Stimulated Brillouin scattering materials, experimental design and applications: A review

Abstract

Stimulated Brillouin scattering (SBS), as one type of third-order nonlinear optics effect, is extensively exploited and rapidly developed in the field of lasers and optoelectronics. A large number of theoretical and experimental studies on SBS have been carried out in the past decades. Especially, the exploration of new SBS materials and new types of SBS modulation methods have been engaged simultaneously, as the properties of different materials have great influence on the SBS performance such as generation threshold, Brillouin amplification efficiency, frequency shift, breakdown threshold, etc. This article provides a comprehensive review of the characteristics of different types of SBS materials, SBS applications, experimental design methods, as well as the parameter optimization method, which is expected to provide reference and guidance to SBS related experiments.

Introduction

Stimulated Brillouin scattering (SBS) is well known for its excellent performance in phase conjugation, pulse compression, beam shaping (temporal and spatial), Brillouin-enhanced four-wave-mixing (BEFWM), slow light and beam combination [1], [2], [3], [4], [5]. For instance, SBS phase conjugate mirrors (SBS-PCMs) can be adopted to compensate a beam distortion caused by optical elements in the system, which would improve brightness and performance of high power lasers. This permits applications of high power lasers in fields requiring high-quality beam delivery such as LIDAR, space communication, and laser fusion [6], [7]. Distributed optical fiber sensors based on Brillouin amplification are currently in development for high accuracy and high-resolution sensing of temperature and stress in engineering [8], [9]. In addition, SBS is also an efficient method to compress optical pulses from up to 10 ns to hundreds of picoseconds, which is considered to be a promising approach to obtain an ignitor-shock spike for the inertial confinement fusion [10], [11]. Additionally, serial laser beam combination based on SBS allows increasing the power of lasers far beyond that of a single gain medium, without having to control the phase of each beam [12], [13]. Compared with other methods, such as polarized combination or multi-wavelength combination, serial laser beam combination provides the possibility of generating giant pulse output with the highest flexibility. Despite all of its benefits, SBS is also known as a detrimental phenomenon in communication fibers and fiber amplifiers which limits their maximum power and transmission rate [14], [15], [16]. Therefore, various methods have also been developed to suppress SBS [17], [18], [19].

One or several scattering processes—Rayleigh scattering, Brillouin scattering, and Raman scattering, can occur due to the interaction of an incident wave with a medium [20]. When the intensity of light is low the resulting scattering process will be spontaneous. However, when the incident intensity reaches a certain threshold, stimulated scattering will be observed with a strong interaction between light fields and matter. As one of the third-order nonlinear optical effect, SBS phenomena has been observed when intense laser light interacts with materials in gaseous, liquid, solid or plasma states. The process of SBS is the result of the interaction between an intense incident light wave and elastic acoustic waves in a medium. Therefore, the intrinsic properties of a medium have a significant impact on SBS performance. To date, a large number of SBS media have been adopted to explore the optimum parameters in a wide variety of experiments. Important parameters affecting the selection of SBS materials for a given application include the pumping conditions, the SBS gain coefficient, the optical damage threshold, the transmission wavelength, size constraints, etc. Although SBS media in the same state of matter have similar characteristics in many cases, SBS properties of a given material under different circumstances can vary widely [21], [22]. Therefore, it is important to select the appropriate SBS medium according to specific requirements. Depending on the different types of materials adopted, different designs for the SBS cell and experimental setup will be desirable. Fig. 1 illustrates the timeline of major advances in SBS, including milestones of different media discovered, platforms and applications. In the 1920s, theoretical predictions of an inelastic scattering of light from acoustic phonons were made by Brillouin [23] and Mandelstam [24]. However, the strong requirement of an intense and narrow linewidth light source prevented SBS to be experimentally observed until 1964 in bulk medium [25], shortly after the invention of a laser [26]. Subsequently, SBS was demonstrated in a number of different media including liquids [27], [28], [29], gases [30], and fibers [15]. To improve SBS performance, new media are exploited such as heavy fluorocarbon liquids [31], chalcogenides [32], photonic crystal fibers (PCF) [33], on-chip waveguides [34], silicon [35], and diamond [36]. Meanwhile, increasing number of applications employ SBS including narrow linewidth Brillouin lasers [37], pulse compression [38], distributed sensing [39], beam cleanup [40], serial beam combination [41], and fast and slow light [42]. Although, there have been numerous reviews on SBS, recent advances in materials science and photonics call for a review of more recent work in this growing field, as well as descriptions of new experimental designs. Due to largely different properties of plasma-based SBS experimental methods and materials, they are not within the scope of the presented publication, which focusses on gaseous, liquid and solid media.

This paper reviews the working principles and applications of SBS, various physical and SBS-related characteristics of different media, experimental methods, and design of SBS devices. The intention of this review is to provide a guide on SBS medium selection and experimental design to enable a highly stable, and highly efficient SBS generation in applications. The paper is arranged as follows: this section provides the introduction and outline; the theory and working principles of SBS are given in Section 2; Section 3 covers SBS applications in many fields such as phase conjugation, pulse compression, beam combination and distributed optical fiber sensor; Section 4 discusses the properties of different SBS media, as well as experimental design and optimization methods; and Section 5 presents the overall summary of this paper.