Tong Hoang Tuan
Toyota Technological Institute, Japan
Title: Suppressing 1.06-μm spontaneous emission of Neodymium ions using a novel tellurite all-solid photonic bandgap fiber
Biography
Biography: Tong Hoang Tuan
Abstract
In recent years, the development of high capacity and broad transmission optical systems and devices for global telecommunication networks is rapidly increasing due to the explosive spread of telecommunication devices such as smartphones and computers. Along with the development of broadband optical systems, the demand for optical amplifiers at many diff erent wavelengths in the telecommunication range are also growing. Although Erbium-doped fiber amplifiers (EDFA) are widely used as gain media for wavelength division multiplexing (WDM) systems, their gain bandwidths are as narrow as 30nm from 1530 to 1560nm. In a nearby wavelength range, optical fi ber amplifiers operating near 1.3μm in the telecommunication band where conventional single-mode fi bers have low-loss and low dispersion are very attractive. Among several active rare-earth ions that have been investigated for optical fiber amplifi ers operating near the 1.3μm spectral region, Nd3+ is a potential candidate for compact and highly effi cient optical fi ber amplifi ers even with a short fi ber length of a few centimeters due to its 4F3/2→4I13/2 transition. However, the use of the 1.3μm emission in a practical Nd3+-doped fi ber has faced with several problems. One of its major problems is the presence of competing amplifi ed spontaneous emission (ASE) at 1.06μm due to the 4F3/2→4I11/2 transition whose branching ratio is about 5 times larger than that at 1.3μm. In order to realize a practical optical amplifi er device at 1.3μm, the ASE at 1.06μm must be fi ltered out. In this work, we propose a tellurite all-solid photonic bandgap fi ber (ASPBGF) to fi lter out the competing emission at 1.06μm which is most prominent in the emission spectrum of the Nd3+ ion. A novel Nd3+-doped tellurite ASPBGF is fabricated by using our developed tellurite glasses which have high compatibility of thermal properties and their refractive index diff erence is 0.096 at 1320nm. The fiber is designed with 4 layers of high-index rods to have low confi nement loss. Th e measured transmission spectrum of a 2.2cm long section of the fabricated fi ber exhibits high transmission bands near 0.75 and 1.33μm (about -20dB and -19dB) and a low transmission band in the vicinity of 1.06μm which is about -27dB. By using our fabricated Nd3+-doped tellurite ASPBGF, it is demonstrated for the fi rst time that the 1.06μm emission peak due to the 4F3/2→4I 11/2 transition of Nd3+ ions is greatly suppressed about 12 times as compared to that obtained by using a bulk samples with the same doping concentration.