Jabir M V, Samanta G K
Photonic Sciences Lab., Physical Research Laboratory, Navarangpura, Ahmedabad, 380009, Gujarat, India.
Sci Rep. 2017 Oct 3;7(1):12613. doi: 10.1038/s41598-017-12709-5.
We report on a compact, simple and robust high brightness entangled photon source at room temperature. Based on a 30-mm-long periodically-poled potassium titanyl phosphate crystal, the source produces non-collinear, type-0, phase-matched, degenerate photons at 810 nm with spectral brightness as high as 0.41 ± 0.02 (0.025 ± 0.02) MHz/mW/nm for multi (single) mode fiber coupling. So far, this is the highest number of degenerate photons generated using a continuous-wave laser pumped bulk crystal and detected using multimode fiber. We have studied the dependence of pump focusing on the brightness of the generated photons collected using both multimode, and single mode fibers. For a fixed pump power and crystal parameters, the SPDC source has an optimum pump waist radius producing maximum number of paired photons. Combining the crystal in a novel system architecture comprised with Sagnac interferometer and polarizing optical elements, the source produces polarization entangled photon states with high spectral brightness. Even in the absence of any phase compensation, the entangled photon states detected using single mode fiber have a Bell's parameter, S = 2.63 ± 0.02, violating the Bell's inequality by nearly 32 standard deviations and fidelity of 0.975. The compact footprint, robust design, and room temperature operation, make our source ideal for various quantum communication experiments.
我们报道了一种紧凑、简单且坚固的室温高亮度纠缠光子源。基于一块30毫米长的周期极化磷酸钛氧钾晶体，该源产生波长为810纳米的非共线、0型、相位匹配的简并光子，对于多模（单模）光纤耦合，其光谱亮度高达约0.41±0.02（约0.025±0.02）兆赫/毫瓦/纳米。到目前为止，这是使用连续波激光泵浦体晶体并通过多模光纤检测到的简并光子的最高数量。我们研究了泵浦聚焦对使用多模和单模光纤收集的产生光子亮度的影响。对于固定的泵浦功率和晶体参数，自发参量下转换（SPDC）源有一个产生最大数量成对光子的最佳泵浦腰半径。将该晶体组合到一个由萨尼亚克干涉仪和偏振光学元件组成的新型系统架构中，该源产生具有高光谱亮度的偏振纠缠光子态。即使在没有任何相位补偿的情况下，使用单模光纤检测到的纠缠光子态的贝尔参数S = 2.63±0.02，违反贝尔不等式近32个标准差，保真度为0.975。紧凑的尺寸、坚固的设计和室温运行，使我们的源成为各种量子通信实验的理想选择。
