Brillouin scattering

About: Brillouin scattering is a research topic. Over the lifetime, 11426 publications have been published within this topic receiving 178306 citations.

Forced Brillouin Spectroscopy Using Frequency-Tunable Continuous Wave Lasers.

Abstract: We have developed a new method of phonon spectroscopy using forced Brillouin scattering: A scanning interference pattern produced by intersecting two cw lasers generates the density variation (acoustic phonons) through the thermal expansion for a light-absorbing liquid. When the dispersion relation of phonons is satisfied, phonons are generated resonantly in the liquid. Continuous tuning of the frequency difference between the two lasers enables us to measure a resonance spectrum of light-excited phonons using light scattering phenomena. We demonstrate that this resonance spectrum is equivalent to the Brillouin spectrum of thermal phonons both experimentally and theoretically.

Acoustic confinement and stimulated Brillouin scattering in integrated optical waveguides

Abstract: We examine the effect of acoustic mode confinement on stimulated Brillouin scattering (SBS) in optical waveguides that consist of a guiding core embedded in a solid substrate. We find that SBS can arise due to coupling to acoustic modes in three different regimes. First, the acoustic modes may be guided by total internal reflection; in this case, the SBS gain depends directly on the degree of confinement of the acoustic mode in the core, which is in turn determined by the acoustic V parameter. Second, the acoustic modes may be leaky but may nevertheless have a sufficiently long lifetime to have a large effect on the SBS gain; the lifetime of acoustic modes in this regime depends not only on the contrast in acoustic properties between the core and the cladding but is also highly dependent on the waveguide dimensions. Finally, SBS may occur due to coupling to free modes, which exist even in the absence of acoustic confinement; we find that the cumulative effect of coupling to these nonconfined modes results in significant SBS gain. We show how the different acoustic properties of core and cladding lead to these different regimes and discuss the feasibility of SBS experiments using different material systems.

Elasticity of microcrystals

Abstract: Acoustic velocities for a very small crystal are presented. The longitudinal velocities in the .3 mm single crystal of quartz are accurate to about 1–2%. The technique involves only optical measurements and is based on analysis of Brillouin scattering. The minimal sample size for acoustic velocity measurements using this technique is estimated to be about 0.01–0.03 mm.

Distributed Brillouin sensing with sub-meter spatial resolution: modeling and processing

Abstract: A general analytic solution for Brillouin distributed sensing in optical fibers with sub-meter spatial resolution is obtained by solving the acoustical-optical coupled wave equations by a perturbation method. The Brillouin interaction of a triad of square pump pulses with a continuous signal is described, covering a wide range of pumping schemes. The model predicts how the acoustic wave, the signal amplitude and the optical gain spectral profile depend upon the pumping scheme. Sub-meter spatial resolution is demonstrated for bright-, dark- and π-shifted interrogating pump pulses, together with disturbing echo effects, and the results compare favorably with experimental data. This analytic solution is an excellent tool not only for optimizing the pumping scheme but also for post-processing the measured data to remove resolution degrading features.

Reduction of Guided Acoustic Wave Brillouin Scattering in Photonic Crystal Fibers

Abstract: Guided acoustic wave Brillouin scattering (GAWBS) generates phase and polarization noise of light propagating in glass fibers. This excess noise affects the performance of various experiments operating at the quantum noise limit. We experimentally demonstrate the reduction of GAWBS noise in a photonic crystal fiber in a broad frequency range by tailoring the acoustic modes using the photonic also as a phononic crystal. We compare the noise spectrum to the one of a standard fiber and observe a tenfold noise reduction in the frequency range up to 200 MHz. Based on our measurement results as well as on numerical simulations, we establish a model for the reduction of GAWBS noise in photonic crystal fibers.