Preparation of Yb 3+ -doped Silica-based Glass for High Power Laser Applications ChangMing Xia College of Information Science and Engineering Yanshan University Qinhuangdao, China e-mail: xiacmm@126.com Ying Han College of Information Science and Engineering Yanshan University Qinhuangdao, China e-mail: lucyhan2004@126.com GuiYao Zhou, LanTian Hou College of Information Science and Engineering Yanshan University State Key Laboratory of Metastable Materials Science & Technology, Yanshan University Qinhuangdao, China e-mail: zguiyao@163.com, hlt8068853@163.com Abstract—We demonstrate a novel method for preparing bulk Yb 3+ -doped fused silica glass for high power laser by solution doping and high temperature melting technique. The silica glass with high Yb 3+ concentration (5.34 × 10 20 ions/cm 3 ) is prepared. The absorption and fluorescence emission spectra of Yb 3+ ions in the silica glass are recorded. Experiment results show that this glass prepared by this novel method has two strong absorption peaks at wavelength of 918 nm and 976 nm, which is suitable for diode laser pumping. Emission spectrum shows the wide emission bands extending from 900 to 1100 nm, and it has a broadband emission spectrum at wavelength of 1014 nm using model Mira 900F Ti-sapphire system as pump source. There is no thermal damage when the laser pump power is up to 100 W. Therefore, this glass is of interest as a new potential laser material serving as the core of photonic crystal fibers (PCF) for high power fiber laser applications. Keywords- photonic crystal fiber laser;Yb 3+ -doped silica glass; solution doping method I. INTRODUCTION Recently, high power fiber laser (HPFL) has attracted more and more attention due to its more compact and high efficiency [1]. For HPFL, there are many important applications in defense, industrial material processing, remote sensing, surgery, biological imaging and so on. Rare Earth (RE)-doped large mode field area photonic crystal fibers (PCF) [2-5] are well suited for the application in HPFL, especially, Yb 3+ -doped large mode area PCF is very attractive. Ytterbium ions, a two energy level system, exhibit not only a large absorption cross-section but also a broad absorption band between 800 and 1100 nm. Ytterbium (Yb) is seen as the main rare earth dopant for high power diode pumped laser and wavelength-tunable solid-state laser systems because of its advantages such as the high efficiency, high beam quality, broad absorption band and broad emission band [6]. For HPFL, the RE ions concentration in the host glasses must be as high as possible to ensure sufficient gain despite of short active length of HPFL, which helps to suppress nonlinear effect such as Stimulated Raman Scattering(SRS) and Stimulated Brillouin Scattering(SBS) [7-8]. At present, the interesting work is to fabricate this kind of optical-grade glass with high Yb 3+ -doped concentration, low loss and high optical gain efficiency. Silica glass is the most common host material for manufacturing optical fibers, although other host material is also the subject of investigation. Silica has received some attentions for the host material of the Yb 3+ -doped glass, because the silica glass [9] has high transparency from ultraviolet to near infrared and high glass transition temperature for HPFL applications. However, there are many problems to be solved for fabricating the active silica glass serving as the core of PCF. Modified Chemical Vapor Deposition (MCVD) method [10- 13] is commonly used process to produce Yb 3+ -doped optical fiber because of its relative accurate control, but the cost of produce is very high. Other popular processes for making the active glass include Outside Vapor Deposition (OVD) [14] and Vapor Axial Deposition (VAD) [15]. However, they have some limitations on the glass size and RE-doped concentration. It is very difficult to remove the outer silica cladding of RE-doped silica glass prepared by MCVD. In this paper, we demonstrated a novel preparing technique of active optical silica glass based on the solution deposition, which has many advantages, such as allowing high incorporation of dopants and the fabrication of the bulk RE- doped silica glass, and accurately controlling dopant concentration. The silica-based glass with high Yb 3+ concentration is prepared by this novel method. Spectroscopic properties and laser performances of the glass are investigated. II. EXPERIMENT Yb 3+ -doped silica powder can be obtained by the following processes: firstly, the alcoholic solution is composed of AlCl 3 , YbCl 3 , KCl and the high purity (6N) silica powder (mole ratio of 2.009%, 0.221%, 0.448%, 97.322%, respectively). Al 3+ prevents rare earth ions from clustering and raises the core’s index of refraction to facilitate guiding of light [16], and co-doped with 10 at% alumina is the recommended amount for best fluorescence lifetime [17]. Besides reduction of clustering problem, Al 3+ is preferred since Al 3+ addition broadens the RE emission spectra [18], allows to achieve the desired RE concentration