Showing papers on "Brillouin scattering published in 2002"
TL;DR: In this article, the Brillouin scattering behavior in single-mode fibers with different waveguide characteristics in terms of their longitudinal mode structures in the gain spectrum, linewidth narrowing, and stimulated SBS threshold levels is investigated.
Abstract: We study the Brillouin scattering behavior in several single-mode fibers with different waveguide characteristics in terms of their longitudinal mode structures in the gain spectrum, linewidth narrowing, and stimulated Brillouin scattering (SBS) threshold levels. Evolution from spontaneous to SBS is investigated by monitoring the Brillouin line-shape and the behavior of the longitudinal acoustooptic resonance modes that exist in the core. We compare our results with the current theory of Brillouin scattering generated from noise in the undepleted pump approximation. We also present experimentally Brillouin gain spectra in the highly depleted pump regime, where there is no analytical solution, by showing the evolution of the gain spectrum as a function of the injected laser intensity.
265 citations
TL;DR: In this article, the spatial resolution of Brillouin strain sensing was improved by the correlation-based continuous-wave technique, which is applicable to smart structures or materials as a nervous system to monitor strain distribution.
Abstract: This letter describes improvement in the spatial resolution of distributed fiber Brillouin strain sensing by the correlation-based continuous-wave technique, which we proposed previously. The spatial resolution of 1 cm has been achieved for a partly stretched fiber. This result shows the technique is applicable to smart structures or materials as a nervous system to monitor strain distribution.
221 citations
TL;DR: A novel shape-adjustable narrowband optical filter utilizing stimulated Brillouin scattering in an optical fiber is proposed and demonstrated and a tunable optical notch filter is also realized by deamplification of the anti-Stokes wave.
Abstract: A novel shape-adjustable narrowband optical filter utilizing stimulated Brillouin scattering in an optical fiber is proposed and demonstrated. In this scheme, binary-phase-shift-keying modulation is applied to the pump wave to broaden and shape the Brillouin gain spectrum. By choosing an appropriate modulation data pattern, we realized a flat-top steep-cutoff optical bandpass filter with a 3-dB bandwidth of 1.5 GHz and a 10-dB bandwidth of 2 GHz is realized. In addition, a tunable optical notch filter is also realized by deamplification of the anti-Stokes wave.
145 citations
TL;DR: The velocities of the transverse and longitudinal acoustic modes of silica glass and liquid have been measured by Brillouin spectroscopy from 300 to 2300 K.
Abstract: The velocities of the transverse and longitudinal acoustic modes of silica glass and liquid have been measured by Brillouin spectroscopy from 300 to 2300 K. Elastic properties of liquid SiO2 could thus be studied over an interval of 800 K above the standard glass transition temperature. The velocity of the transverse mode, and thus the shear modulus, first increases with temperature and then decreases after reaching a maximum near the glass transition temperature. The velocity of the longitudinal mode and the bulk modulus, in contrast, continuously increase up to the maximum temperatures investigated. This unusual increase of the bulk modulus with temperature becomes less strong above 900 K. The vibrational (high frequency) contribution to the compressibility of the liquid, which is about three times smaller than the configurational (static) part, is thus insensitive to the configurational state of the liquid.
117 citations
TL;DR: The second-order elastic constants of CaF2 (fluorite) have been determined by Brillouin scattering to 9.3 GPa at 300 K as discussed by the authors.
Abstract: The second-order elastic constants of CaF2 (fluorite) have been determined by Brillouin scattering to 9.3 GPa at 300 K. Acoustic velocities have been measured in the (111) plane and inverted to simultaneously obtain the elastic constants and the orientation of the crystal. A notable feature of the present inversion is that only the density at ambient condition was used in the inversion. We obtain high-pressure densities directly from Brillouin data by conversion to isothermal conditions and iterative integration of the compression curve. The pressure derivative of the isentropic bulk modulus and of the shear modulus determined in this study are 4.78 ± 0.13 and 1.08 ± 0.07, which differ from previous low-pressure ultrasonic elasticity measurements. The pressure derivative of the isothermal bulk modulus is 4.83 ± 0.13, 8% lower than the value from static compression, and its uncertainty is lower by a factor of 3. The elastic constants of fluorite increase almost linearly with pressure over the whole investigated pressure range. However, at P ≥ 9 GPa, C
11 and C
12 show a subtle structure in their pressure dependence while C
44 does not. The behavior of the elastic constants of fluorite in the 9–9.3 GPa pressure range is probably affected by the onset of a high-pressure structural transition to a lower symmetry phase (α-PbCl2 type). A single-crystal Raman scattering experiment performed in parallel to the Brillouin measurements shows the appearance of new features at 8.7 GPa. The new features are continuously observed to 49.2 GPa, confirming that the orthorhombic high-pressure phase is stable along the whole investigated pressure range, in agreement with a previous X-ray diffraction study of CaF2 to 45 GPa. The high-pressure elasticity data in combination with room-pressure values from previous studies allowed us to determine an independent room-temperature compression curve of fluorite. The new compression curve yields a maximum discrepancy of 0.05 GPa at 9.5 GPa with respect to that derived from static compression by Angel (1993). This comparison suggests that the accuracy of the fluorite pressure scale is better than 1% over the 0–9 GPa pressure range.
111 citations
TL;DR: In this article, x-ray reflectivity, surface Brillouin scattering, resonant Raman scattering, and electron energy loss spectroscopy can be used to measure consistently the structural and mechanical properties of 2-nm thin carbon films.
Abstract: Ultrathin 2-nm-thick carbon coatings are needed to increase the storage density in magnetic hard disks. We show how x-ray reflectivity, surface Brillouin scattering, resonant Raman scattering, and electron energy loss spectroscopy can measure consistently the structural and mechanical properties of these thin films. 2 nm films retain a Young’s modulus of 100 GPa.
90 citations
TL;DR: A kinetic model was developed to obtain an analytic solution of the line shape for monatomic gases, and good agreement with the experimental data was achieved.
Abstract: Coherent Rayleigh-Brillouin scattering in gases has been studied experimentally for the first time in the kinetic regime and shown to give line shapes that differ significantly from the spontaneous Rayleigh-Brillouin scattering. A kinetic model was developed to obtain an analytic solution of the line shape for monatomic gases, and good agreement with the experimental data was achieved.
89 citations
TL;DR: Lindl et al. as mentioned in this paper showed that backward stimulated Raman scattering (BSRS), in regimes of large linear Landau damping of the primary Langmuir wave, attains levels greatly exceeding the predictions of models based on fixed damping.
Abstract: Kinetic simulations and analysis show that backward stimulated Raman scattering (BSRS), in regimes of large linear Landau damping of the primary Langmuir wave, attains levels greatly exceeding the predictions of models based on fixed damping. These regimes are encountered in plasma conditions expected for target designs to be fielded at the National Ignition Facility [J. D. Lindl, Inertial Confinement Fusion (Springer-Verlag, New York, 1998)]. Trapped electrons in the Langmuir wave have the dual effect of reducing its damping, thereby enhancing the BSRS response, and saturating this response by phase detuning, a consequence of the trapping-induced, time-dependent, frequency shift. BSRS, then, occurs as a train of sub-picosecond pulses, arising from the competition between phase detuning and parametric regeneration. A simple three wave parametric model, including the effect of the nonlinear frequency shift and residual nonlinear damping, reproduces these essential features. A similar scenario applies to backward stimulated Brillouin scattering (BSBS). BSRS activity many orders of magnitude above noise level is found for intense laser speckles even when the primary Langmuir wave number times the Debye length is as high as 0.55. The simulation model consistently accounts for the competition of other instabilities, including BSBS, forward stimulated Raman scattering, and the Langmuir decay instability with cavitation.
87 citations
Patent•
31 Dec 2002
TL;DR: In this paper, a servo technique for concurrently providing wavelength locking and stimulated Brillouin scattering (SBS) suppression in an external cavity laser is presented. But the authors do not consider the effect of SBS suppression on the optical path length of the laser.
Abstract: A servo technique for concurrently providing wavelength locking and stimulated Brillouin scattering (SBS) suppression in an external cavity laser. Respective wavelength locking and SBS suppression signals are generated by a controller and combined into a composite drive signal. The composite drive signal is used to drive an optical path length adjustment element to modulate the optical path length of the laser cavity. The wavelength locking and SBS suppression portions of the drive signals produce concurrent modulations of the laser optical path length having different modulation frequencies and causing different frequency (wavelength) excursions. These modulations produce corresponding wavelength and intensity amplitude modulations in the laser's output. A feedback signal indicative of the intensity amplitude modulations is filtered to attenuate the portion of the signal due to the SBS suppression modulation, and is received as a tuning feedback signal by the controller. In response, the control provides a tuning adjustment signal to adjust the frequency of the laser.
83 citations
TL;DR: It is clearly demonstrated that stimulated Brillouin scattering is directly responsible for both fast transient dynamics of the laser and reduction of the lasers' pulse width.
Abstract: We have designed and performed an experiment that permitted direct observation of Brillouin backscattering in an Yb-doped double-clad fiber laser. Fifteen Brillouin-shifted frequencies were observed for the first time to our knowledge. We clearly demonstrate that stimulated Brillouin scattering is directly responsible for both fast transient dynamics of the laser and reduction of the laser's pulse width.
83 citations
TL;DR: The extended effective length for the relevant nonlinear processes from the distributed Raman gain and the reduced Brillouin threshold from the seeding effect of Rayleigh backscattered waves are considered to be the key factors that explain the operation of this structure.
Abstract: We investigate the dynamics of a novel multiwavelength generator in which cascaded-stimulated Brillouin scattering and Rayleigh scattering are automatically balanced to given an evenly spaced (9.4-GHz), highly flattened (<3-dB) optical frequency comb over a 57.2-nm span. The extended effective length for the relevant nonlinear processes from the distributed Raman gain and the reduced Brillouin threshold from the seeding effect of Rayleigh backscattered waves are considered to be the key factors that explain the operation of this structure.
TL;DR: Stimulated and spontaneous Brillouin scattering effects are investigated in the HF, and it is shown that the high lasing threshold is due mainly to reduction of the effective gain coefficient caused by structural nonuniformity along the fiber length.
Abstract: We demonstrate for what is believed to be the first time a Brillouin laser based on a holey fiber (HF). Using a simple Fabry-Perot resonator scheme containing a 73.5m long highly nonlinear HF with an effective area of 2.85µm2, we obtain a threshold of 125mW and a slope efficiency of ~70%. Stimulated and spontaneous Brillouin scattering effects are investigated in the HF, and we show that the high lasing threshold is due mainly to reduction of the effective gain coefficient caused by structural nonuniformity along the fiber length.
TL;DR: It is shown that the SBS spectral width and gain depend on the numerical aperture for both single-mode and multimode fibers, the functional dependencies of which are in good agreement with the model description of the phenomenon.
Abstract: We provide direct experimental evidence of waveguide-induced inhomogeneous spectral broadening of stimulated Brillouin scattering (SBS) in optical fiber. It is shown that the SBS spectral width and gain depend on the numerical aperture for both single-mode and multimode fibers, the functional dependencies of which are in good agreement with our model description of the phenomenon.
TL;DR: In this paper, the authors introduce the fundamentals of optical carrier Brillouin processing and discuss its applications to the field of microwave photonics, which is based on the control of the amplitude as well as the phase of the optical carrier of a modulated lightwave signal using the stimulated BrillouIN scattering effect.
TL;DR: The first Thomson-scattering measurements of the growth of ion-acoustic waves in well-characterized multi-ion-species plasmas consisting of gold and beryllium are reported, verifying linear kinetic theory and explaining the measured SBS reflectivity by nonlinear detuning of the SBS instability.
Abstract: We report the first Thomson-scattering measurements of the growth of ion-acoustic waves in well-characterized multi-ion-species plasmas consisting of gold and beryllium. We observe that only the berylliumlike mode grows, verifying linear kinetic theory. In addition, a twofold increase in ion temperature is measured when ion-acoustic waves are excited to large amplitudes by stimulated Brillouin scattering (SBS). This increase in ion temperature is a strong indication of hot ions due to trapping. We explain the measured SBS reflectivity by nonlinear detuning of the SBS instability due to these trapping effects.
TL;DR: Numerical simulations are performed to obtain statistical and spectral characteristics of stimulated Brillouin scattering initiated by Gaussian noise in single-mode optical fibers and reveal how the probability function of Stokes power, the power-correlation function, and the SBS spectra evolve as key parameters of the model vary, leading to a modification of Stoke field statistics.
Abstract: We performed numerical simulations to obtain statistical and spectral characteristics of stimulated Brillouin scattering (SBS) initiated by Gaussian noise in single-mode optical fibers. Recently published experimental spectra of SBS power [e.g., Phys. Rev. Lett.85, 1879 (2000)] are explained completely by a one-dimensional SBS model. We give a clear physical insight into the problem and, for what is to our knowledge the first time, reveal how the probability function of Stokes power, the power-correlation function, and the SBS spectra evolve as key parameters of the model vary, leading to a modification of Stokes field statistics.
TL;DR: In this paper, the SBS threshold energy, and damage threshold were measured in multimode glass fibers with core diameters between 25 and 200 μm, and high SBS reflectivities over 80% were obtained with 30 ns laser pulses at 1.06 μm wavelength.
TL;DR: In this paper, the stimulated Brillouin scattering (SBS) threshold in a dual-clad fiber amplifier with a single-mode core and an approximation is explored for calculation of the SBS threshold and numerical solutions for the coupled differential equations.
Abstract: Experimental measurements are presented of the stimulated Brillouin scattering (SBS) threshold in a dual-clad fiber amplifier with a single-mode core and an approximation is explored for calculation of the SBS threshold and numerical solutions for the coupled differential equations. Good agreement is shown between modeled and experimental data.
TL;DR: In this paper, a theoretical approach to describe stimulated Brillouin scattering (SBS) threshold in Raman-pumped optical fibers was developed, and the condition for the SBS threshold as a function of fiber parameters and the input power of forward and/or backward pump was derived.
Abstract: We develop a theoretical approach to describe stimulated Brillouin scattering (SBS) in Raman-pumped optical fibers. We derive the condition for the SBS threshold as a function of fiber parameters and the input power of forward and/or backward pump. A particular emphasis is given to the effect of the fiber length and unequal absorption coefficients for pump and signal wavelengths on the SBS threshold. Simple, yet accurate, analytical expressions for the SBS threshold in pumped fibers are also obtained. We show that in pumped fibers, the SBS threshold power is inversely proportional to the path-average integral of Raman gain. Validity ranges of derived formulas are considered in detail. The theoretical predictions are verified experimentally. The calculated values of the SBS threshold powers are in a good agreement with the measured threshold power in Raman-pumped dispersion-compensated fibers.
TL;DR: In this paper, the frequency spectrum of back-scattered laser light was analyzed using a scanning Fabry-Perot etalon and a strong dependence of the linewidth of the Brillouin shifted lines on temperature was found.
Abstract: In the frequency spectrum of light that is scattered in liquid water there is a central elastically scattered peak that is due mainly to scattering by suspended particles; and, there is a peak on each side of the central peak that is displaced by the Brillouin frequency shift. The Brillouin shift is a direct measure of sound speed. The linewidth of the Brillouin shifted lines is dependent on the bulk and shear viscosity of water as well as its density, thermal conductivity, and specific heat. The linewidth of the Brillouin peaks has been investigated in laboratory experiments over a range 1°C to 35°C. The frequency spectrum of back-scattered laser light was analysed using a scanning Fabry-Perot etalon. A strong dependence of the linewidth of the Brillouin shifted lines on temperature was found. In particular, for low temperatures in the range 10°C down to 1°C the linewidth shows an increase from 750 MHz to 1.4 GHz.
TL;DR: In this paper, the principles of measuring sound speed in the water by Brillouin scattering are analyzed, and the results of the measured results are in good agreement with classical methods.
Journal Article•
TL;DR: Experimental results show that the stimulated Brillouin scattering spectrum in an optical fiber is inhomogeneous, exhibiting spectral broadening and hole burning under cw monochromatic laser excitation.
TL;DR: In this article, an investigation under pressure and at room temperature of BaTiO 3 and KNbO 3 using angle-dispersive powder X-ray diffraction is reported.
01 Jan 2002
TL;DR: Raman spectroscopy is the study of inelastic scattering of light as discussed by the authors, which stems from a transfer of energy between the incident radiation field and the material under investigation.
Abstract: Raman spectroscopy is the study of inelastic scattering of light. The inelasticity stems from a transfer of energy between the incident radiation field and the material under investigation. The technique provides, amongst other things, important information about the vibrational state of matter. One of the most influential early investigations into light scattering was undertaken by Lord Rayleigh (1899). In this study it was shown that the intensity of elastically scattered light is strongly dependent on its wavelength. In fact an inverse fourth power dependence on wavelength was proved, and was subsequently called the Rayleigh law. The process of inelastic scattering was theoretically predicted by Brillouin (1922) and Smekal (1923). (In Brillouin scattering radiation couples with acoustic modes of a system.) Key observations of very weak inelastic scattering phenomena were made in a remarkable experiment undertaken by C. V. Raman together with K. S. Krishnan (1928). The experimental set-up comprised focussed, filtered sunlight as the source, a sample of neat liquid and a telescope as the detector. Soon after, Landsberg and Mandelstam (1928) reported inelastic scattering of light from quartz with Cabannes (1928), Rocard (1928), and Raman and Krishnan (1929) themselves also offering subsequent quantitative studies in various media. Several books provide excellent descriptions of the history of the Raman effect (Long, 1977; Ferraro and Nakamoto, 1994).
TL;DR: In this article, the Brillouin light scattering technique has been exploited in order to study the elastic properties of dielectric films used in microelectronics, such as silicon oxide, silicon oxinitride and silicon nitride films deposited on (1.0.0)-Si by different techniques.
TL;DR: Stimulated Brillouin scattering (SBS) shows strong evidence of electromagnetic wave seeding of side- and backscattering in multibeam, laser-plasma interaction experiments in plasmas relevant to future direct-drive-ignition experiments.
Abstract: We report on multibeam, laser-plasma interaction experiments in plasmas relevant to future direct-drive-ignition experiments. Six interaction beams are incident on preformed plasmas containing critical density. Stimulated Brillouin scattering (SBS) shows strong evidence of electromagnetic wave seeding of side- and backscattering. The data are also consistent with shared ion waves driven by the six symmetrically arranged interaction beams. Early SBS quenching is observed and attributed to the hydrodynamics of the plasma.
TL;DR: In this article, the high-frequency dynamics of Sr 0. 6 1 Ba 0. 3 9 Nb 2 O 6 were studied using the micro-Brillouin scattering technique to elucidate the uniaxial relaxor behavior.
Abstract: The high-frequency dynamics of Sr 0 . 6 1 Ba 0 . 3 9 Nb 2 O 6 are studied using the micro-Brillouin scattering technique to elucidate the uniaxial relaxor behavior. It is found that broad central peaks (CP's) appear at about400°C, which is much higher than the maximum temperature, T m ∼72 °C, of the dielectric constant along the unique polar z axis, and they remain down to -100 °C. The marked polarization dependence observed for CP's indicates that their origin is due to the thermally switching nano-size polar clusters whose polar axis is along the z axis. The CP intensity reveals a possible crossover from a high-temperature relaxor state to a low-temperature ferroelectric state. Brillouin frequency shifts and their linewidths indicate diffuse phase transition behavior around T m . The temperature variation of the elastic constants C 1 1 , C 3 3 , and C 4 4 is determined, and C 3 3 and C 4 4 are found to exhibit marked changes around T m .
09 Sep 2002
TL;DR: In this paper, a correlation-based continuous-wave technique for fiber optic distributed strain sensors using Brillouin scattering was proposed. But the correlation-and continuous-witching technique is not suitable for dynamic strain measurements.
Abstract: This paper describes a novel correlation-based technique for fiber optic distributed strain sensors using Brillouin scattering Conventional Brillouin-based sensors utilize a pulsed-pump similar to that of OTDR and are capable of distributed strain sensing over large distances, but suffer an inherent spatial resolution limit of around 1m In addition, unlike FBG-based strain sensors which are competent of measuring dynamic strain, the pulse-based Brillouin sensors have large measurement times of several minutes, making them inadequate for dynamic strain measurements On the other hand, using the correlation-based continuous-wave technique, we have achieved static distributed strain measurements of up to 1cm spatial resolution, and dynamic strain measurements of up to 88Hz from a 5cm strained section
TL;DR: The Brillouin gain spectrum is theoretically derived, that is, the Briilouin backscattered-light power spectrum produced in an optical fiber under conditions of a strain distribution that changes linearly with a constant slope, and the strain calculated from the frequency at which the spectrum has a peek value coincide.
Abstract: We theoretically derive the shape of the Brillouin gain spectrum, that is, the Brillouin backscattered-light power spectrum, produced in an optical fiber under conditions of a strain distribution that changes linearly with a constant slope. The modeled measurement system is an optical time-domain reflectometer-type strain sensor system. The linear strain distribution is one of the fundamental distributions and is produced in, for example, a beam to which a concentrated load is applied. By analyzing a function that expresses the shape of the derived Brillouin gain spectrum, we show that the strain calculated from the frequency at which the spectrum has a peak value coincides with that at the center of the effective pulsed light. In addition, the peak value and the full width at half-maximum of the Brillouin gain spectrum are both influenced by the strain difference between the two ends of the effective pulse. We investigate this influence in detail and obtain the relationship between strain difference and strain measurement error.