Linear and nonlinear optical properties of the PbSe quantum dots doped germano-silica glass optical fiber Pramod R. Watekar a,b , Seongmin Ju b , Aoxiang Lin c,d , Myoung Jin Kim a , Byeong Ha Lee a , Won-Taek Han a,b, ⁎ a Department of Information and Communications, Gwangju Institute of Science and Technology Oryong-Dong, Buk-Gu, Gwangju, 500-712, Republic of Korea b Graduate Program of Photon Science and Technology, Gwangju Institute of Science and Technology Oryong-Dong, Buk-Gu, Gwangju, 500-712, Republic of Korea c Lehigh University, Bethlehem, PA 18015, United States d State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Xi’an, People's Republic of China abstract article info Available online 9 June 2010 Keywords: Optical fiber; Quantum dots We report development of a new fiber doped with PbSe quantum dots for nonlinear optical applications. PbSe quantum dots related absorption peaks were obtained at 1021, 1093 and 1351 nm. The resonant optical nonlinearity and attenuation at 1500 nm were measured to be 9.4×10 -16 m 2 /W and 0.01 dB/m, respectively. The emission around 1540 nm was observed upon near resonant pumping at 1064 nm. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Recently, glasses and optical fibers doped with semiconductor nanoparticles have been found to possess a large optical nonlinearity and have attracted the scientific attention due to their applications as saturable absorbers for mode-locking and Q-switching of near infra- red lasers, ultrafast signal switches or routers, light converters and possible waveguide amplifiers for telecommunications [1–5]. In order to realize active devices, cluster-matter formed of II–VI semiconductor with a few nanometer size embedded into a dielectric host material, which exhibits strong optical nonlinearity have been widely reported for quantum dots (QDs) of CdSe, CdS, etc., [4,5]. Especially, IV–VI semiconductor QDs of lead chalcogenides such as PbS, PbSe, and PbTe are candidates for optical device applications because of their narrow band-gap, large nonlinearity, and fast response time [6–8]. As compared to II–VI metal monoselenides (ZnSe, CdSe, etc.), the ‘pseudo II-VI’ compound PbSe is a unique material due to its pseudo-divalent p 2 state that gives valance band maximum and conduction band minimum located at the fourfold-degenerate L-point in the Brillouin zone [6]. The emission from PbSe QDs is known to be in the range of the optical communication band (around 1.55 μm). Large optical nonlinearity of PbSe QDs along with its ps response time makes it suitable for optical switching applications. In the current commu- nication, we report the development and linear and nonlinear optical properties of the germane-silica glass optical fiber doped with PbSe QDs. 2. Experiments The alumino-germano-silicate optical fiber preform was fabricated by using the MCVD technique and its core was doubly doped with the acid solution containing Pb and Se (1:1, 5 mg) using a modified solution doping technique. An additional glass layer was deposited after the solution doping and the subsequent drying of soaked preform to reduce the possible evaporation of dopants. The optical fiber was drawn with an outer diameter of 125 μm, a core diameter of 8 μm, and a numerical aperture of 0.13. The spontaneous emission from the PbSe QDs doped optical fiber was measured by pumping with the 1064 nm Nd:YAG laser (Golden Light, GL207) and by collecting the emission at the optical spectrum analyzer (OSA). The Nd:YAG laser had the maximum power of 300 mW at 1064 nm, and its power was coupled into the optical fiber by using a collimator. All experiments were performed at the room temperature and an optical spectrum analyzer (OSA) (Ando AQ6317B) used for measure- ments had a 0.01 nm spectral resolution, a broadband amplified spontaneous emission light source (ASE, Thorlabs, SOA240) had peak intensity at 1.53 μm. 3. Determination of the resonant optical nonlinearity To measure the resonant optical nonlinearity of the PbSe QDs- doped optical fiber, the pump laser at 1064 nm and the signal light (1400 nm–1650 nm) were simultaneously launched into the fiber by using a coupler as shown in Fig. 1. Resulting interference pattern were recorded using the OSA [2,9]. The resonant optical nonlinearity n 2 , the effective length L eff , and the effective area A eff of PbSe QDs-doped fiber were calculated by Eqs. (1), (2) and (4), respectively: n 2 = A eff λ p Δλ L eff ð2bÞP p S ð1Þ Journal of Non-Crystalline Solids 356 (2010) 2384–2388 ⁎ Corresponding author. Tel.: + 82 62 970 2214; fax: + 82 62 970 2204. E-mail address: wthan@gist.ac.kr (W.-T. Han). 0022-3093/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2010.02.012 Contents lists available at ScienceDirect Journal of Non-Crystalline Solids journal homepage: www.elsevier.com/ locate/ jnoncrysol