Showing papers on "Brillouin scattering published in 2017"

Compact Brillouin devices through hybrid integration on silicon

Abstract: A range of unique capabilities in optical and microwave signal processing and generation have been demonstrated using stimulated Brillouin scattering (SBS). The need to harness SBS in mass-manufacturable integrated circuits has led to a focus on silicon-based material platforms. Remarkable progress in silicon-based Brillouin waveguides has been made, but results have been hindered by nonlinear losses present at telecommunications wavelengths. Here, we report on a new approach to surpass this issue through the integration of a high Brillouin gain material, As2S3, onto a silicon-based chip. We fabricated a compact spiral device within a silicon circuit, achieving an order-of-magnitude improvement in Brillouin amplification. To establish the flexibility of this approach, we fabricated a ring resonator with free spectral range precisely matched to the Brillouin shift, enabling the first demonstration, to our knowledge, of Brillouin lasing in a planar integrated circuit. Combining active photonic components with the SBS devices shown here will enable the creation of compact, mass-manufacturable optical circuits with enhanced functionalities.

On-chip inter-modal Brillouin scattering.

Abstract: Brillouin nonlinearities-which result from coupling between photons and acoustic phonons-are exceedingly weak in conventional nanophotonic silicon waveguides. Only recently have Brillouin interactions been transformed into the strongest and most tailorable nonlinear interactions in silicon using a new class of optomechanical waveguides that control both light and sound. In this paper, we use a multi-mode optomechanical waveguide to create stimulated Brillouin scattering between light-fields guided in distinct spatial modes of an integrated waveguide for the first time. This interaction, termed stimulated inter-modal Brillouin scattering, decouples Stokes and anti-Stokes processes to enable single-sideband amplification and dynamics that permit near-unity power conversion. Using integrated mode multiplexers to address separate optical modes, we show that circulators and narrowband filters are not necessary to separate pump and signal waves. We also demonstrate net optical amplification and Brillouin energy transfer as the basis for flexible on-chip light sources, amplifiers, nonreciprocal devices and signal-processing technologies.

A chip-integrated coherent photonic-phononic memory

Abstract: Controlling and manipulating quanta of coherent acoustic vibrations—phonons—in integrated circuits has recently drawn a lot of attention, since phonons can function as unique links between radiofrequency and optical signals, allow access to quantum regimes and offer advanced signal processing capabilities. Recent approaches based on optomechanical resonators have achieved impressive quality factors allowing for storage of optical signals. However, so far these techniques have been limited in bandwidth and are incompatible with multi-wavelength operation. In this work, we experimentally demonstrate a coherent buffer in an integrated planar optical waveguide by transferring the optical information coherently to an acoustic hypersound wave. Optical information is extracted using the reverse process. These hypersound phonons have similar wavelengths as the optical photons but travel at five orders of magnitude lower velocity. We demonstrate the storage of phase and amplitude of optical information with gigahertz bandwidth and show operation at separate wavelengths with negligible cross-talk. Optical storage implementations based on optomechanical resonator are limited to one wavelength. Here, exploiting stimulated Brillouin scattering, the authors demonstrate a coherent optical memory based on a planar integrated waveguide, which can operate at different wavelengths without cross-talk.

Integrated Waveguide Brillouin Laser

Abstract: The demand for high-performance chip-scale lasers has driven rapid growth in integrated photonics. The creation of such low-noise laser sources is critical for emerging on-chip applications, ranging from coherent optical communications, photonic microwave oscillators remote sensing and optical rotational sensors. While Brillouin lasers are a promising solution to these challenges, new strategies are needed to create robust, compact, low power and low cost Brillouin laser technologies through wafer-scale integration. To date, chip-scale Brillouin lasers have remained elusive due to the difficulties in realization of these lasers on a commercial integration platform. In this paper, we demonstrate, for the first time, monolithically integrated Brillouin lasers using a wafer-scale process based on an ultra-low loss Si3N4/SiO2 waveguide platform. Cascading of stimulated Brillouin lasing to 10 Stokes orders was observed in an integrated bus-coupled resonator with a loaded Q factor exceeding 28 million. We experimentally quantify the laser performance, including threshold, slope efficiency and cascading dynamics, and compare the results with theory. The large mode volume integrated resonator and gain medium supports a TE-only resonance and unique 2.72 GHz free spectral range, essential for high performance integrated Brillouin lasing. The laser is based on a non-acoustic guiding design that supplies a broad Brillouin gain bandwidth. Characteristics for high performance lasing are demonstrated due to large intra-cavity optical power and low lasing threshold power. Consistent laser performance is reported for multiple chips across multiple wafers. This design lends itself to wafer-scale integration of practical high-yield, highly coherent Brillouin lasers on a chip.

Slope-assisted BOTDA based on vector SBS and frequency-agile technique for wide-strain-range dynamic measurements

Abstract: We present a slope-assisted BOTDA system based on the vector stimulated Brillouin scattering (SBS) and frequency-agile technique (FAT) for the wide-strain-range dynamic measurement. A dimensionless coefficient K defined as the ratio of Brillouin phase-shift to gain is employed to demodulate the strain of the fiber, and it is immune to the power fluctuation of pump pulse and has a linear relation of the frequency detuning for the continuous pump and Stokes waves. For a 30ns-square pump pulse, the available frequency span of the K spectrum can reach up to 200MHz, which is larger than fourfold of 48MHz-linewidth of Brillouin gain spectrum. For a single-slope assisted BOTDA, dynamic strain measurement with the maximum strain of 2467.4μe and the vibration frequency components of 10.44Hz and 20.94Hz is obtained. For a multi-slope-assisted BOTDA, dynamic measurement with the strain variation up to 5372.9μe and the vibration frequency components of 5.58Hz and 11.14Hz is achieved by using FAT to extend the strain range.

414 W near-diffraction-limited all-fiberized single-frequency polarization-maintained fiber amplifier.

Abstract: A high-power 1064 nm single-frequency polarization-maintained fiber amplifier based on an all-fiber master oscillator power amplifier configuration is demonstrated. To mitigate the stimulated Brillouin scattering (SBS) and the mode instability (MI) effect, a polarization-maintained Yb-doped fiber with a high dopant concentration and a 25 μm core diameter is adopted in the main amplifier stage; in addition, step-distributed longitudinal strain is imposed on the active fiber to broaden its effective SBS gain spectrum and further increase the SBS threshold. As a result, a pump-limited 414 W single-frequency fiber laser is obtained without signs of SBS and MI. Experimental results show that the SBS threshold is increased by at least two times. The slope efficiency of the main amplifier is about 80%. The polarization degree is higher than 98% at all the power levels. The beam quality is measured with a M2 of 1.34. To the best of our knowledge, this is the highest output power of single-frequency polarization-maintained fiber amplifier based on an all-fiber structure.

Temperature-strain discrimination in distributed optical fiber sensing using phase-sensitive optical time-domain reflectometry.

Abstract: A method based on coherent Rayleigh scattering distinctly evaluating temperature and strain is proposed and experimentally demonstrated for distributed optical fiber sensing. Combining conventional phase-sensitive optical time-domain domain reflectometry (ϕOTDR) and ϕOTDR-based birefringence measurements, independent distributed temperature and strain profiles are obtained along a polarization-maintaining fiber. A theoretical analysis, supported by experimental data, indicates that the proposed system for temperature-strain discrimination is intrinsically better conditioned than an equivalent existing approach that combines classical Brillouin sensing with Brillouin dynamic gratings. This is due to the higher sensitivity of coherent Rayleigh scatting compared to Brillouin scattering, thus offering better performance and lower temperature-strain uncertainties in the discrimination. Compared to the Brillouin-based approach, the ϕOTDR-based system here proposed requires access to only one fiber-end, and a much simpler experimental layout. Experimental results validate the full discrimination of temperature and strain along a 100 m-long elliptical-core polarization-maintaining fiber with measurement uncertainties of ~40 mK and ~0.5 μe, respectively. These values agree very well with the theoretically expected measurand resolutions.

Impulsive Brillouin microscopy

Abstract: Brillouin scattering has been emerging as a viable tool for microscopy. However, most of the work done has been with the use of spontaneous Brillouin scattering, which has several hindrances to its use. In this work, we propose and demonstrate nonlinear Brillouin scattering as a solution to many of these hindrances. Here we demonstrate fast two-dimensional microscopic optical imaging of materials’ mechanical properties for the very first time (to our knowledge) using nonlinear Brillouin scattering. Impulsive stimulated Brillouin scattering (ISBS) was used in an optical configuration that is capable of providing accurate local assessment of viscoelastic properties faster than conventional Brillouin spectroscopy. This proof-of-principle imaging experiment has been demonstrated for materials of known properties and microfluidic devices. Applications to noninvasive biomedical imaging are discussed. The fast acquisition times and strong signal of ISBS coupled with the ability of Brillouin scattering to easily measure materials’ viscoelastic properties make this an attractive technique for biological use.

Wideband tunable optoelectronic oscillator based on the deamplification of stimulated Brillouin scattering.

Abstract: A wideband tunable optoelectronic oscillator (OEO) based on the deamplification of stimulated Brillouin scattering (SBS) is proposed and experimentally demonstrated. A tunable single passband microwave photonic filter (MPF) utilizing phase modulation and SBS deamplification is used to realize the tunability of the OEO. Theoretical analysis of the MPF and phase noise performance of the OEO are presented. The frequency response of the MPF is determined by the + 1st sideband attenuation due to SBS deamplification and phase shift difference between the two sidebands due to chromatic dispersion and SBS. The close-in (< 1 MHz) phase noise of the proposed OEO is shown to be dominated by the laser frequency noise via phase shift of SBS. The conversion of the laser frequency noise to the close-in phase noise of the proposed OEO is effectively reduced compared with the OEO based on amplification by SBS. Tunable 7 to 40 GHz signals are experimentally obtained. The single-sideband (SSB) phase noise at 10 kHz offset is −128 dBc/Hz for 10.30 GHz signal. Compared with the OEO based on SBS amplification, the proposed OEO can achieve a phase noise performance improvement beyond 20 dB at 10 kHz offset. The maximum frequency and power drifts at 10.69 GHz are within 1 ppm and 1.4 dB during 1000 seconds, respectively. To achieve better close-in phase noise performance, lower frequency noise laser and higher pump power are preferred. The experimental results agree well with the theoretical models.

Brillouin spectroscopy of optical microfibers and nanofibers

Abstract: Optical microfibers and nanofibers are currently being widely used in a vast number of applications ranging from quantum and ultra-cold atom optics to optical sensing. However, most existing methods for characterizing these tiny photonic wires are either destructive or rather complex to implement. Here, we describe a new easy-to-implement technique that allows for a complete experimental characterization of subwavelength-diameter tapered optical fibers, including both the uniform and transition sections. Our method is based on a direct and fast numerical analysis of the backward Brillouin scattering spectrum measured using highly sensitive heterodyne coherent detection. It can be performed in situ without any manipulation or optical alignment of optical nanofibers. Sensitivity as high as a few nanometers for fiber diameters ranging from 500 nm to 1.2 μm is reported. This new technique may also help with the design and characterization of micro- and nanoscale photonic chips.

Experimental study on depolarized GAWBS spectrum for optomechanical sensing of liquids outside standard fibers.

Abstract: We report an experimental study on the spectral dependence of depolarized guided acoustic-wave Brillouin scattering (GAWBS) in a silica single-mode fiber (SMF) on acoustic impedance of external materials. The GAWBS spectrum was measured when the acoustic impedance was changed from 1.51 to 2.00 kg/s·mm2. With increasing acoustic impedance, the linewidth increased; the dependence was almost linear with an acoustic impedance dependence coefficient of 0.16 MHz/kg/s·mm2. Meanwhile, with increasing acoustic impedance, the central frequency linearly decreased with an acoustic impedance dependence coefficient of −0.07 MHz/kg/s·mm2. These characteristics are potentially applicable to acoustic impedance sensing.

Integrated continuous-wave aluminum nitride Raman laser

Abstract: Wurtzite aluminum nitride (AlN) is known to exhibit six Raman-active optic phonons, making it appealing for Raman lasing. Here, we demonstrate continuous-wave Raman lasers with a low threshold and a high slope efficiency in high quality factor AlN-on-sapphire microrings. Stokes radiations around 1.7–1.8 μm and cascaded operation into 1.9–2.0 μm are identified with a telecom pump. Two types of Stokes lights with distinct Raman shifts and polarizations are recorded via selective excitation of corresponding optic phonons, in accordance with the Raman selection rules in AlN. The observed lasing behavior is satisfactorily accounted for by a theoretical analysis. Our results indicate that AlN-on-sapphire should be promising for integrated nonlinear optics.

High-resolution, on-chip RF photonic signal processor using Brillouin gain shaping and RF interference.

Abstract: Integrated microwave photonics has strongly emerged as a next-generation technology to address limitations of conventional RF electronics for wireless communications. High-resolution RF signal processing still remains a challenge due to limitations in technology that offer sub-GHz spectral resolution, in particular at high carrier frequencies. In this paper, we present an on-chip high-resolution RF signal processor, capable of providing high-suppression spectral filtering, large phase shifts and ns-scale time delays. This was achieved through tailoring of the Brillouin gain profiles using Stokes and anti-Stokes resonances combined with RF interferometry on a low-loss photonic chip with strong opto-acoustic interactions. Using an optical power of <40 mW, reconfigurable filters with a bandwidth of ~20 MHz and an extinction ratio in excess of 30 dB are synthesized. Through the concept of vector addition of RF signals we demonstrate, almost an order of magnitude amplification in the phase and delay compared to devices purely based upon the slow-light effect of Brillouin scattering. This concept allows for versatile and power-efficient manipulation of the amplitude and phase of RF signals on a photonic chip for applications in wireless communications including software defined radios and beam forming.

Perspectives on stimulated Brillouin scattering

Abstract: This collection of papers describes research that goes into detail on some of the more important issues in the physics of stimulated Brillouin scattering. This perspective describes the earliest years of the physics of stimulated Brillouin scattering, along with key developments that have led to this technically and physically rich field of today's nonlinear optics. Stimulated Brillouin has a profound effect in optical fiber communications, initially discovered by its limit on the transmitted power. By controlling SBS in fibers and making use of its phase conjugation properties in both fibers and bulk media, a wide range of applications have been enabled. Today ring Brillouin lasers in fibers, whispering gallery modes and in photonic integrated circuits provide optical delay lines and switches, pulse shapers and components for increasingly complex and important optical systems.

Chip-based Brillouin radio frequency photonic phase shifter and wideband time delay.

Abstract: We report a chip-based true-time-delay unit based on stimulated Brillouin scattering that uses an on-off Brillouin gain of 52 dB to enable 4 ns delay over a bandwidth of 100 MHz and a phase shift of ∼200°. To verify these operations, we use a two-tap microwave filter configuration and observed changes in the free spectral range of the filter and shift in the spectrum of the filter. The realization of these functionalities on chip-scale devices is critical for phased-array antennas, multibeam satellites, delay lines, arbitrary waveform generation, and reconfigurable microwave photonic filters.

Modal instability induced by stimulated Raman scattering in high-power Yb-doped fiber amplifiers.

Abstract: Modal instability (MI) and stimulated Raman scattering (SRS) are the main obstacles in the power scaling of fiber lasers and amplifiers. In the power scaling of a high-power ytterbium (Yb)-doped master oscillator power amplifier system, a new type of MI has occurred. Experimentally, it is shown that just at the onset of the SRS effect, MI takes place, and the degradation of the beam quality is observed. By the spectra and beam quality measurements, it is revealed that this type of MI can be mitigated firmly by suppressing the SRS effect in high-power Yb-doped fiber amplifiers.

Broadband instantaneous frequency measurement based on stimulated Brillouin scattering.

Abstract: A technique for the instantaneous frequency measurement (IFM) of broadband signals is proposed based on stimulated Brillouin scattering (SBS) in a single-mode optical fiber. The instantaneous frequency and amplitude information is obtained by the narrowband filtering of the acoustic-optic interaction in the SBS process. Through sideband management of the optical-modulation, the IFM bandwidth can be far beyond the Brillouin frequency shift (i.e. ~11 GHz in 1550 nm). Proof-of-concept experiments for both the linearly frequency modulated pulse and frequency Costas coded pulse are carried out to verify the feasibility of the IFM.

Brillouin light scattering studies of 2D magnonic crystals

Abstract: Magnonic crystals, materials with periodic modulation of their magnetic properties, represent the magnetic counterpart of photonic, phononic and plasmonic crystals, and have been largely investigated in recent years because of the possibility of using spin waves as a new means for carrying and processing information over a very large frequency bandwidth. Here, we review recent Brillouin light scattering studies of 2D magnonic crystals consisting of single- and bi-component arrays of interacting magnetic dots or antidot lattices. In particular, we discuss the principal properties of the magnonic band diagram of such systems, with emphasis given to its dependence on both magnetic and the geometrical parameters. Thanks to the possibility of tailoring their band structure by means of several degrees of freedom, planar magnonic crystals offer a good opportunity to design an innovative class of nanoscale microwave devices.

Cascaded forward Brillouin scattering to all Stokes orders

Abstract: Inelastic scattering processes such as Brillouin scattering can often function in cascaded regimes and this is likely to occur in certain integrated opto-acoustic devices. We develop a Hamiltonian formalism for cascaded Brillouin scattering valid for both quantum and classical regimes. By regarding Brillouin scattering as the interaction of a single acoustic envelope and a single optical envelope that covers all Stokes and anti-Stokes orders, we obtain a compact model that is well suited for numerical implementation, extension to include other optical nonlinearities or short pulses, and application in the quantum-optics domain. We then theoretically analyze intra-mode forward Brillouin scattering (FBS) for arbitrary waveguides with and without optical dispersion. In the absence of optical dispersion, we find an exact analytical solution. With a perturbative approach, we furthermore solve the case of weak optical dispersion. Our work leads to several key results on intra-mode FBS. For negligible dispersion, we show that cascaded intra-mode FBS results in a pure phase modulation and discuss how this necessitates specific experimental methods for the observation of fiber-based and integrated FBS. Further, we discuss how the descriptions that have been established in these two classes of waveguides connect to each other and to the broader context of cavity opto-mechanics and Raman scattering. Finally, we draw an unexpected striking similarity between FBS and discrete diffraction phenomena in waveguide arrays, which makes FBS an interesting candidate for future research in quantum-optics.

Brillouin scattering-like effect and non-reciprocal propagation of elastic waves due to spatio-temporal modulation of electrical boundary conditions in piezoelectric media

Abstract: The properties of a one-dimensional phononic crystal made of identical piezoelectric elements separated by thin metallic electrodes connected to the ground are studied theoretically for cases where the locations of the electrical connections change as a function of time with a specific speed. This spatio-temporal modulation of the electrical boundary conditions results in significant non-linear effects that are evidenced numerically. The interaction between an incident harmonic longitudinal wave and the time-dependent phononic crystal is shown to lead to frequency splitting analogous to Brillouin scattering. Moreover, the boundaries of the Bragg bandgaps are strongly affected, and for some specific modulation speed, one-way wave propagation can be achieved.

High-efficiency Brillouin random fiber laser using all-polarization maintaining ring cavity.

Abstract: We report a high-efficiency (25%) Brillouin random fiber laser (BRFL) with Brillouin gain medium of 2-km polarization maintaining fiber (PMF) as well as distributed Rayleigh scattering feedback from 500-m PMF. The characteristics of lasing efficiency and relative intensity noise (RIN) have been comprehensively studied comparing with the BRFLs with half-open ring cavity and bidirectional pumping linear open configuration. The enhanced lasing efficiency using PMF-BRFL with half-open ring cavity enables sub-kHz linewidth, lower phase fluctuation and frequency jitter comparing with phase locked pump laser, thanks to the polarization-matched efficient Brillouin gain in PMFs. The RIN and frequency instability of the proposed PMF-BRFL induced from external disturbance, e.g., mechanical and thermal noise, have been effectively suppressed with respect to conventional SMF-based BRFL.

Resolving 1 million sensing points in an optimized differential time-domain Brillouin sensor.

Abstract: A differential pulse-width pair (DPP) Brillouin distributed fiber sensor is implemented to achieve centimetric spatial resolution over distances of several kilometers. The presented scheme uses a scanning method in which the spectral separation between the two probe sidebands is kept constant, while the optical frequency of the pump is swept to scan the Brillouin spectral response. Experimental results show that this method avoids detrimental temporal distortions of the pump pulses, which in a standard implementation prevent the DPP method from operating over mid-to-long distances. Such a novel scanning procedure allows the resolving, for the first time in pure time-domain Brillouin sensors, of 1,000,000 sensing points, i.e., 1 cm spatial resolution over 10 km in a conventional acquisition time.

Integration of spectral coronagraphy within VIPA-based spectrometers for high extinction Brillouin imaging.

Abstract: VIPA (virtually imaged phase array) spectrometers have enabled rapid Brillouin spectrum measurements and current designs of multi-stage VIPA spectrometers offer enough spectral extinction to probe transparent tissue, cells and biomaterials. However, in highly scattering media or in the presence of strong back-reflections, such as at interfaces between materials of different refractive indices, VIPA-based Brillouin spectral measurements are limited. While several approaches to address this issue have recently been pursued, important challenges remain. Here we have adapted the design of coronagraphs used for exosolar planet imaging to the spectral domain and integrated it in a double-stage VIPA spectrometer. We demonstrate that this yields an increase in extinction up to 20 dB, with nearly no added insertion loss. The power of this improvement is vividly demonstrated by Brillouin imaging close to reflecting interfaces without index matching or sample tilting.

Support vector machine assisted BOTDA utilizing combined Brillouin gain and phase information for enhanced sensing accuracy

Abstract: Benefiting from both Brillouin amplitude and phase spectral responses during Brillouin scattering, a support vector machine (SVM) assisted Brillouin optical time domain analyzer (BOTDA) enabling the improvement of sensing accuracy with only a slight sacrifice of processing speed has been proposed and demonstrated. Only one SVM model, i.e. SVM-(g + p), is required to effectively combine the Brillouin gain and phase information in the training and testing phases, which avoids separate Brillouin gain spectrum (BGS) and Brillouin phase spectrum (BPS) fitting, and hence saves the processing time. Both simulation and experiments using different parameters were conducted to evaluate the improved performance of SVM-(g + p). Compared with the case of using BGS only or BPS only, SVM assisted BOTDA using combined BGS and BPS enhances the accuracy of temperature extraction by about 30% over a wide range of simulation and experiment parameters, only at a slight expense of the processing speed. Although the processing of both gain and phase information takes extra time, SVM-(g + p) assisted BOTDA still has a processing speed 80 times faster than that of using a conventional curve fitting method like Lorentzian curve fitting (LCF). The improved accuracy, together with fast processing speed, is crucial for future high-speed and accurate BOTDA sensors based on both Brillouin gain and phase detection.

On-chip Brillouin purification for frequency comb-based coherent optical communications.

Abstract: In this Letter, for the first time, to the best of our knowledge, we harness on-chip Brillouin scattering for narrowband amplification and spectral purification of frequency comb lines for coherent optical communications. A parametrically generated optical frequency comb with a low carrier-to-noise power ratio was filtered through narrowband Brillouin amplification utilizing the same comb as the optical pump. This was achieved on a photonic chip to enable successful transmission of an advanced modulation format signal: 64-level quadrature amplitude modulation. 96 Gb/s data were modulated on two polarizations on multiple comb lines across 1532.9-1557.5 nm, demonstrating the scalability of this concept for operation in wavelength division multiplexing applications. The small form factor of the photonic chip reduces the polarization drifts when compared to optical fibers and paves the way for photonic integration.

Applications of Brillouin Dynamic Grating to Distributed Fiber Sensors

Abstract: In the process of stimulated Brillouin scattering (SBS), acoustic waves are generated by the interference of counterpropagating optical waves via electrostriction effect. These acoustic waves not only stimulate the Brillouin scattering process, but can also play a role of moving Bragg reflector for another optical wave when a proper phase-matching condition is satisfied between the interacting optical waves. Brillouin dynamic grating (BDG) represents this secondary role of the acoustic wave, which shows a unique reflection spectrum, called BDG spectrum. The BDG spectrum generally shows higher sensitivity to the change of physical variables, such as temperature and strain than ordinary Brillouin gain spectrum (BGS), and also provides information on the waveguide parameters, such as polarization or modal birefringence with high accuracy. This paper reviews the operation principle of BDG under various conditions and the research progresses on its application to distributed fiber sensors.

High-energy sub-phonon lifetime pulse compression by stimulated Brillouin scattering in liquids.

Abstract: Multi-Joule level stimulated Brillouin scattering (SBS) pulse compression below the acoustic phonon lifetime is demonstrated with a energy-scalable generator-amplifier setup Single-pass compression of pulses longer than 20τB (τB as phonon lifetime) to as short as 05τB with ~100 mJ pulse energy is realized from the generator, by choosing the focusing length to match approximately with the full length at half maximum of the input Gaussian pulses The interaction length is identified, both experimentally and numerically, as the key parameter in achieving sub-phonon lifetime pulse compression, with its main mechanism being the steepening of the Stokes pulse trailing edge via energy exchange process After combining the generator with an amplifier that involves only collimated beams and serves as energy booster, the compression of 9 ns, 2 J pulses at 532 nm into 170 ps, 13 J per pulse is achieved in water, with very good stability in both pulse energy and duration This work demonstrates for the first time the efficient high-energy SBS sub-phonon lifetime pulse compression, and paves a way to the reliable generation of sub-200 ps laser pulses with Joule-level energy

X-ray amplification by stimulated Brillouin scattering.

Abstract: Plasma-based parametric amplification using stimulated Brillouin scattering offers a route to coherent x-ray pulses orders of magnitude more intense than those of the brightest available sources. Brillouin amplification permits amplification of shorter wavelengths with lower pump intensities than Raman amplification, which Landau and collisional damping limit in the x-ray regime. Analytic predictions, numerical solutions of the three-wave-coupling equations, and particle-in-cell simulations suggest that Brillouin amplification in solid-density plasmas will allow compression of current x-ray free-electron laser pulses to subfemtosecond durations and unprecedented intensities.

Experimental Analysis of Steel Beams Subjected to Fire Enhanced by Brillouin Scattering-Based Fiber Optic Sensor Data

Abstract: This paper presents high temperature measurements using a Brillouin scattering-based fiber optic sensor and the application of the measured temperatures and building code recommended material parameters into enhanced thermomechanical analysis of simply supported steel beams subjected to combined thermal and mechanical loading. The distributed temperature sensor captures detailed, nonuniform temperature distributions that are compared locally with thermocouple measurements with less than 4.7% average difference at 95% confidence level. The simulated strains and deflections are validated using measurements from a second distributed fiber optic (strain) sensor and two linear potentiometers, respectively. The results demonstrate that the temperature-dependent material properties specified in the four investigated building codes lead to strain predictions with less than 13% average error at 95% confidence level and that the Europe building code provided the best predictions. However, the implicit consi...

Single-shot distributed Brillouin optical time domain analyzer.

Abstract: We demonstrate a novel single-shot distributed Brillouin optical time domain analyzer (SS-BOTDA). In our method, dual-polarization probe with orthogonal frequency-division multiplexing (OFDM) modulation is used to acquire the distributed Brillouin gain spectra, and coherent detection is used to enhance the signal-to-noise ratio (SNR) drastically. Distributed temperature sensing is demonstrated over a 1.08 km standard single-mode fiber (SSMF) with 20.48 m spatial resolution and 0.59 °C temperature accuracy. Neither frequency scanning, nor polarization scrambling, nor averaging is required in our scheme. All the data are obtained through only one-shot measurement, indicating that the sensing speed is only limited by the length of fiber.