对应于铯原子D1线连续可调谐正交压缩态光场的制备

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,利用两镜连续简并光学参量振荡器中的参量下转换过程,制备出2.8 d B正交压缩真空态光场.然而,所产生光场的压缩度较低,对于对压缩光具有实用意义的可调谐性能也未做进一步探究.理论分析表明,光学参量振荡器后腔镜对信号光透射率的增加及内腔损耗的减小可以提高压缩度.因此,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,降低了光学参量腔阈值,获得压缩度为3.3 d B的单模正交压缩真空光.当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了良好的基础.

Preparation of continuously tunable orthogonal squeezed light filed corresponding to cesium D1 line

The non-classical light resonance 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 a simplified hyperfine structure and can be used to realize a light-atom interface.In our previous work,we demonstrated 2.8-dB quadrature squeezed vacuum light at cesium D₁ line in an optical parametric oscillator(OPO)with a periodically poled KTP(PPKTP)crystal.However,the squeezing level is relatively low,and the tunability that has practical significance for squeezed light has not been further investigated.Theoretically,the increase of the transmittance of output mirror and the decrease of the intra-cavity loss of the OPO can improve the squeezing level.Here,we use super-polished and optimal coating cavity mirrors to improve the nonlinear process in OPO.We prepare 447.3 nm blue light from 894.6 nm fundamental light by a second harmonic generation cavity(SHG).The SHG is a two-mirror standing-wave cavity with a PPKTP crystal as the nonlinear medium.The power of generated blue laser is 32 mW when the incident infrared power is 120 mW.Using the blue light to pump an OPO,we achieve quadrature squeezed vacuum light at cesium D₁ line.The OPO is a two-mirror standing-wave cavity with a PPKTP crystal.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.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 act as an optical parametric amplifier(OPA),and test the tunability of squeezzed light.The blue light and the squeezed light are tuned by using a low-frequency triangular wave signal to scan the Ti:sapphire laser.Gradually increasing the amplitude of the scanning triangle wave signal,the generated bright squeezed light can be continuously tuned over a range around 80 MHz without losing the stability of the whole system.The generated squeezed light offers the possibility for the efficient coupling between the non-classical source and solid medium in the process of quantum interface.