We have developed an optical parametric amplification module for quadrature squeezing with input and output ports coupled with optical fibers for both fundamental and second harmonic. The module consists of a periodically poled LiNbO3 ridge waveguide fabricated with dry etching, dichroic beamsplitters, lenses and four optical fiber pigtales. The high durability of the waveguide and the good separation of squeezed light from a pump beam by the dichroic beamsplitter enable us to inject intense continuous-wave pump light with the power of over 300 mW. We perform −4.0±0.1 dB of noise reduction for a vacuum state at 1553.3 nm by using a fiber-optics-based measurement setup, which consists of a fiber-optic beamsplitter and a homemade fiber-receptacle balanced detector. The intrinsic loss of the squeezed vacuum in the module is estimated to be 25%. Excluding the extrinsic loss of the measuremental system, the squeezing level in the output fiber of the module is estimated to be −5.7±0.1 dB. A modularized alignment-free fiber-coupled quadrature squeezer could help to realize quantum information processing with fiber optics.

中文翻译：

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使用光纤耦合 PPLN 脊波导模块进行 4-dB 正交压缩

我们开发了一种用于正交压缩的光学参量放大模块，其输入和输出端口与用于基波和二次谐波的光纤耦合。该模块由周期性极化的 LiNbO3 脊形波导组成，采用干法蚀刻、二向色分束器、透镜和四个光纤尾纤制成。波导的高耐用性和二向色分束器将压缩光与泵浦光束良好分离，使我们能够注入功率超过 300 mW 的强连续波泵浦光。我们使用基于光纤的测量装置对 1553.3 nm 的真空状态进行 -4.0±0.1 dB 的降噪，该装置由光纤分束器和自制的光纤插座平衡检测器组成。模块中压缩真空的固有损失估计为 25%。排除测量系统的外在损耗，模块输出光纤中的压缩电平估计为-5.7±0.1 dB。模块化免对齐光纤耦合正交挤压器有助于实现光纤量子信息处理。