Refractive index and low dispersion properties of new fluorophosphate glasses highly doped with rare-earth ions
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A. Margaryan and A. Margaryan AFO Research Inc., Glendale, California 91209 (Received 10 September 2004; accepted 28 October 2004)
A new series of 0.4MgF2–0.4BaF2–0.1Ba(PO3)2–0.1Al(PO3)3 glasses highly doped with rare-earth dopants (RE; Nd2O3, Er2O3, and Yb2O3) have been successfully developed for laser applications. Linear refractive index, dispersion properties including Abbe number (), dispersion parameter (A⬘, B⬘), electronic osciallator energy (Eo), and electronic osciallator strength (Ed) were determined as a function of RE dopants. The refractive index (nD=1.5872 to 1.6047) was found to linearly increase with dopant concentrations irrespective of types of rare earth dopants, while the Abbe number ( ⳱ 65.7 to 68.8) and dispersion parameters including A⬘ (∼62), B⬘, Eo (13 ± 0.5 eV), and Ed (19 ± 1 eV) exhibit a concentration independence. It is remarkable that the refractive index of those new glasses increased with increasing RE dopant concentration, while the relatively large Abbe number of those glasses was independent of dopant concentration. The dependence of refractive index (n) on RE cations with high polarizabilities are discussed in terms of molar volume (Vm) and molar refractivity (Rm). Electronic oscillator strengths (Ed), the average electronic energy gap (Eo), and their respective dependence on RE dopant concentration were also investigated using linear refractive index (n) and Abbe number (). Those results suggest the present new series of glasses are strong candidates for stable laser hosts with extremely low dispersion.
I. INTRODUCTION
Because of a favorable combination of low nonlinear refractive index due to fluoride and high emission cross section due to phosphate, fluorophosphates glass represents one of the best potential rare earth dopant hosts for laser applications.1–4 It was also observed that neodymium-doped fluorophosphate glasses can deliver relatively shorter pulses than pure phosphate glasses, which are attributed to the relatively higher degree of inhomogeneous line broadening in fluorophosphate glasses.5 Other spectroscopic studies have indicated that the fluorophosphate glass doped with erbium is an excellent candidate for broadband amplifiers in the eyesafe region around 1.5 m for applications in communication, medicine, and meteorology.6–10 The attention to ytterbiumdoped fluorophosphate glasses has been devoted to infrared laser applications and the next generation of high Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/JMR.2005.0033 264
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J. Mater. Res., Vol. 20, No. 1, Jan 2005 Downloaded: 08 Jul 2014
energy lasers.11,12 Therefore, fluorophosphate glasses doped with several rare-earth (RE) dopants (Nd2O3, Er2O3, and Yb2O3) have been attractive as host candidates for active as well as passive optical devices. For complete laser applications such as compact fiber lasers and amplifiers, the dependence of refractive index (n) and dispersion properties on RE cations with high polizab
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