DFB photonic crystal fibre (DFB-PCF) laser in Er3+ doped air-silica structured optical fibre Nathaniel Groothoffa, John Canninga*, Hugh Inglisb, Tom Ryana, Katja Lyytikainena, Justin Digweeda a
Optical Fibre Technology Centre, University of Sydney Australian Photonics Cooperative Research Centre, 206 National Innovation Centre, Australian Technology Park, Sydney NSW 1430, Australia b Redfern Optical Components, Pty Ltd National Innovation Centre, Australian Technology Park, Sydney NSW 1430, Australia
ABSTRACT The construction and operation of a DFB photonic crystal fibre laser produced in Er3+ core doped air-silica structured optical fibre is presented. Its potential in sensing generally is elaborated. Keywords: Photonic crystal fibre, DFB, fibre laser.
1. INTRODUCTION: Recently, we reported the first grating based laser in photonic crystal fibre where the gratings were inscribed directly to produce a short Distributed Bragg Reflector Photonic Crystal Fibre (DBR-PCF) laser1. The ability to avoid using germanate in the core to enhance the photosensitivity, thus using two-photon excitation directly into the band edge of silica2, is of particular benefit in optimising rare earth transitions and avoiding hydrogen loading. In the previous work we measured the gain of our fibre to be 0.32dB/cm at 1533nm1, sufficiently high enough to potentially allow DFB fibre laser action in the doped photonic crystal fibre. In this paper we report fabricating and characterising such a laser – as well as the first demonstration of a DFB laser in photonic crystal fibre, this is to our knowledge the first time that a multi-(two) photon approach directly into the band edge of silica has been used to write a complex grating structure. These lasers are particularly significant because they operate as resonant active cavity detectors with optical fields that can be easily accessed by the measurand of choice placed within the air holes of a photonic crystal fibre. This combination solves ongoing issues in achieving unprecedented sensor performance with existing devices.
2. FIBRE AND GRATING FABRICATION: A number of steps were involved with the fabrication of the air-silica structured Er3+ core doped aluminosilicate optical fibre. Details can found in reference 1. Initially, modified chemical vapour deposition (MCVD) was used to produce a preform with the Er3+ doped core. This was then etched with hydrofluoric acid to remove the outer silica section. The remaining 2mm diameter Er3+ capillary was stacked in the centre of the PCF preform, which was subsequently drawn into a photonic crystal fibre with a doped centre. The diameter of the fibre used in these experiments is 100Pm and supports two modes: a fundamental mode and a higher order mode3.
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17th International Conference on Optical Fibre Sensors, Marc Voet, Reinhardt Willsch, Wolfgang Ecke, Julian Jones, Brian Culshaw, eds., Proceedings of SPIE Vol. 5855 (SPIE, Bellingham, WA, 2005) · 0277-786X/05/$15 · doi: 10.1117/12.623497
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Fabrication of the distributed feedback (DFB) fibre Bragg grating (FBG) involved grating writing directly through an optical phase mask. The laser used was an ArF exciplex laser (wavelength = 193nm, pulse width ~15ns, pulse to pulse fluctuations
