Broadband visible-to-NIR ASE from Bismuth doped optical fibers: a window towards lasing

Abstract

We report broadband ASE within 650–825 nm, peaking at 655, 680, 715 nm, from Bismuth (Bi) doped optical fibers (BDFs) under 533 nm core-pumping excitation technique; 715 nm peak was prominent among others. Fiber preforms were fabricated through MCVD process associated with solution doping technique using Bi-,Yttrium/Lithium co-doped phosphosilicate, germanosilicate glasses (BYPS/BYGS/BLGS) as core materials. Optimum fiber lengths providing maximum ASE were 15 cm for BYPS and 35 cm for BYGS fibers. Possible issues behind strong ASE without any lasing were demonstrated using modal analysis of BDFs at 533 and 715 nm. This study is a step towards developing visible-to-NIR laser using BDFs of such types.

Effects of Electron Irradiation on Optical Properties of Bismuth-Doped Phosphosilicate Fiber

“…Such pump level was chosen, on the one hand, to provide population inversion in the system of BACs sufficient to get pronounced PL power and, on the other hand, to guarantee safety of registration with OSA. As seen, BYP fiber demonstrates pronounced PL in VIS/NIR, characteristic to BACs in phosphosilicate fibers [1,[11][12][13] with maximum at ~1200-1300 nm slightly depending on the excitation wavelength. Say, when pumped at 405 nm, BYP fiber demonstrates the PL bands centered at 760 and 1280 nm.…”

“…The basic waveguide properties of the fiber, viz., numerical aperture (NA), ~0.11; core diameter, ~4.42 μm; and refractive-index (RI) difference, ~0.004, were managed to fulfill single-mode propagation of light beyond ~600 nm, which is potentially perspective for amplifying/lasing in VIS/NIR [13].…”

“…The spectrally dependent IA in the fiber can be explained likewise that in β-irradiated aluminosilicate BDFs [1,2], its rise in VIS seemingly originates from extra Bi/P BACs generated, while its gravity center shift toward UV is related to growth of P-centers. Besides, possible contribution in the latter trend may stem from growth of RS (yet occurring in pristine BYP fiber; see [13]) due to irradiation-induced nanoscale degradation of core glass. However, given that IA spectra of irradiated BYP fiber are essentially structureless, it is nearly impossible to separate the evoked mechanisms.…”

“…In this chapter, we present a review of our recent studies of the basic material and optical properties of a homemade Bi-doped yttrium-phosphosilicate (BYP) fiber in pristine state [11][12][13] and after irradiating by a beam of β-electrons [14]. The review's main scopes are dose-induced transformations in absorptive, emissive, and waveguide characteristics of the fiber.…”