High Brillouin Research Articles

High efficiency Brillouin random fiber laser with replica symmetry breaking enabled by random fiber grating.

We report a high efficiency Brillouin random fiber laser (BRFL) enabled by a random fiber grating (RFG) with demonstration of replica symmetry breaking (RSB). The RFG was characterized by optical coherence tomography (OCT) method, which measured the spatially resolved reflectivity of RFG by a tunable delay line. Multiple narrow linewidth peaks appeared in reflection spectrum of RFG, created by frozen scattering centers acting as narrow linewidth filters to select random modes in random fiber lasers based on Brillouin gain. With the scattering from RFG as disordered feedback, a BRFL with slope efficiency of 29.3% and lasing threshold of 10.2 mW was demonstrated with 1 kHz linewidth. Intensity dynamics show that RFG can reduce the noise of BRFL with a symmetric phase portrait, indicating the increased mean path length and coherence time of the Stokes photons. The probability distribution of the Parisi overlap parameter of intensity fluctuation spectra from trace to trace reveal a photonic spin-glass phase with RSB in the RFG enabled BRFL, providing a photonic platform to study the photon glassy behavior of random fiber lasers.

Inter-Mode Forward Brillouin Scattering in Nanofibers

We investigate the inter-mode forward stimulated Brillouin scattering (FSBS) in nanofibers in this article. An extraordinary high Brillouin peak value is predicted for the interaction between the HE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> and the high-order optical mode (TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</sub> ). The corresponding excited acoustic mode (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ) has the characteristics of the relatively uniform large normalized displacements and the phase velocity less than the shear acoustic velocity of silica, which completely differs from the transverse acoustic mode in the intra-mode FSBS process of the HE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> . The Brillouin peak value by the contribution of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> can reach 260.5 W <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at a frequency of 0.1905 GHz, which is at least an order of magnitude higher than the maximum peak value in the intra-mode forward Brillouin gain spectrum (BGS). Moreover, for a nanofiber radius of 0.57 to 1 μm, the contribution of R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> is always the most prominent to the BGS. This work provides further insight into phonon-photon coupling in nanofibers.

P0666BRILLOUIN AND RAMAN SPECTROSCOPIES FOR NON-CONTACT ASSESSMENT OF MECHANO-CHEMICAL PROPORTIES OF URINARY PROTEINS: A PROOF OF CONCEPT STUDY

Abstract Background and Aims Proteinuria is a major marker of chronic kidney disease (CKD) severity, the predictor of renal function decline and cardiovascular mortality. The main pathway of CKD progressive is caused by tubular toxicity of filtering proteins, so more, the rapid development of renal failure is expected in those patients who have higher level of proteinuria. However, despite high level of proteinuria, paradoxically, some patients may have slow decline of renal function compared to those patients with lower level of urinary protein excretion. This may possibly due to their different mechanical (visco-elastic) and chemical properties, as well as the proteomics of excreting urinary proteins. Brillouin light scattering (BLS) and surface enhanced Raman scattering (SERS) spectroscopies are non-contact (laser optical-based) techniques providing visco-elastic and chemical property information of probed human biofluids. We aimed to study and compare the visco-elastic and chemical properties of urinary proteins using BLS and SERS spectroscopies in nephrotic patient with high protein excretion and healthy subject. Method Two urine samples from nephrotic patient (proteinuria&amp;gt;3.5 g/24h) and healthy subject (undetectable proteinuria) investigated using BLS and SERS spectroscopies. Brillouin spectroscopy performed using Torus single longitudinal mode laser in conjunction with high contrast JRS Instruments 6-pass tandem Fabry-Perot interferometer coupled with confocal microscope. Using Horiba LabRAM HR Raman microscope with 785 nm laser excitation andx100 microscope objective the SERS spectroscopy was performed on urine samples in contact 60 nm gold nanoparticles placed on gold film. Additionally, reversed-phase liquid chromatography-mass spectrometry (LC-MS) was conducted for profiling of urinary proteins LC-MS data was analysed by Mascot software using the SwissProt protein database. Results We found that elevated protein levels in urine alter the urine fluid elasticity sufficiently to be measurable by BLS spectroscopy, with urine from healthy and proteinuric subjects distinguishable to marked significance, which increases with sample concentration. BLS spectroscopy demonstrated that patients with High Protein Loss, characterized by stiffer urine (i.e. higher Brillouin shift and elastic modulus) and less viscous (i.e. less hypersound attenuation) compared to healthy subject. (Figure 1A). SERS measurements of two urine samples taken from patient with high protein loss in healthy subject (Figure 1B) showed the integrated Raman intensity ratio of 1338 cm-1 and 1002 cm-1 peaks is many times higher for the sample with high protein concentration vs sample with low protein concentration. Urinary protein sequencing and Mascot analysis (Table 1) demonstrated that proteinuric patient had different type of proteins with up to 187k Daltons of molecular weight. Conclusion In this proof of concept study, we demonstrated that laser-optical BLS and SERS techniques combined with LC-MS measurements revealed that human urine fluids of healthy and proteinuric subjects had strong variation in the visco-elastic and chemical properties coupled with various level of protein content.

Widely triple Brillouin frequency shift multiwavelength Brillouin erbium fiber laser

We experimentally propose simple and widely tunable multiwavelength Brillouin erbium fiber laser with triple Brillouin frequency spacing. Only two dispersion compensation fiber spools with total length of 12 km, as a Brillouin gain media and erbium-doped fiber amplifier section with maximum pump power of 220 mW are utilized. In the developed structure, we achieved six triple Stokes lines with high peak power and large optical signal to noise ratio of more than 45 dB. Wide tuning range of 50 nm (1530–1580 nm) in the absence of self lasing cavity modes is recorded using both of high Brillouin pump and extracting the residual pump power outside the cavity.

Diamond Brillouin laser in the visible

Brillouin lasers providing extremely narrow-linewidth are emerging as a powerful tool for microwave photonics, coherent communications, quantum processors, and spectroscopy. So far, laser performance and applications have been investigated for a handful of select materials and using guided-wave structures such as micro-resonators, optical fibers, and chip-based waveguides. Here, we report a Brillouin laser based on free-space laser action in an extreme optical material. Continuous-wave lasing 167 GHz from a 532 nm pump is demonstrated in diamond using a doubly resonant ring cavity, generating a pump-limited output power of 11 W. The Brillouin gain coefficient is measured to be 79 cm GW−1 with a linewidth of 12 MHz. These properties, along with an exceptionally high Brillouin frequency and wide transmission range, make diamond Brillouin lasers a promising high-power source of narrow-linewidth output and mm-wave beat notes.

Tunable and Switchable Multi-wavelength Erbium-Brillouin Random Fiber Laser Incorporating a Highly Nonlinear Fiber

A tunable and switchable multi-wavelength Erbium–Brillouin random fiber laser (MW-EBRFL) with a half-open cavity structure and incorporating a segment of highly nonlinear fiber (HNLF) is proposed and experimentally demonstrated. Due to HNLF being with high nonlinear coefficient, high Brillouin gain coefficient and high Rayleigh scattering (RS) coefficient, a reduced length of HNLF can provide a strong random distributed feedback (RDFB) and high stimulated Brillouin scattering (SBS) gain. In addition, an optical fiber amplify loop (OFAL) including a high-power erbium-doped fiber amplifier (HP-EDFA) and an optical attenuator (ATT) is constructed to provide a strong Brillouin pump (BP) and controllable optical feedback. Using the presented MW-EBRFL, up to 11 orders of stable Stokes laser lines with a wavelength spacing of 0.074 nm and the minimum optical signal-to-noise ratio (OSNR) of 41.22 dB are obtained. System parameters including BP power and HP-EDFA pump power influence on output of MW-EBRFL are also investigated. By adjusting BP wavelength, multi-wavelength output with 6–11 channel numbers can be tuned in a wide wavelength range spanning 36 nm. The proposed MW-EBRFL also can realize switchable multi-wavelength generation of 1 ∼ 11 order Stokes with an increasing wavelength number in turn, only by simply adjusting HP-EDFA pump power. Furthermore, when a polarization-maintaining fiber loop mirror filter (PMF-LMF) is cascaded with output port of the cavity, it can be very convenient to achieve wavelength switching between single- and double-Brillouin frequency spacing (BFS), only by tuning polarization controller in PMF-LMF.

Large on-chip Brillouin net amplification in silicon-based nano-photonics

Recent developments in on-chip forward Brillouin scattering open up potential applications such as RF photonic signal processing, on-chip Brillouin amplification, and on-chip Brillouin lasers. The stimulated Brillouin scattering gain coefficients become significant with a small optical mode area, and the Brillouin net amplification has been believed to be strong with a small mode area, too. However, here, we present a theoretical study of higher net amplification with a large optical mode area than that with a small mode area and explain this counter-intuitive phenomenon by examining the contribution of various optical forces to Brillouin gain coefficients for various optical waveguide dimensions. The simulation results show that a waveguide with large optical waveguide dimensions can yield significant net amplification by high Brillouin gain coefficients and low optical losses at high pump power even if the Brillouin gain coefficients are lower than that with a small waveguide dimension. Therefore, it is necessary to optimize the optical waveguide dimensions to achieve maximum net amplification for the development of Brillouin lasers and amplifiers in silicon-based nanophotonics.

High birefringent Brillouin frequency shifts in a single-mode As2Se3-PMMA microtaper induced by a transverse load.

We report high Brillouin frequency shifts of 0.08±0.02 MHz/N in a 60cm As2Se3-Poly(methyl methacrylate) (As2Se3-PMMA) hybrid microtaper with 2μm As2Se3 core and 100μm PMMA cladding diameters under a transverse load. Through finite element analysis of stimulated Brillouin scattering under the influence of contact stress from the loading fixture, such shifts are in accordance with a numerical value of 0.06±0.01 MHz/N. Further numerical analysis shows that uncertainties in the Brillouin frequency shift are the result of birefringence that is 27 times stronger than what is found in standard silica fibers.

System-Level Performance of Chip-Based Brillouin Microwave Photonic Bandpass Filters

Microwave photonic (MWP) filters using on-chip stimulated Brillouin scattering offer great potential for next-generation radio frequency (RF) applications due to the unprecedented high spectral resolution, flexible programmability, and ultra-wideband frequency agility. Although impressive functionalities have been reported, limited link performance, due to the amplification noise induced by the Brillouin gain process, hinders the practical deployment in existing RF applications. In this paper, we present the first comprehensive numerical and experimental study of chip-based Brillouin MWP bandpass filters implemented in a range of link configurations. In the experiments, key RF performance figures of merit, including link gain, noise figure, passband resolution, bandwidth tunability, and passband extinction of chip-based Brillouin filters are experimentally investigated and numerically analyzed. This comprehensive study points out a preferable filter scheme with optimized system-level performance. The numerical model developed in this paper allows for extrapolations to further improve the performance. The systematic work establishes a feasible design route for achieving high link-performance chip-based Brillouin microwave photonic bandpass filters.

Broadly tunable 40 GHz Brillouin frequency spacing multiwavelength Brillouin–Erbium fiber laser for DWDM

In this paper, we propose and experimentally demonstrate quadruple Brillouin-shift wavelength spacing (˜0.33 nm, ˜40 GHz) utilizing multiwavelength Brillouin–Erbium fiber laser (MBEFL) cavity. High Brillouin pump (BP) power, Pre-amplification technique, and capturing the residual pump power using wave selective coupler (WSC) are used to enhance laser comb tunability. The proposed structure has a tuning range of 60 nm (1530 nm–1590 nm) in the absence of self lasing cavity modes. Four stable Brillouin Stokes with high output power are achieved at 20mW and 225mW of BP and 1480 nm pump power respectively. In addition, multi-output ports with quadruple channel spacing is presented. This wide channel spacing make the proposed structure has strong potential to be used in dense wavelength division multiplexing (DWDM) communication systems.

High-performance optical chirp chain BOTDA by using a pattern recognition algorithm and the differential pulse-width pair technique

Optical chirp chain Brillouin optical time-domain analysis (OCC-BOTDA) has the capabilities of fast measurement, high Brillouin threshold, and freedom from the nonlocal effect; at the same time, however, it also has problems introduced by transient stimulated Brillouin scattering. The influence of the transient interaction is reflected as the broadened asymmetric Brillouin spectrum, the ghost peak, and the frequency shift of the main peak. This introduces difficulty in computing the fiber Brillouin frequency shift with good measurement accuracy. Besides, the OCC modulation causes additional noise due to the uneven amplitude response for different frequency components. In this work, we propose a high-performance OCC-BOTDA using the principal component analysis (PCA) based pattern recognition algorithm and differential pulse-width pair (DPP) technique. After building the Brillouin spectrum database (i.e., all patterns), the fiber intrinsic Brillouin frequency shift can be recognized by the PCA algorithm from a nonstandard Brillouin spectrum profile, resulting in good measurement accuracy. Meanwhile, the DPP technique, subtracting between two Brillouin signals generated by two wide-width pump pulses, is utilized to reduce the OCC modulation noise and avoid the pulse self-phase modulation effect in long-range BOTDA sensing. In the experiment, a temperature measurement with 1.3 MHz measurement precision, 4 m spatial resolution, and 5 s measurement time is achieved over a 100 km single-mode fiber.

Anisotropic magnetic excitations and incipient Néel order in Ba(Fe1−xMnx)2As2

It is currently understood that high temperature superconductivity (SC) in the transition metal $(M)$ substituted iron arsenides Ba(Fe$_{1-x}$$M$$_{x}$)$_{2}$As$_{2}$ is promoted by magnetic excitations with wave vectors $(\pi,0)$ or $(0,\pi)$. It is known that while a small amount of Co substitution leads to SC, the same does not occur for Mn for any value of $x$. In this work, magnetic excitations in the iron arsenides Ba(Fe$_{1-x}$Mn$_{x}$)$_{2}$As$_{2}$ ($x=0.0$, $0.007$, $0.009$, $0.08$) are investigated by means of Resonant Inelastic X rays Scattering (RIXS) at the Fe $L_{3}$-edge, for momentum transfer $\boldsymbol{q}$ along the high symmetry Brillouin zone $(\pi,0)$ and $(\pi,\pi)$ directions. It is shown that with increasing Mn content ($x$), the excitations become anisotropic both in dispersion and lineshape. Both effects are detected even for small values of $x$, evidencing a cooperative phenomenon between the Mn impurities, that we ascribe to emerging N\'eel order of the Mn spins. Moreover, for $x=0.08$, the excitations along $\boldsymbol{q}\parallel(\pi,0)$ are strongly damped and nearly non dispersive. This result suggests that phases of arsenides containing local moments at the FeAs layers, as in Mn or Cr substituted phases, do not support high temperature SC due to absence of the appropriate magnetic excitations.

Long-term Brillouin imaging of live cells with reduced absorption-mediated damage at 660 nm wavelength.

In Brillouin microscopy, absorption-induced photodamage of incident light is the primary limitation on signal-to-noise ratio in many practical scenarios. Here we show that 660 nm may represent an optimal wavelength for Brillouin microscopy as it offers minimal absorption-mediated photodamage at high Brillouin scattering efficiency and the possibility to use a pure and narrow laser line from solid-state lasing medium. We demonstrate that live cells are ~80 times less susceptible to the 660 nm incident light compared to 532 nm light, which overall allows Brillouin imaging of up to more than 30 times higher SNR. We show that this improvement enables Brillouin imaging of live biological samples with improved accuracy, higher speed and/or larger fields of views with denser sampling.

Thermoelectric response of ZrNiSn and ZrNiPb Half-Heuslers: Applicability of semi-classical Boltzmann transport theory

Abstract We investigated the thermoelectric transport mechanism of ZrNiSn and ZrNiPb Half-Heuslers within the Boltzmann transport theory, under constant relaxation time approximation. The prediction of band structure behavior along the high symmetry Brillouin zone and density of states are used to establish relations among various transport coefficients like Seebeck coefficient, electrical conductivity, thermal conductivity and power factor which have been found to be in good agreement with the experimental results. The Seebeck coefficient variation show the n-type behavior of heat carriers. The electrical and thermal conductivity show a semiconducting nature of bands along the Fermi level. The lattice part of thermal conductivity show an exponential decreasing trend along the high temperatures. Power factor variation and figure of merit show the heavier element doping of ZrNiSn results in descent increase in efficiency triggering its applicability. The overall measurements show that semi classical Boltzmann transport theory has well behaved potential in predicting the transport properties of the compounds.

Elastic properties of single crystal hydrogen sulfide: A Brillouin scattering study under high pressure-temperature

We have performed high pressure-temperature Brillouin scattering measurements on single crystal hydrogen sulfide using externally heated diamond anvil cell techniques. The pressure dependences of the acoustic velocities, isothermal elastic constants, and moduli of single crystal hydrogen sulfide have been determined along four isotherms. Both elastic constants and moduli increase monotonously with pressure along each isotherm, while they show a decreased tendency with temperature elevated under the same pressure points. The experimental equation of state of single crystal hydrogen sulfide is obtained by fitting with a third-order Birch-Murnaghan and Tait equation. It is proposed that the effect of hydrogen bonds contributes to the unique tendency of elastic anisotropy in single crystal hydrogen sulfide. Through our work, we have extended the melting curve and phase diagram of hydrogen sulfide up to 12 GPa and 580 K.

150 km fast BOTDA based on the optical chirp chain probe wave and Brillouin loss scheme.

Distributed long-range Brillouin optical time domain analysis (BOTDA) is an extremely time-consuming sensing scheme, which requires frequency mapping of the Brillouin spectrum and a large number of average times. Here, we propose a fast long-range BOTDA based on the optical chirp chain (OCC) probe wave and Brillouin loss scheme. The OCC-modulated probe wave is enabled by cascading fast-frequency-changing microwave chirp segments head-to-tail, which covers a large frequency range around the anti-Stokes frequency relative to the pump wave. The combination of the OCC technique and Brillouin loss scheme provides several advantages, i.e., fast measurement, a high Brillouin threshold, no additional amplification scheme, and freedom from the nonlocal effect. In the experiment, 6m spatial resolution, 3.2s measurement time, and 3MHz measurement precision were achieved over a 150km single-mode fiber.

Acoustic properties and density of polyurea at pressure up to 13.5 GPa through Brillouin scattering spectroscopy

Brillouin scattering was performed on an elastomeric polyurea, an important technological polymer. Being widely used for impact modification, of particular interest is its response to extreme pressure conditions. We applied pressures up to 13.5 GPa using a diamond anvil cell and measured the longitudinal and transverse sound velocities via Brillouin light scattering. From these data, the equation of state, the elastic moduli, and Poisson's ratio were obtained. By comparison with previous dilatometry measurements up to 1 GPa, we show how viscoelastic effects can be accounted for in order to obtain an accurate equation of state. Because of the extreme strain-rate hardening of vitrifying polyurea, the property changes associated with its solidification are more subtle in the high frequency Brillouin data than observed in conventional mechanical testing and dilatometry.

Brillouin comb generation in a ring cavity with tellurite single mode fiber

We experimentally demonstrate tunable Brillouin comb generation in a ring cavity composed of a piece of tellurite single mode fiber. The tunable Brillouin comb lines are separated with frequency space of 7.9 GHz, which is equal to the Brillouin frequency shift in the tellurite fiber. Due to the high Brillouin gain coefficient of the tellurite fiber, a tellurite fiber as short as 200 m was inserted into the ring cavity. Cascaded stimulated Brillouin Stokes and anti-Stokes lines are generated in the ring cavity leading to multi-wavelength Brillouin comb generation bi-directionally. By tuning the narrow-linewidth tunable laser, we can tune the Brillouin comb in the wide range of 1533 nm to 1565 nm.

Chemical Potential Evaluation of Thermoelectric and Mechanical Properties of Zr2CoZ (Z = Si, Ge) Heusler Alloys

The electronic, mechanical and thermoelectric properties of Zr2CoZ (Z = Si, Ge) Heusler alloys are investigated by the full-potential linearized augmented plane wave method. Using the Voigt–Reuss approximation, we calculated the various elastic constants, the shear and Young’s moduli, and Poisson’s ratio which predict the ductile nature of the alloys. Thermoelectric coefficients viz., Seebeck, electrical conductivity and figure of merit show Zr2CoZ alloys as n-type thermoelectric materials showing a linearly increasing Seebeck coefficient with temperature mainly because of the existence of almost flat conduction bands along L to Г directions of a high symmetry Brillouin zone. The efficiency of conversion was measured as the figure of merit by taking into effect the lattice thermal part that achieves an upper-limit of 0.14 at 1200 K which may favour their use for waste heat recovery at higher temperatures.

Insight into mechanical properties and thermoelectric efficiency of Zr2CoZ (Z = Si, Ge) Heusler alloys

We investigated the electronic, mechanical and thermoelectric properties of Zr2CoZ (Z = Si, Ge) Heusler alloys using the first-principles calculation. From the analysis of various elastic constants, the shear and Young’s moduli, Poisson’s ratio, the ductile nature of the alloys is predicted. Thermoelectric coefficients viz., Seebeck, electrical conductivity and figure of merit show Zr2CoZ alloys as n-type thermoelectric materials showing linearly increasing Seebeck coefficient with temperature. The value of total absolute Seebeck coefficients at 1200 K of Zr2CoSi and Zr2CoGe are 60 µV K−1 and 40 µV K−1 respectively mainly because of the existence of almost flat conduction bands along L to Г directions of high symmetry Brillouin zone. Further, the chemical potential variation of power factor confirms the n-type doping fruitful to increase their TE performance. The figure of merit achieves an upper-limit of 0.95 at 850 K and can favour their use for waste heat recovery at higher temperatures and thermoelectric spin generators.