关键词: 光子带隙/
电磁诱导透明/
自发辐射相干
English Abstract
Improvement on reflectivity of tunable photonic band gap with spontaneous generated coherence
Yang Liu1,Gao Zhong-Xing1,2,
Xue Bing1,
Zhang Yong-Gang1,
Cai Yong-Mao3
1. College of Automation, Harbin Engineering University, Harbin 150001, China;
2. College of Science, Harbin Engineering University, Harbin 150001, China;
3. School of Science, Northeast Electric Power University, Jilin 132012, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grants Nos. 11747048, 11804066, 61773133), the China Postdoctoral Science Foundation (Grant No. 2018M630337), and the Fundamental Research Funds for the Central Universities, China (Grant No. HEUCFM180401).Received Date:17 July 2018
Accepted Date:28 August 2018
Published Online:05 December 2018
Abstract:The photonic band gap is a spectral range which cannot propagate in a periodic optical nanostructure, that is, the structure itself has a “forbidden band”. It has been successfully applied to the filters, amplifiers, mixers, etc. As is well known, dynamically tunable photonic band gaps in cold atomic lattices are of great importance in various research fields. However, the photonic band gaps of a traditional photonic crystal are non-tunable because the periodic structure is determined once the photonic crystal is grown. On the other hand, a majority of previous researches focused on improving the reflectivity of photonic band gap, which can only keep approaching to 1. Due to the action of the vacuum of the radiation field, near-degenerate lower level has an additional coherence term, the spontaneously generated coherence term. In this paper, we consider a three-level ∧-type atomic system driven by a strong coherent field, a weak coherent field and an incoherent pump, in which the two ground states are of hyperfine structure. The one-dimensional photonic band gaps are formed by cold atoms trapped in a one-dimensional-ordered optical lattice and this system may create two photonic band gaps (PBGs). The trapped cold atoms have a Gaussian density distribution in each period as determined by the optical potential depth and the average atomic temperature. We investigate in detail how the reflectivities of the two PBGs are influenced by the coherent effect of spontaneously generated coherence. Then, we find that the reflectivities of the two band gaps can be significantly improved by the spontaneously generated coherence. The reflectivities of such two band gaps can be dynamically manipulated by varying the intensity of incoherent driving field and the relative phase between the probe field and the coupling field, which cannot be realized in a conventional ∧-type atomic system. Besides, by adjusting the parameters appropriately, the reflectivities of these two band gaps can be higher than 1, which is because probe field gain stems from the spontaneously generated coherence. In the future, photonic transport properties can be investigated in the three-dimensional atomic lattices and this work is meaningful for the optical routing, photodiode and transistor.
Keywords: photonic band gap/
electromagnetically induced transparency/
spontaneously generated coherence
