TAILIEUCHUNG - Controlling optical bistability in a five-level cascade eit medium
Optical bistability (OB) of an electromagnetically induced transparency (EIT) medium placed in a conventional unidirectional ring cavity is investigated numerically. The medium is excited by a coupling and probe laser lights via a five-level cascade scheme. It is shown that optical bistabe states with controllable switching threshold intensities and width are established simultaneously in three spectral regions corresponding to EIT windows. The current numerical result is compared to a previous analytical result showing influence of coherence terms neglected in the analytical model. | Communications in Physics, Vol. 26, No. 1 (2016), pp. 33-42 DOI: CONTROLLING OPTICAL BISTABILITY IN A FIVE-LEVEL CASCADE EIT MEDIUM PHAN VAN THUAN, TA TRAM ANH, LE CANH TRUNG, NGUYEN TIEN DUNG, LUONG THI YEN NGA, DINH XUAN KHOA, LE VAN DOAI, AND NGUYEN HUY BANG† Vinh University, 182 Le Duan Street, Vinh City, Vietnam NGUYEN VAN AI Ky Lam High School, Ky Anh district, Ha Tinh province, Vietnam † E-mail: bangnh@ Received 19 April 2016 Accepted for publication 01 June 2016 Abstract. Optical bistability (OB) of an electromagnetically induced transparency (EIT) medium placed in a conventional unidirectional ring cavity is investigated numerically. The medium is excited by a coupling and probe laser lights via a five-level cascade scheme. It is shown that optical bistabe states with controllable switching threshold intensities and width are established simultaneously in three spectral regions corresponding to EIT windows. The current numerical result is compared to a previous analytical result showing influence of coherence terms neglected in the analytical model. Keywords: optical bistability, electromagnetically induced transparency, coherent optical effects. Classification numbers: . I. INTRODUTION In the last three decades, we have witnessed a remarkable progress in OB research due to its potential applications in both optical sciences and photonic technology such as all-optical switches, all-optical memories, optical transistors, and all-optical logic gates and processors. In the early years of the OB research using atomic media, a great interest was focused on twolevel atomic media [1–3]. It had been shown that bistable states can be established for certain values of input intensity [2, 3]. Although the usual OB behaviors of the two-level atomic system were observed experimentally, relevant applications are still limited because only one optical field was employed for both applying and switching, thereby lack of
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