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铯原子D1 线的非经典光由于其波长接近于量子点的独特优势, 在固态量子信息网络的发展中有着重要的应用前景. 在之前的工作中, 将波长锁定于铯原子D1 线的连续钛宝石激光器输出的894.6 nm 红外激光通过外腔倍频产生447.3 nm 蓝光, 抽运由周期极化磷酸氧钛钾晶体构成的连续简并光学参量振荡器, 获得2.8 dB正交压缩真空态光场. 本文在该研究基础上, 通过使用高光洁度腔镜及优化腔镜镀膜参数等方式对光学参量振荡器进行改良, 将阈值降为28 mW, 输出单模正交压缩真空光的压缩度提高至3.3 dB. 当注入信号光使光学参量腔运转为参量反放大状态时, 在系统稳定运行的情况下, 制备的明亮压缩态光场能够连续调谐80 MHz, 为其在量子信息网络中的应用奠定良好基础.The non-classical light resonant on the cesium D1 (894.6 nm) line has important applications in solid-state quantum information networks due to its unique advantages. The cesium D1 line has the merit of simplified hyperfine structure for experimental realization of a light-atom interface. It also lies well within the wavelength regime of excitonic transition in InAs/GaAs quantum dots for integrated quantum interfaces between light and solid-state systems. We prepare the vacuum squeezed light at cesium D1 line with continuous-wave quasi-phase-matching degenerate optical parametric oscillator (OPO), which is pumped by 447.3 nm blue laser generated via frequency doubling of 894.6 nm laser at cesium D1 line. The SHG cavity is a two-mirror standing-wave cavity with a PPKTP crystal as the nonlinear medium. The input coupler has a transmissivity of 5% at 894.6 nm and is highly reflecting at 447.3 nm, while the output coupler is highly reflecting at 894.6 nm and has a transmissivity of 95% at 447.3 nm. The power of generated blue laser is 32 mW when the incident infrared power is 120 mW. In our previous work, we demonstrated 2.8 dB quadrature squeezed vacuum light at cesium D1 line in an OPO with a periodically poled KTP (PPKTP) crystal. Here, we use super-polished and optimal coating cavity mirrors to improve the nonlinear process in OPO. The OPO is a two-mirrors standing-wave cavity with a PPKTP crystal. The input coupler has a transmissivity of 10% at 447.3 nm and is highly reflecting at 894.6 nm, while the output coupler is highly reflecting at 447.3 nm and has a transmissivity of 9.5% at 894.6 nm. The threshold of OPO is reduced to 28 mW. The squeezing level of generated quadrature squeezed vacuum light is increased to 3.3 dB when the pump power is 15 mW. The spectrum analyzer is setting on zero-span mode at 1 MHz. The resolution bandwidth is 30 kHz and the video bandwidth is 100 Hz. Taking into account the overall detection efficiency, the actual squeezing reaches 5.5 dB. We inject a weak signal beam into the OPO cavity to run it as an optical parametric amplifier (OPA), the generated bright squeezed light can be continuously tuned over a range around 80 MHz across D1 line of cesium, offering the possibility for the efficient coupling between the non-classical source and solid medium in the process of quantum interface.
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Keywords:
- nonlinear optics /
- quadrature squeezed light field /
- continuously tunable /
- cesium D1 line
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