消偏器是光纤传感器、光放大器等偏振敏感性光学系统中的关键器件, 用于减小输入光的偏振度(DOP)。设计了一种与入射线偏振光振动方向无关的低偏振度消偏器, 该器件中利用人为的偏振相关延迟代替了保偏光纤的双折射, 并在偏振相关型消偏器前增加了一个1/4波片, 从而对任意方向振动的线偏振光具有相同的消偏能力, 结构紧凑。对消偏性能随波片阶数、入射光中心波长和振动方向的变化作了数值计算。实验中采用半峰全宽为0.13 nm的光源, 入射线偏振光在任意方向振动时, 输出光偏振度小于2.6％, 消偏器的插入损耗为0.6 dB, 损耗起伏小于0.11 dB。实验和数值计算结果表明, 该消偏器具有低偏振度、低插入损耗和适合于宽光谱应用的优点。

Depolarizer is a key device in polarization sensitive optical systems, by which a completely or partially polarized light is converted into unpolarized one. An artificial polarization-dependent delay is employed substitute for polarization maintaining fiber, a compact depolarizer for linearly polarized light with any direction of vibration is proposed. Before being depolarized, the incident linearly polarized light is converted into an elliptical polarized light by a quarter-wave plate and is divided into two orthogonal polarized parts always with equal intensity, so that the depolarizer is independent of the optical field direction of incident light. The depolarization performance evolution with the order of quarter-wave plate, center wavelength and optical field direction of incident light is calculated. Low DOP (2.6%), low insertion loss (0.6 dB) and small insertion loss fluctuation (0.11 dB) are obtained for a linearly polarized light with 0.13 nm spectral width. Theoretical analyses and experimental results show that proposed depolarizer has low DOP, low insertion loss and small insertion loss fluctuation, and can be operated in a wide spectral band.