高非线性光子晶体光纤具有小纤芯、大折射率对比度的特点,其周期性的空气孔结构使得导引声波布里渊散射(GAWBS)激发的声子被束缚在纤芯区域,产生显著的声光相互作用。声子通过调制光纤材料的折射率,从而对光波的相位进行调制。利用Sagnac干涉环将相位调制转化为强度调制,在光子晶体光纤中实现了1550 nm和1060 nm波段GAWBS声子的激发和探测。实验测得在1550 nm和1060 nm波长抽运下声子基模频率均约为1.24 GHz,验证了前向布里渊散射声子频率与抽运光波长无关的理论。

Highly nonlinear photonic crystal fibers have the characteristics of small core and large refractive index contrast. Due to its periodic air hole structure, the phonons generated by the guided acoustic-wave Brillouin scattering (GAWBS) are tightly trapped in the core area and interact significantly with photons. The refractive index of the fiber will be modulated by phonons, resulting in a phase modulation on optical waves. Using the Sagnac interferometry to transform phase modulation to intensity modulation, we demonstrate the generation and detection of phonons by GAWBS in the photonic crystal fiber in the 1550 nm and 1060 nm bands, respectively. The experimental results show that the fundamental mode frequency of acoustic phonons is 1.24 GHz for both cases with the pump wavelengths of 1550 nm and 1060 nm, respectively, which verifies the theory that the phonon frequency in forward Brillouin scattering is independent of the pump wavelength.