1. L. Di Labio, W. Lüthy, V. Romano, T. Feurer Transitions and mechanisms
Multiply RE-doped single core broadband fibre
L. Di Labio, W. Lüthy, V. Romano, T. Feurer
Institute of Applied Physics, University of Bern, Sidlerstr. 5, 3012 Bern 
F. Sandoz
Silitec Fibers SA, Route de la Gare 70, 2017 Boudry
Abstract A single core fibre doped with five different rare earths, Nd3+, Ho3+, Er3+, Tm3+, and Yb3+, is manufactured with the technique of dry granulated oxides. Under excitation of 804 nm wavelength, fluorescence of the five dopant ions occurs. Excited state absorption and / or energy transfer up-conversion lead to an extremely broad spectrum ranging from 363 nm up to 2300 nm. With an output power of 34 mW and a NA of 0.1, a radiance exceeding 3 kW·sr-1·cm-2 is reached.
Preform
Fabricated with granulated oxides
Mixture
0.1 at. % Nd at. % Ho at. % Er at. % Tm at. % Yb3+ 7 at. % Al3+
Fibre drawing
Preheating at ~1300 °C for 1 h Evacuation and preheating for an additional hour Drawing at approx °C
Fibre
Øcladd = 180 mm, Øcore = 6.5 mm Attenuation: 1.87 dB/m and 1.09 dB/m Radiance: 3.27 kW·sr-1·cm-2
Excitation is performed with an Ar-ion laser pumped Ti:sapphire laser around 800 nm
RE2O3
SiO2
Al2O3
Spectrum
Fluorescence spectrum upon 804 nm excitation. The line with “*” is assigned to a second order peak of the 977 nm Yb3+ emission
Transitions and mechanisms
GSA: ground state absorption; ESA: excited state absorption; ET: energy transfer (donor); ETU: energy transfer up-conversion (donor)
Wavelength
[nm] RE
Assigned
transition
Abs. length
[cm]
Excitation mechanism
363
Tm3+
1D2 → 4H6
4.46
ESA
458
1D2 → 3F4
475
Er3+
Ho3+
1G4 → 3H6
4F7/2 → 4I15/2
5F3 → 5I8
4.44
ETU (Nd3+, Yb3+)
ETU (Yb3+)
522
2H11/2 → 4I15/2
3.81
ESA, ETU (Yb3+)
546
4S3/2 → 4I15/2
(5F4, 5S2) → 5I8
5.01
650
1G4 → 3F4
5F5 → 5I8
4F9/2 → 4I15/2
4.97
ETU (Nd3+)
ESA, ET (Tm3+), ETU (Yb3+)
792
4I9/2 → 4I15/2
4.16
ETU (Yb3+) (?)
890
Nd3+
4F3/2 → 4I15/2
GSA
977
Yb3+
2F7/2 → 2F5/2
8.90
1064
4F3/2 → 4I11/2
8.11
1333
4F3/2 → 4I13/2
7.33
1531
4I13/2 → 4I15/2
7.78
1667
5I5 → 5I7
1803
3F4 → 3H6
7.46
1954
2nd order of 977 nm transition
2120
5I7 → 5I8
7.50
Publications
L. Di Labio, W. Lüthy, V. Romano, F. Sandoz, T. Feurer: ”Broadband emission from a multicore fiber fabricated with granulated oxides”, Applied Optics 47 (10), (2008) L. Di Labio, W. Lüthy, V. Romano, F. Sandoz, T. Feurer: ”Superbroadband fluorescence fiber fabricated with granulated oxides”, Optics Letters 33 (10), (2008)
Acknowledgements
We thank D. Weber for technical assistance. M. Mühlheim, M. Neff, R. Scheidegger and S. Scheidegger we are grateful for their help with fibre drawing. This work was supported in part by the Swiss Commission for the Encouragement of Scientific Research CTI under project NMPP-NM.