Ultra-broadband emission in Er 3+ /Tm 3+ /Ho 3+ triply-doped germanate glass and double-clad optical fiber

Abstract

In this paper 1400 nm–2200 nm broadband emission under 808 nm and 976 nm laser diodes excitation in germanate glasses co-doped with (0.35–0.7) Er 2 O 3 /(0.35–0.7) Tm 2 O 3 /(0–0.15) Ho 2 O 3 (mol%) are presented. Flattened luminescence profiles were achieved as a result of RE content optimization in glasses co-doped with 0.35Er 2 O 3 /0.7Tm 2 O 3 /0.15Ho 2 O 3 , (λ exc = 808 nm) and 0.7Er 2 O 3 /0.35Tm 2 O 3 /0.07Ho 2 O 3 , (λ exc = 976 nm). The second, glass characterized by the widest emission range, has been used for the fabrication of double-clad optical fiber with 15 µm/250 µm (core/outer cladding) diameters. The optimization of broadband spectrum in glass and optical fiber was performed as the result of the superposition of 1550 nm (Er 3+ : 4 I 13/2 → 4 I 15/2 ), 1800 nm (Tm 3+ : 3 F 4 → 3 H 6 ), and 2000 nm (Ho 3+ : 5 I 7 → 5 I 8 ) emission bands. The influence of optical fiber length and pump wavelength on near-infrared amplified spontaneous emission (ASE) features have been determined. As a result, the broadest bandwidth of ASE (415 nm - 3 dB and 731 nm – 10 dB) was obtained in 5 m length optical fiber under 808 nm pumping. It is significantly broader than in silica and tellurite fibers, which showed the advantage of RE triply-doped germanate optical fiber.