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Ytterbium doped tantalum pentoxide nanowire waveguide lasers

Ytterbium doped tantalum pentoxide nanowire waveguide lasers
Ytterbium doped tantalum pentoxide nanowire waveguide lasers
Ytterbium (Yb) has been widely studied in several host materials and device forms due to its broad gain bandwidth, long excited-state lifetime, and simple quasi-three energy level structure. Yb doped tantalum pentoxide (Yb:Ta2O5) waveguides are favorable for laser applications since Ta2O5 has promising optical properties including high refractive index (≈2.1), wide transmission spectrum (350 nm to 9 μm) and suitability to host rare-earth ions. In this work, a nanowire waveguide design with taper and coupler section was demonstrated. Thin Yb:Ta2O5 films were fabricated by plasma assisted reactive magnetron sputtering (PARMS) from high purity (99.999%) Ta metal and Yb metal targets at low temperature (< 70°C). The PARMS process allows Yb doping concentration to be easily adjusted, leading to a new flexible deposition method for not only Yb:Ta2O5 but other doped materials. Nanoscale waveguide fabrication processes of strip loaded and buried channel waveguides on SiO2 using electron beam lithography and inductively couple plasma reactive ion etching (RIE-ICP) were demonstrated and the first Yb:Ta2O5 anisotropic RIE-ICP etching process was developed. Buried channel waveguide in polymer fabricated by nano-imprint was also demonstrated, offering low-cost and mass production of nanoscale waveguide. A 6.7 mm long strip loaded Yb:Ta2O5 nanowire waveguide laser with 1.25 atomic percentage Yb doping concentration was demonstrated with a laser cavity formed of bare polished end facets only, with 12% Fresnel reflectivity. Single mode lasing was observed between 1015 nm and 1030 nm in strip loaded waveguides with nanowire of 400 nm width when end pumped by a 977 nm laser diode. The launched power threshold and the slope efficiency were measured to be ≈ 12 mW and ≈ 38%. The lasing wavelength of such waveguide can be switched by tuning the pump coupling position at the coupler section, implying a potential tuning mechanism.The results presented in this work demonstrate the capability of Yb:Ta2O5 for being a waveguide laser, show the great potential for being used in mass-producible, CMOS compatible integrated optical circuits.
University of Southampton
Yan, Xingzhao
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Yan, Xingzhao
320b9089-1fb3-485a-8c1f-45fb1f86efa0
Charlton, Martin
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Pearce, Stuart J
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De Groot, Cornelis
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Morgan, Katrina
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Huang, Ruomeng
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Ye, Sheng
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Yan, Xingzhao (2017) Ytterbium doped tantalum pentoxide nanowire waveguide lasers. University of Southampton, Doctoral Thesis, 172pp.

Record type: Thesis (Doctoral)

Abstract

Ytterbium (Yb) has been widely studied in several host materials and device forms due to its broad gain bandwidth, long excited-state lifetime, and simple quasi-three energy level structure. Yb doped tantalum pentoxide (Yb:Ta2O5) waveguides are favorable for laser applications since Ta2O5 has promising optical properties including high refractive index (≈2.1), wide transmission spectrum (350 nm to 9 μm) and suitability to host rare-earth ions. In this work, a nanowire waveguide design with taper and coupler section was demonstrated. Thin Yb:Ta2O5 films were fabricated by plasma assisted reactive magnetron sputtering (PARMS) from high purity (99.999%) Ta metal and Yb metal targets at low temperature (< 70°C). The PARMS process allows Yb doping concentration to be easily adjusted, leading to a new flexible deposition method for not only Yb:Ta2O5 but other doped materials. Nanoscale waveguide fabrication processes of strip loaded and buried channel waveguides on SiO2 using electron beam lithography and inductively couple plasma reactive ion etching (RIE-ICP) were demonstrated and the first Yb:Ta2O5 anisotropic RIE-ICP etching process was developed. Buried channel waveguide in polymer fabricated by nano-imprint was also demonstrated, offering low-cost and mass production of nanoscale waveguide. A 6.7 mm long strip loaded Yb:Ta2O5 nanowire waveguide laser with 1.25 atomic percentage Yb doping concentration was demonstrated with a laser cavity formed of bare polished end facets only, with 12% Fresnel reflectivity. Single mode lasing was observed between 1015 nm and 1030 nm in strip loaded waveguides with nanowire of 400 nm width when end pumped by a 977 nm laser diode. The launched power threshold and the slope efficiency were measured to be ≈ 12 mW and ≈ 38%. The lasing wavelength of such waveguide can be switched by tuning the pump coupling position at the coupler section, implying a potential tuning mechanism.The results presented in this work demonstrate the capability of Yb:Ta2O5 for being a waveguide laser, show the great potential for being used in mass-producible, CMOS compatible integrated optical circuits.

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Published date: June 2017

Identifiers

Local EPrints ID: 424429
URI: http://eprints.soton.ac.uk/id/eprint/424429
PURE UUID: e433a694-cc1d-46a9-8758-09bc019f1d8d
ORCID for Cornelis De Groot: ORCID iD orcid.org/0000-0002-3850-7101
ORCID for Katrina Morgan: ORCID iD orcid.org/0000-0002-8600-4322

Catalogue record

Date deposited: 05 Oct 2018 11:37
Last modified: 30 Jan 2020 05:15

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