Study On Properties Of Erbium-doped Fiber For Solid-state Quantum Memory

Solid-state materials doped with rare-earth ions have the characteristics of narrow homogeneous linewidth,long optical coherence time,and large inhomogeneous broadening at the temperature of dilution refrigerator.They are considered as the most potential candidates for solid-state quantum memory.Optical fiber doped with erbium ions has the optical absorption compatible with the telecom-C band,which makes it an important material for providing light-atom interaction in this band.At present,the temperature for investigating the coherent properties of erbium ion in fiber is as low as150 mK.It is an effective way to improve the optical coherence properties of erbium ions by lowering the temperature.In this paper,we placed erium-doped fiber at a temperature of 10 mK to explore the optical coherence properties of erbium ions.The main work includes:1.Based on the dilution refrigerator,a low-temperature quantum optics experimental platform with a temperature as low as 7 mK and magnetic fields up to 7 T was built.A sample winding of erbium-doped fiber with an erbium ion concentration of 200 ppm and a length of 9.5 m was realized,and a low-loss fiber connection from room temperature to low temperature was achieved.The connection loss is 1.9 dB.2.At low temperature,we experimentally measured the optical properties of erbium ions in erbium-doped fiber,including inhomogeneous broadening,transition dipole moment,homogeneous linewidth,and Zeeman sublevel lifetime.The main results are as following:?1?At the temperature of dilution refrigerator,the erbium-doped fiber has an inhomogeneous broadening higher than 1 THz,and its maximum optical depth is 3.24 in1530 nm.?2?We measured the ⁴I_15/2-⁴I_13/2 transition dipole moment of erbium ions in fiber via optical nutation.At a wavelength of 1537 nm and a magnetic field of 1 T,we obtained the maximum transition dipole moment of?3.424±0.019?×10^-32 C·m.?3?By using two-pulse photon echo,we studied the variation of the homogeneous linewidth of erbium ions in fiber with temperature and applied magnetic field.At a temperature of 10 mK and a magnetic field of 1 T,we obtained the narrowest homogeneous linewidth of 3 kHz,and the corresponding optical coherence time is 106?s.?4?By using spectral hole burning,we investigated the dependence of Zeeman sublevel lifetime of erbium ions in fiber on magnetic field.It is found that there are two decoherence processes for Zeeman sublevel in this erbium-doped fiber.At a temperature of 10 mK and a magnetic field of 100 G,the Zeeman sublevel lifetimes corresponding to two processes are 0.524±0.091 s and 13.569±2.760 s,respectively.