Advances in Optics, Photonics, Spectroscopy & Applications <strong>VI</strong> <strong>ISSN</strong> <strong>1859</strong> - <strong>4271</strong>Dao Duy Tha<strong>ng</strong>, Nguyen Dinh Hoa<strong>ng</strong>, Phu<strong>ng</strong> Viet Tiep, Nguyen T. Thanh Bao,Vu Thi Bich, Nghiem T. Ha Lien, Nguyen Thanh Binh, Dinh Van Tru<strong>ng</strong>NHỮNG NGHIÊN CỨU VÀ PHÁT TRIỂN PHÉP ĐO ĐỘ DÀI CỦA XUNG LASER CỰC NGẮNBẰNG THIẾT BỊ TỰ TƯƠNG QUAN................................................................................................751Vuo<strong>ng</strong> Van Cuo<strong>ng</strong>, Do Quoc Khanh, Nguyen Van Hao, Nguyen Dai Hu<strong>ng</strong>TÍNH TOÁN THIẾT KẾ VẬT KÍNH GƯƠNG - THẤU KÍNH CỦA HỆ THỐNG QUANG HỌC ĐẦUTỰ DẪN .............................................................................................................................................758Ha Nguyen BinhCHUYỂN BƯỚC SÓNG BẰNG HIỆU ỨNG TRỘN BỐN SÓNG PHÂN BỐ GAUSS TRONGKHUẾCH ĐẠI QUANG BÁN DẪN (SOA) ........................................................................................766Tran Ba Chu, Nguyen Tro<strong>ng</strong> Tuan, Chu Van Lanh và Le Ngoc AnhAUTHOR INDEX ...............................................................................................................................77312
Nhữ<strong>ng</strong> tiến bộ <stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>> <stro<strong>ng</strong>>Qua<strong>ng</strong></stro<strong>ng</strong>> học, <stro<strong>ng</strong>>Qua<strong>ng</strong></stro<strong>ng</strong>> <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>ổ và Ứ<strong>ng</strong> dụ<strong>ng</strong> <strong>VI</strong> <strong>ISSN</strong> <strong>1859</strong> - <strong>4271</strong>MANIPULATING SINGLE ATOMS AND PHOTONSUSING OPTICAL NANOFIBERSKohzo HakutaCenter for Photonic Innovations and Department of E<strong>ng</strong>ineeri<strong>ng</strong> ScienceUEC Tokyo, The University of Electro-CommunicationsChofu, Tokyo 182-8585, JapanFax: 81-42-443-5507, e-mail: hakuta@pc.uec.ac.jpAbstract. We discuss how optical nanofibers, subwavele<strong>ng</strong>th-diameter fibers, can open newperspectives in quantum optical technologies theoretically and experimentally. Discussions are mainlyfocused on the manipulation of spontaneous emission for atoms around the nanofiber. We show that<stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons from si<strong>ng</strong>le quantum emitters can be efficiently channeled into guided modes of thenanofiber. Especially by fabrica<s<stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>>>tin</s<stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>>>g a cavity structure o the nanofiber, the channeli<strong>ng</strong> efficiency can beimproved to exceed 80 % although the cavity finesse is moderate. We discuss also how to realize sucha nanofiber cavity experimentally.Keywords: nanofiber, si<strong>ng</strong>le-<stro<strong>ng</strong>>ph</stro<strong>ng</strong>>oton generation, quantum optics.I. INTRODUCTIONThe progress of modern quantum optics has opened a door to a new type of technology,which is known as quantum information technology. The technology is expected to grow up as anew type of information technology in the comi<strong>ng</strong> decades via the methods of quantumcommunication and/or quantum compu<s<stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>>>tin</s<stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>>>g. One of the key issues of such technology is how tomanipulate si<strong>ng</strong>le atoms and <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons, since quantum informations are carried not by coherentlight but by deterministic flow of si<strong>ng</strong>le <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons and/or twin <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons. In this context, variousmethods to manipulate si<strong>ng</strong>le atoms and si<strong>ng</strong>le <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons have been proposed and demonstrated sofar. Examples would include ultra-high finesse cavity with si<strong>ng</strong>le atoms [1], semiconductormicro-pillar with quantum dots [2], and silver nanowire with quantum dots [3].In the present work, we show that subwavele<strong>ng</strong>th fibers, termed optical nanofibers, may opena new route to manipulate si<strong>ng</strong>le atoms and si<strong>ng</strong>le <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons. We discuss usi<strong>ng</strong> optical nanofibershow small number of atoms can be observed, and how spontaneous emission of atoms can bemanipulated. Moreover, we show theoretically that the emitted <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons can be channeled into theguided modes of the fiber with efficiency greater than 80 % by fabrica<s<stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>>>tin</s<stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>>>g cavity structure with amoderate finesse on nanofibers. We discuss a technology to create such cavity structure onnanofibers.II. SPONTANEOUS EMISSION OF “ATOMS” AROUND A NANOFIBERFigure 1(a) shows the conceptual diagram of the present optical nanofiber scheme. Thenanofiber locates at the mid of a tapered optical fiber which satisfies the adiabatic taperi<strong>ng</strong>condition so that the si<strong>ng</strong>le-mode propagation can be maintained for the whole fiber le<strong>ng</strong>th.Atoms distribute in the vicinity of the nanofiber. Since mode density is s<stro<strong>ng</strong>>tro<strong>ng</strong></stro<strong>ng</strong>>ly confined aroundthe nanofaiber, spontaneous emission of atoms around the nanofiber may be very different fromthat for atoms in the free space; that is, appreciable amount of fluorescence <stro<strong>ng</strong>>ph</stro<strong>ng</strong>>otons are emittedinto the guided mode of the nanofiber. Figure 1(b) shows theoretical results for the coupli<strong>ng</strong>13
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