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Showing papers on "Brillouin scattering published in 2018"


Journal ArticleDOI
08 Jun 2018-Science
TL;DR: It is shown that this silicon-based Brillouin laser enters a regime of dynamics in which optical self-oscillation produces phonon linewidth narrowing, which provides a platform to develop a range of applications for monolithic integration within silicon photonic circuits.
Abstract: Brillouin laser oscillators offer powerful and flexible dynamics as the basis for mode-locked lasers, microwave oscillators, and optical gyroscopes in a variety of optical systems However, Brillouin interactions are markedly weak in conventional silicon photonic waveguides, stifling progress toward silicon-based Brillouin lasers The recent advent of hybrid photonic-phononic waveguides has revealed Brillouin interactions to be one of the strongest and most tailorable nonlinearities in silicon In this study, we have harnessed these engineered nonlinearities to demonstrate Brillouin lasing in silicon Moreover, we show that this silicon-based Brillouin laser enters a regime of dynamics in which optical self-oscillation produces phonon linewidth narrowing Our results provide a platform to develop a range of applications for monolithic integration within silicon photonic circuits

184 citations


Journal ArticleDOI
TL;DR: In this paper, a photonic-integrated Brillouin cascaded-order (SBS) laser is proposed to achieve a sub-Hz (0.7 Hz) emission linewidth.
Abstract: Photonic systems and technologies traditionally relegated to table-top experiments are poised to make the leap from the laboratory to real-world applications through integration. Stimulated Brillouin scattering (SBS) lasers, through their unique linewidth narrowing properties, are an ideal candidate to create highly-coherent waveguide integrated sources. In particular, cascaded-order Brillouin lasers show promise for multi-line emission, low-noise microwave generation and other optical comb applications. Photonic integration of these lasers can dramatically improve their stability to environmental and mechanical disturbances, simplify their packaging, and lower cost. While single-order silicon and cascade-order chalcogenide waveguide SBS lasers have been demonstrated, these lasers produce modest emission linewidths of 10-100 kHz. We report the first demonstration of a sub-Hz (~0.7 Hz) fundamental linewidth photonic-integrated Brillouin cascaded-order laser, representing a significant advancement in the state-of-the-art in integrated waveguide SBS lasers. This laser is comprised of a bus-ring resonator fabricated using an ultra-low loss Si3N4 waveguide platform. To achieve a sub-Hz linewidth, we leverage a high-Q, large mode volume, single polarization mode resonator that produces photon generated acoustic waves without phonon guiding. This approach greatly relaxes phase matching conditions between polarization modes, and optical and acoustic modes. Using a theory for cascaded-order Brillouin laser dynamics, we determine the fundamental emission linewidth of the first Stokes order by measuring the beat-note linewidth between and the relative powers of the first and third Stokes orders. Extension to the visible and near-IR wavebands is possible due to the low optical loss from 405 nm to 2350 nm, paving the way to photonic-integrated sub-Hz lasers for visible-light applications.

155 citations


Journal ArticleDOI
TL;DR: In this paper, a non-local acousto-optic light scattering was used to produce non-reciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform.
Abstract: Non-reciprocal light propagation is essential to control optical crosstalk and back-scatter in photonic systems. However, realizing high-fidelity non-reciprocity in low-loss integrated photonic circuits remains challenging. Here, we experimentally demonstrate a form of non-local acousto-optic light scattering to produce non-reciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform. In this system, a travelling-wave acoustic phonon driven by optical forces in a silicon waveguide spatiotemporally modulates light in a separate waveguide through linear interband Brillouin scattering. This process extends narrowband optomechanics-based schemes for non-reciprocity to travelling-wave physics, enabling large operation bandwidths of more than 125 GHz and up to 38 dB of non-reciprocal contrast between forward- and backward-propagating optical waves. The modulator operation wavelength is tunable over a 35-nm range by varying the optical drive wavelength. Such travelling-wave acousto-optic interactions provide a promising path toward the realization of broadband, low-loss isolators and circulators within integrated photonics. Non-reciprocal single-sideband modulation and mode conversion are realized in a low-loss integrated silicon waveguide, enabling >125 GHz operation bandwidths and up to 38 dB of non-reciprocal contrast between forward- and backward-propagating waves.

153 citations


Journal ArticleDOI
TL;DR: A distributed forward Brillouin sensor that is sensitive to quantities outside the fibre bulk is demonstrated that allows real-time sampling at high spatial resolution, but is so far restricted to measuring quantities inside the fibre core.
Abstract: The distributed fibre sensing technology based on backward stimulated Brillouin scattering (BSBS) is experiencing a rapid development. However, all reported implementations of distributed Brillouin fibre sensors until today are restricted to detecting physical parameters inside the fibre core. On the contrary, forward stimulated Brillouin scattering (FSBS), due to its resonating transverse acoustic waves, is being studied recently to facilitate innovative detections in the fibre surroundings, opening sensing domains that are impossible with BSBS. Nevertheless, due to the co-propagating behaviour of the pump and scattered lights, it is a challenge to position-resolve FSBS information along a fibre. Here we show a distributed FSBS analysis based on recovering the FSBS induced phase change of the propagating light waves. A spatial resolution of 15 m is achieved over a length of 730 m and the local acoustic impedances of water and ethanol in a 30 m-long uncoated fibre segment are measured, agreeing well with the standard values.

116 citations


Journal ArticleDOI
TL;DR: Brillouin scattering of photons in the whispering gallery modes by magnons in the magnetostatic modes is experimentally investigated, finding that the conservation of the orbital angular momentum results in different nonreciprocal behavior in the Brillouin light scattering.
Abstract: A ferromagnetic sphere can support optical vortices in the form of whispering gallery modes and magnetic quasivortices in the form of magnetostatic modes with nontrivial spin textures. These vortices can be characterized by their orbital angular momenta. We experimentally investigate Brillouin scattering of photons in the whispering gallery modes by magnons in the magnetostatic modes, zeroing in on the exchange of the orbital angular momenta between the optical vortices and magnetic quasivortices. We find that the conservation of the orbital angular momentum results in different nonreciprocal behavior in the Brillouin light scattering. New avenues for chiral optics and optospintronics can be opened up by taking the orbital angular momenta as a new degree of freedom for cavity optomagnonics.

115 citations


Journal ArticleDOI
TL;DR: In this paper, a traveling-wave acoustic phonon driven via optical forces in a silicon waveguide is used to modulate light in a spatially separate waveguide through a linear inter-band Brillouin scattering process.
Abstract: Achieving nonreciprocal light propagation in photonic circuits is essential to control signal crosstalk and optical back-scatter. However, realizing high-fidelity nonreciprocity in low-loss integrated photonic systems remains challenging. In this paper, we experimentally demonstrate a device concept based on nonlocal acousto-optic light scattering to produce nonreciprocal single-sideband modulation and mode conversion in an integrated silicon photonic platform. In this process, a traveling-wave acoustic phonon driven via optical forces in a silicon waveguide is used to modulate light in a spatially separate waveguide through a linear inter-band Brillouin scattering process. We demonstrate up to 38 dB of nonreciprocity with 37 dB of single-sideband suppression. In contrast to prior Brillouin- and optomechanics-based schemes for nonreciprocity, the bandwidth of this scattering process is set through optical phase-matching, not acoustic or optical resonances. As a result, record-large bandwidths in excess of 125 GHz are realized, with potential for significant further improvement through optical dispersion engineering. Tunability of the nonreciprocal modulator operation wavelength over a 35 nm bandwidth is demonstrated by varying the optical pump wavelength. Such traveling-wave acousto-optic modulators provide a promising path toward the realization of broadband, low-loss isolators and circulators in integrated photonic circuits.

111 citations


Journal ArticleDOI
20 Jan 2018
TL;DR: Soliton microcombs with repetition rates as low as 1.86 GHz are demonstrated in this article, which is a regime more typical of table-top combs and is important in spectroscopy and relax requirements on comb processing electronics.
Abstract: Soliton microcombs with repetition rates as low as 1.86 GHz are demonstrated, thereby entering a regime more typical of table–top combs. Low rates are important in spectroscopy and relax requirements on comb processing electronics.

102 citations


Journal ArticleDOI
Gil Bashan1, Hilel Hagai Diamandi1, Yosef London1, Eyal Preter1, Avi Zadok1 
TL;DR: Distributed optomechanical mapping of outside media, where light cannot reach is introduced: forward stimulated Brillouin scattering through Rayleigh back-scatter is resolved and a new sensor configuration is established: optomeschanical time-domain reflectometry, with several potential applications.
Abstract: Optical fibres constitute an exceptional sensing platform. However, standard fibres present an inherent sensing challenge: they confine light to an inner core. Consequently, distributed fibre sensors are restricted to the measurement of conditions that prevail within the core. This work presents distributed analysis of media outside unmodified, standard fibre. Measurements are based on stimulated scattering by guided acoustic modes, which allow us to listen where we cannot look. The protocol overcomes a major difficulty: guided acoustic waves induce forward scattering, which cannot be mapped using time-of-flight. The solution relies on mapping the Rayleigh backscatter contributions of two optical tones, which are coupled by the acoustic wave. Analysis is demonstrated over 3 km of fibre with 100 m resolution. Measurements distinguish between air, ethanol and water outside the cladding, and between air and water outside polyimide-coated fibres. The results establish a new sensor configuration: optomechanical time-domain reflectometry, with several potential applications. Distributed fibre sensors are so far restricted to the monitoring of conditions within the core. Here, Bashan et al. introduce distributed optomechanical mapping of outside media, where light cannot reach. The sensor resolves forward stimulated Brillouin scattering through Rayleigh back-scatter.

93 citations


Journal ArticleDOI
TL;DR: Time-domain Brillouin scattering is an all-optical experimental technique based on ultrafast lasers applied for generation and detection of coherent acoustic pulses on time durations of picoseconds and length scales of nanometers as mentioned in this paper.
Abstract: Time-domain Brillouin scattering is an all-optical experimental technique based on ultrafast lasers applied for generation and detection of coherent acoustic pulses on time durations of picoseconds and length scales of nanometers. In transparent materials, scattering of the probe laser beam by the coherent phonons permits imaging of sample inhomogeneity. The transient optical reflectivity of the sample recorded by the probe beam as the acoustic nanopulse propagates in space contains information on the acoustical, optical, and acousto-optical parameters of the material under study. The experimental method is based on a heterodyning where weak light pulses scattered by the coherent acoustic phonons interfere at the photodetector with probe light pulses of significantly higher amplitude reflected from various interfaces of the sample. The time-domain Brillouin scattering imaging is based on Brillouin scattering and has the potential to provide all the information that researchers in materials science, physics, chemistry, biology, etc., get with classic frequency-domain Brillouin scattering of light. It can be viewed as a replacement for Brillouin scattering and Brillouin microscopy in all investigations where nanoscale spatial resolution is either required or advantageous. Here, we review applications of time-domain Brillouin scattering for imaging of nanoporous films, ion-implanted semiconductors and dielectrics, texture in polycrystalline materials and inside vegetable and animal cells, and for monitoring the transformation of nanosound caused by nonlinearity and focusing. We also discuss the perspectives and the challenges for the future.

88 citations


Journal ArticleDOI
TL;DR: In this paper, a comprehensive review of the characteristics of different types of SBS materials, SBS applications, experimental design methods, as well as the parameter optimization method is provided, which is expected to provide reference and guidance to SBS related experiments.

79 citations



Journal ArticleDOI
TL;DR: In this paper, a nonlinear optimization of periodic phase modulation for suppression of stimulated Brillouin scattering (SBS) in single-mode optical fibers is proposed, where the authors use nonlinear multiparameter Pareto optimization to find modulations that represent the best tradeoff between SBS and optical linewidth, as measured by its rms value.
Abstract: We theoretically investigate nonlinear optimization of periodic phase modulation for suppression of stimulated Brillouin scattering (SBS) in single-mode optical fibers. We use nonlinear multiparameter Pareto optimization to find modulations that represent the best tradeoff between SBS and optical linewidth, as measured by its rms value. The optimization uses a temporal-amplitude-domain finite-difference Brillouin solver with noise initiation to find the best phase modulation patterns in the presence of coherent so-called cross-interactions. These can be important in short fibers, when the period is large enough to make the frequency-domain separation of the modulated signal comparable to, or smaller than, the Brillouin gain linewidth. We calculate the SBS threshold for the optimized modulation patterns and find that smaller spectral line spacing improves the SBS threshold for the same linewidth. By contrast, whereas the maximum modulation depth and modulation frequency influence the range of accessible linewidths, they do not significantly alter the threshold for a given linewidth. We investigate the dependence on fiber length and find that while shorter fibers have a higher threshold, the increase is smaller than the often-assumed inverse dependence on length. Furthermore, we find that optimized formats are superior in terms of SBS threshold as well as in terms of linewidth control, compared to random modulation.

Journal ArticleDOI
TL;DR: In this paper, an all-fiber narrow-linewidth amplifier employing a bidirectional pump scheme and cascaded white-noise-source phase-modulated seed laser is demonstrated.
Abstract: We demonstrate an all-fiber narrow-linewidth amplifier employing a bidirectional pump scheme and cascaded white-noise-source phase-modulated seed laser. The stimulated Raman scattering effect in the amplifier is investigated by substituting different types of seed lasers. The influence of pump distributions and seed injection power on mode instability (MI) in the amplifier is also experimentally investigated. As a result, a 3 dB linewidth of 0.175 nm and a beam quality of M 2 ≈ 1.5 are obtained at the output of ~3 kW, without observation of MI and stimulated Brillouin scattering effect. With the further increase of pump power, MI occurs as the output exceeds 3.17 kW, along with beam quality degradation. Optical efficiency decreases to 71.5% at the ultimate output of 3.5 kW. Therefore MI becomes the main limitation to further power scaling.

Journal ArticleDOI
TL;DR: In this paper, the authors report the first demonstration of MW Brillouin random fiber laser in the telecom spectral window around 1.5μm based on a unique random fiber grating (RFG).
Abstract: Multi-wavelength (MW) laser sources with high optical signal-to-noise ratios (OSNR) are of great interest for optical communications with ultrahigh data capacity as well as microwave and terahertz photonics. In this paper, we report the first demonstration of MW Brillouin random fiber laser in the telecom spectral window around 1.5 μm based on a unique random fiber grating (RFG). Random feedback by enhanced distributed Rayleigh scattering from the RFG basically enables a high-efficiency random lasing resonance of the Stokes wave via stimulated Brillouin scattering in optical fibers. A subfiber loop eventually delivers the cascading process for the high-efficiency generation of up to a 14-order Stokes’ comb with an ultrahigh OSNR of 41 dB and an optimized peak power discrepancy of 3.4 dB. Thanks to Rayleigh scattered random feedback from the RFG, single longitudinal mode operation of the Stokes laser emission is achieved.

Journal ArticleDOI
TL;DR: A commercially available 80- μm-diameter optical fiber coated with a 8-μm-thick polyimide coating layer is used to measure the acoustic impedances of the surrounding liquids, showing accurate measurement results while retaining the mechanical strength of the fiber.
Abstract: The standard single-mode fiber has been demonstrated as an optomechanical sensor recently to measure the acoustic impedances of surrounding liquids by means of the generation and detection of forward-stimulated Brillouin scattering (FSBS). FSBS allows the mechanical properties of an external material to be probed directly through the interaction of guided light and transverse sound waves that occurs entirely inside the fiber structure. In this technique, having a low-loss interface between the fiber bulk and the external medium is essential for precise measurement; however, it leads to the necessary but impractical removal of the thick polymer fiber coating in most reported methods. Here, we use a commercially available 80-μm-diameter optical fiber coated with a 8-μm-thick polyimide coating layer to measure the acoustic impedances of the surrounding liquids, showing accurate measurement results while retaining the mechanical strength of the fiber.


Journal ArticleDOI
TL;DR: In this article, a stable multiwavelength erbium-doped fiber laser (EDFL) based on random distributed feedback (RDFB) is presented, which consists of a half-opened linear cavity in which a mirror forms one end, while the other end is connected to RDFB of a 25-km-long single mode fiber.
Abstract: A stable multiwavelength erbium-doped fiber laser (EDFL) based on random distributed feedback (RDFB) is presented. The random EDFL consists of a half-opened linear cavity in which a mirror forms one end, while the other end is connected to RDFB of a 25-km-long single mode fiber. In the laser cavity, the instability caused by the RDFB and cascaded stimulated Brillouin scattering is successfully mitigated by four wave mixing effect in a 2-km-long highly nonlinear fiber. Experimental results indicate the generation of 24 stable laser lines at the pump power of 350 mW. The recorded peak power fluctuation for the laser is less than 0.7 dB in a 60-min duration, illustrating the stability of the multiwavelength random fiber laser.

Journal ArticleDOI
TL;DR: A power-efficient scheme based on the concept of phase amplification to improve Brillouin-based phase processing capability is introduced, with a focus on applications requiring phase control of RF signals, including phase shifters, delay lines, and separate carrier tuning.
Abstract: Manipulating radio frequency (RF) signals in integrated photonic devices has recently emerged as a new paradigm for wireless communications, enabling high-frequency signal processing and broadband frequency agility in miniaturized photonic platforms. These advances are crucial for space and airborne applications which are weight and size sensitive. Recent progress in on-chip stimulated Brillouin scattering (SBS) using high gain has shown great potentials for RF photonic signal processing, owing to its inherent advantages of high resolution, high reconfigurability, and flexible programmability. On-chip SBS serves as a versatile and high-performance toolbox to process and manipulate the amplitude and phase of RF signals in the optical domain. In this paper, we provide a brief overview of recent advances achieved using SBS in planar waveguides, with a focus on applications requiring phase control of RF signals, including phase shifters, delay lines, and separate carrier tuning. We introduce a power-efficient scheme based on the concept of phase amplification to improve Brillouin-based phase processing capability.

Journal ArticleDOI
TL;DR: Stable droplets that cohost equatorial acoustical and optical resonances phase matched are used to enable the exchange of energy and momentum between sound and light to stimulate optomechanical surface waves.
Abstract: Liquid droplets are ubiquitous in nature wherein surface tension shapes them into perfect spheres with atomic-scale smooth surfaces. Here, we use stable droplets that cohost equatorial acoustical and optical resonances phase matched to enable the exchange of energy and momentum between sound and light. Relying on free-space laser excitation of multiple whispering-gallery modes, we harness a triple-resonant forward Brillouin scattering to stimulate optomechanical surface waves. Nonlinear amplification of droplet vibrations in the 60-70 MHz range is realized with spectral narrowing beyond the limit of material loss, thereby activating the droplet as hypersound-laser emitter.

Journal ArticleDOI
TL;DR: A chaotic Brillouin optical correlation-domain analysis system for distributed fiber sensing with utilization of a chaotic laser with a low coherence state ensures high spatial resolution.
Abstract: We propose and experimentally demonstrate a chaotic Brillouin optical correlation-domain analysis system for distributed fiber sensing. The utilization of a chaotic laser with a low coherence state ensures high spatial resolution. The experimental results demonstrate a 4 cm spatial resolution over a 906 m measurement range. The uncertainty in the measurement of the local Brillouin frequency shift is ±1.2 MHz. The analysis of the expected spatial resolution and signal-to-noise ratio is also given.

Journal ArticleDOI
TL;DR: An ultrahigh-speed Brillouin optical correlation domain analysis (BOCDA) with a single-position sampling rate of 200 kS/s and a spatial resolution of 8 cm is proposed and demonstrated and a novel measuring method which moves the correlation peak and sweeps the pump-probe frequency interval simultaneously is proposed.
Abstract: In this paper, we propose and demonstrate an ultrahigh-speed Brillouin optical correlation domain analysis (BOCDA) with a single-position sampling rate of 200 kS/s and a spatial resolution of 8 cm. The Brillouin gain spectrum (BGS) is obtained by using a data subtraction scheme rather than the conventional lock-in amplifier (LIA) detection configuration, thus removing the limitation of measurement speed imposed by the LIA. Meanwhile, a voltage controlled oscillator (VCO) is used to sweep the frequency interval between the pump and the probe rapidly. As a proof of concept, we implement measurements of various dynamic strains with frequencies up to 20 kHz at arbitrary position. Moreover, to implement high-speed distributed measurements of Brillouin frequency shift (BFS) along the whole fiber under test (FUT), we propose a novel measuring method which moves the correlation peak and sweeps the pump-probe frequency interval simultaneously. A repetition rate of 1 kHz is verified by measuring dynamic strains with frequencies up to 200 Hz, for distributed measurements performed with 200 points.

Journal ArticleDOI
TL;DR: A Brillouin optical time-domain analysis method based on a closed-loop control system that acts as a low-pass filter that considerably rejects the noise from photodetector, with an efficiency that fundamentally outperforms basic averaging is proposed.
Abstract: A Brillouin optical time-domain analysis (BOTDA) method based on a closed-loop control system is proposed to track fast variations of the Brillouin frequency shift along the sensing fiber. While the method eliminates the gain spectral scanning, the exact distributed Brillouin frequency profile is retrieved directly from the output of a closed-loop controller with no need of postprocessing. Moreover, as the operating frequency is being continuously updated to follow the Brillouin frequency change, an unlimited temperature or strain measurement range can be achieved. Both theoretical analysis and experimental results validate that the closed-loop-controlled BOTDA acts as a low-pass filter that considerably rejects the noise from photodetector, with an efficiency that fundamentally outperforms basic averaging. By optimizing the closed-loop parameters, the measurement time is reduced from a few minutes to a couple of seconds compared with standard BOTDA, i.e., two orders of magnitude improvement in terms of measurement speed, while keeping the same accuracy and measurement conditions. If the sampling time interval that is limited by our instrument can be further reduced, the method offers the potentiality of km-range sensing with sub-second measurement time, with an unmatched favorable tradeoff between measurand accuracy and closed-loop delay.

Journal ArticleDOI
TL;DR: It is demonstrated that the Lorentzian cross-correlation technique results in the largest BFS offset error due to truncation, while exhibiting the smallest BFS uncertainty and the shortest processing time.
Abstract: The performance of post-processing techniques carried out on the Brillouin gain spectrum to estimate the Brillouin frequency shift (BFS) in standard Brillouin distributed sensors is evaluated. Curve fitting methods with standard functions such as polynomial and Lorentzian, as well as correlation techniques such as Lorentzian Cross-correlation and Cross Reference Plot Analysis (CRPA), are considered for the analysis. The fitting procedures and key parameters for each technique are optimized, and the performance in terms of BFS uncertainty, BFS offset error and processing time is compared by numerical simulations and through controlled experiments. Such a quantitative comparison is performed in varying conditions including signal-to-noise ratio (SNR), frequency measurement step, and BGS truncation. It is demonstrated that the Lorentzian cross-correlation technique results in the largest BFS offset error due to truncation, while exhibiting the smallest BFS uncertainty and the shortest processing time. A novel approach is proposed to compensate such a BFS offset error, which enables the Lorentzian cross-correlation technique to completely outperform other fitting methods.

Journal ArticleDOI
25 Mar 2018-Sensors
TL;DR: A hybrid DOFS system, which can simultaneously measure temperature/strain and vibration over 150 km, is elaborately designed via integrating the Brillouin optical time-domain analyzer (BOTDA) and phase-sensitive opticalTime-domain reflectometry (Ф-OTDR).
Abstract: In the distributed optical fiber sensing (DOFS) domain, simultaneous measurement of vibration and temperature/strain based on Rayleigh scattering and Brillouin scattering in fiber could have wide applications. However, there are certain challenges for the case of ultra-long sensing range, including the interplay of different scattering mechanisms, the interaction of two types of sensing signals, and the competition of pump power. In this paper, a hybrid DOFS system, which can simultaneously measure temperature/strain and vibration over 150 km, is elaborately designed via integrating the Brillouin optical time-domain analyzer (BOTDA) and phase-sensitive optical time-domain reflectometry (Ф-OTDR). Distributed Raman and Brillouin amplifications, frequency division multiplexing (FDM), wavelength division multiplexing (WDM), and time division multiplexing (TDM) are delicately fused to accommodate ultra-long-distance BOTDA and Ф-OTDR. Consequently, the sensing range of the hybrid system is 150.62 km, and the spatial resolution of BOTDA and Ф-OTDR are 9 m and 30 m, respectively. The measurement uncertainty of the BOTDA is ± 0.82 MHz. To the best of our knowledge, this is the first time that such hybrid DOFS is realized with a hundred-kilometer length scale.

Journal ArticleDOI
Elsa Garmire1
TL;DR: Stimulated Brillouin scattering (SBS) is embedded today in a variety of optical systems, such as advanced high-power lasers, sensors, microwave signal processors, scientific instrumentation, and optomechanical systems as discussed by the authors.
Abstract: Stimulated Brillouin scattering (SBS) is embedded today in a variety of optical systems, such as advanced high-power lasers, sensors, microwave signal processors, scientific instrumentation, and optomechanical systems. Reduction in SBS power requirements involves use of optical fibers, integrated optics, micro-optic devices, and now nano-optics, often in high Q cavities. It has taken fifty years from its earliest invention by conceptual discovery until today for SBS to become a practical and useful technology in a variety of applications. Some of these applications are explained and it is shown how they are tied to particular attributes of SBS: phase conjugation, frequency shifts, low noise, narrow linewidth, frequency combs, optical and microwave signal processing, etc.

Journal ArticleDOI
TL;DR: In this article, a tunable dual pump-probe optical source for distributed Brillouin optical time-domain analysis (BOTDA) was proposed, which is capable of a tuning range of ∼200 MHz without using phase-locked loop or optical sideband generation techniques, and exhibits a linewidth smaller than 2.5mm.
Abstract: A theoretical and experimental study has been carried out on a tunable dual pump-probe optical source for distributed Brillouin optical time-domain analysis (BOTDA). The developed source exploits a modified Brillouin ring laser technology and is capable of a tuning range of ∼200 MHz without using phase-locked loop or optical sideband generation techniques, and exhibits a linewidth smaller than 2.5 MHz and ∼0.5 mW power. In BOTDA experiments, the proposed source has demonstrated to be an efficient solution enabling distributed sensing over 10 km single mode fiber with a spatial resolution of ∼4 m, and a strain and temperature resolutions of ∼10 μ ϵ and ∼0.5 °C respectively.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed an additional noise-free, independent center frequency and bandwidth tunable optical filter based on stimulated Brillouin scattering (SBS) losses, which suppressed the out-of-band signal with two broadened symmetric SBS losses.
Abstract: In this paper, we propose an additional noise-free, independent center frequency and bandwidth tunable optical filter based on stimulated Brillouin scattering (SBS) losses. By suppressing the out-of-band signal with two broadened symmetric SBS losses, tunable pass bandwidths from 500 MHz to 9.5 GHz and the independent center frequency tunability are demonstrated. Considering the limited SBS interaction in the center frequency range, a flat-top response with minimum 0.3 dB ripple is achieved. Assisted by the extra suppression from polarization pulling, a maximum selectivity of 20 dB and an ultrahigh 250 dB/GHz roll-off are reached. A gain-based SBS filter adds noise to the filtered signal. However, for our proposed filter setup, no additional noise is detected due to the transparency in the passband. Considering the wide independent bandwidth and center frequency tunability, flat-top response, and low-noise characteristic, our proposed filter can be perfectly used as a supplement of most commercialized conventional tunable optical single bandpass filters, whose minimum bandwidth is limited by 10 GHz.

Journal ArticleDOI
TL;DR: It turns out that the optimal SNR performance depends in inverse proportion on the value of maximum single-pulse Brillouin amplification, which is ultimately determined by the spatial resolution.
Abstract: The performance of unipolar unicolor coded Brillouin optical time-domain analysis (BOTDA) is evaluated based on both Simplex and Golay codes. Four major detrimental factors that limit the system performance, including decoded-gain trace distortion, coding pulse power non-uniformity, polarization pulling and higher-order non-local effects, are thoroughly investigated. Through theoretical analysis and an experimental validations, solutions and optimal design conditions for unipolar unicolor coded BOTDA are clearly established. First, a logarithmic normalization approach is proposed to resolve the linear accumulated Brillouin amplification without distortion. Then it is found out that Simplex codes are more robust to pulse power non-uniformity compared to Golay codes; whilst the use of a polarization scrambler must be preferred in comparison to a polarization switch to mitigate uncompensated fading induced by polarization pulling in the decoded traces. These optimal conditions enables the sensing performance only limited by higher-order non-local effects. To secure systematic errors below 1.3 MHz on the Brillouin frequency estimation, while simultaneously reaching the maximum signal-to-noise ratio (SNR), a mathematical model is established to trade-off the key parameters in the design, i.e., the single-pulse Brillouin amplification, code length and probe power. It turns out that the optimal SNR performance depends in inverse proportion on the value of maximum single-pulse Brillouin amplification, which is ultimately determined by the spatial resolution. The analysis here presented is expected to serve as a quantitative guideline to design a distortion-free coded BOTDA system operating at maximum SNR.

Journal ArticleDOI
TL;DR: This is the first time that an annealed gold-coated fiber has been applied for distributed high-temperature strain sensing, which demonstrates the potential applications for strain monitoring in complex, high-Temperature devices such as jet engines or turbines.
Abstract: In this study, the distributed temperature and strain sensing with an annealed single mode gold-coated optical fiber over a wide temperature range up to 1000 °C is demonstrated by using the differential pulse pair (DPP) Brillouin optical time domain analysis (BOTDA). Owing to the protection provided by the gold coating, the fiber can withstand high temperature environments and maintain a high strength, which enables the gold-coated fiber acting as a repeatable high-temperature sensor. After annealing twice to remove the internal stress, the temperature coefficient of the gold-coated fiber is stable and consistent with a nonlinear function. Owing to the residual stress accumulated during the cooling process of coating and the low yield strength of gold, a pre-pulling test is essential to measure the strain of a gold-coated fiber. An equal axial force model is used to recalculate the strain distribution induced by the large temperature difference within the furnace. The high-temperature strain coefficient of an annealed gold-coated fiber decreases with temperature, i.e. from ~0.046 MHz/μe at 100 °C to ~0.022 MHz/μe at 1000 °C, mainly due to the increase in Young’s modulus of silica with temperature. To the best of our knowledge, this is the first time that an annealed gold-coated fiber has been applied for distributed high-temperature strain sensing, which demonstrates the potential applications for strain monitoring in complex, high-temperature devices such as jet engines or turbines.

Posted Content
TL;DR: Time-domain Brillouin scattering is an all-optical experimental technique based on ultrafast lasers applied for generation and detection of coherent acoustic pulses on time durations of picoseconds and length scales of nanometers.
Abstract: Time-domain Brillouin scattering is an all-optical experimental technique based on ultrafast lasers applied for generation and detection of coherent acoustic pulses on time durations of picoseconds and length scales of nanometers. In transparent materials scattering of the probe laser beam by the coherent phonons permits imaging of sample inhomogeneity. The transient optical reflectivity of the sample recorded by the probe beam as the acoustic nanopulse propagates in space contains information on the acoustical, optical, and acousto-optical parameters of the material under study. The experimental method is based on a heterodyning where weak light pulses scattered by the coherent acoustic phonons interfere at the photodetector with probe light pulses of significantly higher amplitude reflected from various interfaces of the sample. The time-domain Brillouin scattering imaging is based on Brillouin scattering and has the potential to provide all the information that researchers in material science, physics, chemistry, biology etc., get with classic frequency-domain Brillouin scattering of light. It can be viewed as a replacement for Brillouin scattering and Brillouin microscopy in all investigations where nanoscale spatial resolution is either required or advantageous. Here we review applications of time-domain Brillouin scattering for imaging of nanoporous films, ion-implanted semiconductors and dielectrics, texture in polycrystalline materials and inside vegetable and animal cells, and for monitoring the transformation of nanosound caused by nonlinearity and focusing. We also discuss the perspectives and the challenges for the future.