1.5 mW, respectively. The pulses were measured to have 45 fs intensity autocorrelation FHWM duration, and a spectral FWHM width of 19 nm, resulting in a time-bandwidth product of 0.4. Focusing through a silica lens pair achieved waists of roughly 30 μm in diameter, resulting in modest pump fluence values of approximately 30 μJ/cm2, a pump pulse energy of 0.25 nJ, and per-disk deposited energy of 13 fJ. The third-harmonic generation experiment description can be found as the supplementary information of the following publication: http://pubs.acs.org/doi/abs/10.1021/nl503029j

We consider the collinear backward light scattering as one of potential physical mechanisms for creating an advanced collinear acousto-optical filter with significantly improved spectral resolution. Within co-directional crystalline collinear acousto-optical filters, the resolution is inversely proportional to the material’s birefringence, which is ~0.1 in the best case of LiNbO3-crystal. For the backward light scattering this parameter is replaced by the twice refractive index, so that the gain achieves > 45 times in LiNbO3-crystal. Thus, one can expect the resolution ~0.002 A instead of the value ~0.1 – 0.2 A recently obtained by us experimentally for co-directional geometry in that crystal. Moreover, the collinear backward light scattering can be implemented in an extended amount of available materials. However, the main limitation for applying the phenomenon is the acoustic attenuation in ultra-high frequency range peculiar to the materials for acousto-optical filters. Linear acoustic attenuation reduces the length of acousto-optical interaction and limits the spectral resolution. At an initial stage, our studies are concentrated on physical aspects of this phenomenon as well as on possibilities of its application to creating the acousto-optical filters of a high resolution. In particular, the frequency band-shapes of the scattered light intensity exhibit a tendency to specific acousto-optical nonlinearity, i.e. to more and more rectangular profile as the acoustic power density grows. Results of this analysis confirm the above-noted estimations for a triplet of trigonal acousto-optical crystals, having possibly lower acoustic attenuation.

We develop a multi-band spectrometer with a few spatially parallel optical arms for the combined processing of their data flow. Such multi-band capability has various applications in astrophysical scenarios at different scales: from objects in the distant universe to planetary atmospheres in the Solar system. Each optical arm exhibits original performances to provide parallel multi-band observations with different scales simultaneously. Similar possibility is based on designing each optical arm individually via exploiting different materials for acousto-optical cells operating within various regimes, frequency ranges and light wavelengths from independent light sources. Individual beam shapers provide both the needed incident light polarization and the required apodization to increase the dynamic range of a system. After parallel acousto-optical processing, data flows are united by the joint CCD matrix on the stage of the combined electronic data processing. At the moment, the prototype combines still three bands, i.e. includes three spatial optical arms. The first low-frequency arm operates at the central frequencies ~60-80 MHz with frequency bandwidth ~40 MHz. The second arm is oriented to middle-frequencies ~350-500 MHz with frequency bandwidth ~200-300 MHz. The third arm is intended for ultra-high-frequency radio-wave signals about 1.0-1.5 GHz with frequency bandwidth

Regime of effective non-collinear acousto-optical interaction with tangential phase matching had been identified and previously observed only in two limiting cases: in tellurium dioxide (TeO 2 ) at low acoustic frequencies (~60 MHz) and in rutile (TiO 2 ) at ultra-high frequencies (~5 GHz). Both these limits are motivated by optical properties of the chosen materials. Low frequencies in TeO 2 admit designing a wide-aperture acousto-optical cell, but limit the frequency bandwidth. While an acousto-optical cell made of TiO 2 has very small aperture and exhibits low spectral resolution due to the effect of linear acoustic attenuation. Instead of those limits, we propose an advanced regime of the anomalous acousto-optical interaction with tangential phase matching, which allows us varying the frequency range and optimizing all the performances (for instance, the spectral resolution) of a wide-aperture acousto-optical cell made of the chosen crystal, as the case requires. Recently, we had suggested and successfully tested experimentally the revealed additional degree of freedom, i.e. the action of the tilt angle within the refractive indices ellipsoids to manipulate by the performances of crystalline acousto-optical cells. Now, we consider an opportunity of refining this additional degree of freedom within those ellipsoids of crystalline acousto-optical cell through some declination of the acoustic beam. For our investigations, the lithium niobate (LiNbO 3 ) and rutile (TiO 2 ) crystals of about 5 cm length, operating with the slow-shear acoustic mode along the acoustic axes had been selected. The needed theoretical analysis, numerical estimations, and 3D-vector diagrams have been developed to reveal potential benefits of the proposed technique.

Conventionally, all-optical switching devices made out from bulk silicon and other semiconductors are limited by free-carrier relaxation time which spans from picoseconds to microseconds. In this work, we discuss the possibility to suppress the undesired long free-carrier relaxation in subwavelength dielectric nanostructures exhibiting localized magnetic Mie resonances. Numerical calculations show the unsymmetrical modification of the transmittance spectra of the nanodisks due the free carriers photo-injection. Such a spectral dependance allows to control temporal response of the nanostructure by varying the laser pulse spectum.

Performances of any system for data processing based on acousto-optical technique are mainly determined by parameters of the acousto-optical cell (AOC) exploited within the schematic arrangement. Here, basic properties of the AOC, involved into a novel processor for precise optical spectrum analysis dedicated to modern astrophysical applications, are considered. Because potential applications of this processor will be focused on investigations in extra-galactic astronomy as well as studies of extra-solar planets, an advanced regime of the non-collinear two-phonon light scattering has been elaborated for spectrum analysis with significantly improved spectral resolution. Under similar uprated requirements, the AOC, based on that specific regime in the calomel (Hg 2 Cl 2 ) crystal, had been chosen, and its parameters were analyzed theoretically and verified experimentally. Then, the adequate approach to estimating the frequency/spectral bandwidth and spectral resolution had been developed. The bandwidth was calculated and experimentally realized with the additionally involved tilt angle of light incidence, allowing variations for acoustic frequencies. The resolution was characterized taking into account its doubling peculiar to the nonlinear two-phonon mechanism of light scattering. Proof-of-principle experiments were performed with the calomel AOC of 52 mm optical aperture, providing ~94% efficiency in the transmitted light due to the slow-shear acoustic mode of finite amplitude (the acoustic power density ~150 mW/mm 2 ) with the velocity of 0.347×105 cm/s at the radio-wave acoustic frequency ~71 MHz. As a result, we have obtained the spectral resolution

Our work is devoted to the collinear acousto-optical filter governed by the acoustic waves of finite amplitude. It represents a novel bulk-optical component, namely, the dispersive element for optical spectroscopy. This filter is based on specifically doped lithium niobate single crystal that unexpectedly works in the near ultraviolet range as well as this material usually works in the visible range. We examine the phenomena affecting the filter transmission efficiency and its resolution, i.e. the light-induced absorption and photorefraction. A new nonlinear approach is used to characterize performances of this collinear LiNbO3 acousto-optical filter exploiting our revealed specific acousto-optical nonlinearity. We have carried out the experiments with the collinear filter based on the congruent LiNbO3 crystal of 6.3 cm length at λ = 405 and 440 nm to verify our analysis and estimations. We also explore an opportunity to trade an amount of the efficiency to improve the spectral resolution. The transmission efficiency steeply increases with increasing light wavelength and with decreasing length of the filter, nevertheless the efficiency still remains higher than 30% in the near ultraviolet, if the spectral resolution is limited by δλ = 0.28–0.29 A. Moreover, we demonstrate the possibility to reach a resolution as high as δλ = 0.12–0.15 A (R > 24600), preserving at the same time an efficiency higher than 10% over the spectral interval that we considered. It looks like our filter holds the best to our knowledge experimentally confirmed spectral resolution for any collinear acousto-optical spectrometers dedicated to space/airborne operations.

The absorption spectrum of monodeuterated water, HDO has been investigated between 11200 and 12400 cm-1. The spectrum has been recorded using IFS-125M interferometer with spectral resolution of 0.05 cm-1. For measurements White’s-type cell were used. The bright light emitting diode (LED) EDEI-1LS3-R was applied as a source of radiation. Signal to noise ratio was about 104. The spectral line parameters - line positions, intensities and half-widths were obtained by least square fitting. As a result of the spectrum analysis the line list containing more than 1500 lines was created. The spectral line parameters have been compared with the previous measured and calculated data. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

We have demonstrated remarkable enhancement of longitudinal and transverse magneto-optical Kerr effects in magnetoplasmonic crystals based on thin nanostructured films of nickel and iron due to resonant excitation of magnetoplasmonic waves in Faraday and Voight configurations . Manifestations of ultrafast time-dependent transverse magneto-optical Kerr effect are experimentally demonstrated in femtosecond laser pulses reflected from a one-dimensional magnetoplasmonic crystal. We show that exciting surface plasmon-polaritons with magnetization-dependent dispersion law allows one to control the shape of the refected pulse.

This investigation represents a deep and advanced analysis of exploiting lithium niobate (LiNbO3) crystals for the collinear acousto-optical tunable filter (AOTF) in violet and near ultraviolet ranges. The selection of this material is motivated by its high birefringence, which is a key parameter for improving the resolution of AOTF. For this matter, we take into account all the important factors that can deteriorate the resolution in order to find extreme conditions for the best performances. In concrete, we analyze the well- known photorefraction effect accompanied by the light induced absorption in those ranges for the LiNbO3 crystals doped by selected materials. The best observed results have been obtained with magnesium (Mg) dopant in the congruent melt of LiNbO3, which also shifts the absorption edge far into the middle UV-range. This analysis had made it possible to formulate the physical criterion determining the enlarged practical limitations of the incident light power density. Together with previously studied non-uniformity and dispersion of the birefringence along the length of acousto-optical interaction in a crystal, we exploit the recently discovered and experimentally confirmed acousto-optical nonlinearity, which can improve the transmission function inherent in the collinear interaction via applying the acoustic waves of finite amplitude in the AOTF. As a result, the obtained spectral resolution is the best available for any collinear AOTF to our knowledge.

We investigate the components of dissipative multi-wave solitons in the form of three-wave weakly coupled states originating within the collinear acousto-optical interaction due to acoustic waves of finite amplitude. This investigation is carried out in a square-law nonlinear birefringent medium with linear optical losses, theoretically and experimentally. Theoretically, we study the three-wave collinear acousto-optical interaction using several acoustic pulse profiles, with the cases of infinite support (when the acoustic pulse envelope is gradually vanishing on the boundaries) and compact support (when acoustic pulse envelope is cut down on the boundaries), and consider the appropriate boundary conditions in a quasi-stationary regime with the phase mismatch. As a theoretical result, one has found that the system can be described; in particular, by the cnoidal Jacobi elliptic functions whose limiting cases lead to hyperbolic and trigonometric solutions. The experiments dedicated to examine these theoretical results have been done with a X-ray irradiated α-quartz crystalline cell enabling the collinear acousto-optical interaction. The cell used the pure longitudinal acoustic wave with the frequency mismatch along the 6 cm interaction length. Two types of acoustic pulses had been generated, namely, hyperbolic-secant pulse (infinite support) and a bounded rectangular pulse (compact support). During these experiments one had observed the optical components peculiar to the mismatched weakly coupled states. Rather well agreement between the theoretical model, simulated numerically, and the obtained data of measurements for the frequency detuning, acoustic power density, and efficiency of the coupled states localization have been achieved.

In this paper we present the results of Н2 16О absorption spectrum investigation recorded by a high resolution Fouriertransform spectrometer IFS-125M in the region 15500 – 16000 cm-1. Absorption path of 34.8 m and resolution of 0.03 см-1 were chosen to record the spectrum. White type multipass absorption cell with a basic length of 60 cm were used. Light-emitting diode (LED) was applied as a source of radiation. Signal-to-noise ratio is about 104, making it possible to measure parameters of lines with intensity up to 2*10-27 cm/molecule. Least-square-fitting algorithm was used to retrieve of the spectroscopic parameters from measured spectral data set. Spectral line positions and line intensities derived from the fitting were compared to data obtained in previous works.

We present a novel all optical technology for precision nanoscale pattern inspection. The approach utilizes imaging system with the high value of axial chromatic aberration and a low-cost light source tunable in the ~30 nm wavelength bandwidth. Such combination allows us to capture defocused images in highly stable conditions without mechanical scanning of either tested sample or image sensor. Further processing of the diffraction images in the defocused planes gives one an ability to compare inspected objects and, using a library of preliminary measured data, define their geometrical parameters with nanoscale accuracy. The proposed method was tested with calibrated lines (height 50 nm, length 100 μm, width range 40-150 nm with 10 nm step) on top of monocrystalline silicon substrate. Measurement accuracy of the optical technology was estimated as ~1 nm.