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15W diode-pumped Tm:YAG double-clad waveguide laser

15W diode-pumped Tm:YAG double-clad waveguide laser
15W diode-pumped Tm:YAG double-clad waveguide laser
Laser sources with wavelengths around 2µm are of interest for medical, commercial, and remote sensing applications. Typically, high average powers coupled with good beam quality are also desirable for these applications. Diode-pumped planar waveguides are an attractive solution for efficient and compact lasers, with excellent thermal properties and good prospects for power scaling due to their slab geometry [1]. Here, we present results for a planar direct-bonded double-clad waveguide, with a Tm:YAG core, un-doped YAG inner cladding, and sapphire outer cladding layers. The YAG/sapphire numerical aperture is sufficient to contain the highly divergent radiation of a laser diode, allowing a side-pumped arrangement with two proximity-coupled lambda(p)=785nm 20W diode bars, as shown in figure 1. Thus we obtain efficient pumping in a very simple and compact configuration. The thin waveguide dimensions lead to a high pumping intensity, as required for efficient operation of quasi-three level laser systems. Pumping from both sides of the waveguide is also useful in producing a relatively uniform gain distribution. Mirrors were directly coated onto the end faces of the waveguide structure, forming a plane-plane resonator with 10% output coupling.

Figure 1 Proximity-coupled, diode-pumped, double-clad Tm:YAG waveguide

In Tm:YAG cross relaxation processes enable the quantum yield to approach 2, i.e. 2 laser photons for one pump photon. Thus slope efficiencies greater than the Stokes efficiency v(l)/v(p)=0.39 are possible. For 44W of pump power we obtained 15W at 2.02µm, corresponding to an optical to optical efficiency of 34% and a slope efficiency of 61% with respect to absorbed power. The beam quality of the waveguide laser was diffraction-limited in the guided axis due to gain selection of the fundamental mode from the multimode double-clad structure'. However, the 5mm wide gain region in the unguided plane led to a highly multimode output in this axis. The prospects for further power scaling and improved beam quality will be discussed.
Mackenzie, J.I.
1d82c826-fdbf-425b-ac04-be43ccf12008
Mitchell, S.C.
5b900f44-98e4-41e3-98c3-81b75dc68dfe
Beach, R.J.
2f66046b-92c5-472c-ac8d-660bdfddc0e7
Meissner, H.E.
86601686-f210-488c-8261-910cb1ff06a6
Shepherd, D.P.
9fdd51c4-39d6-41b3-9021-4c033c2f4ead
Mackenzie, J.I.
1d82c826-fdbf-425b-ac04-be43ccf12008
Mitchell, S.C.
5b900f44-98e4-41e3-98c3-81b75dc68dfe
Beach, R.J.
2f66046b-92c5-472c-ac8d-660bdfddc0e7
Meissner, H.E.
86601686-f210-488c-8261-910cb1ff06a6
Shepherd, D.P.
9fdd51c4-39d6-41b3-9021-4c033c2f4ead

Mackenzie, J.I., Mitchell, S.C., Beach, R.J., Meissner, H.E. and Shepherd, D.P. (2001) 15W diode-pumped Tm:YAG double-clad waveguide laser. QEP-15: 15th Biennial Meeting of the Institute of Physics Quantum Electronics and Photonics Group, United Kingdom. 03 - 06 Sep 2001. 1 pp .

Record type: Conference or Workshop Item (Poster)

Abstract

Laser sources with wavelengths around 2µm are of interest for medical, commercial, and remote sensing applications. Typically, high average powers coupled with good beam quality are also desirable for these applications. Diode-pumped planar waveguides are an attractive solution for efficient and compact lasers, with excellent thermal properties and good prospects for power scaling due to their slab geometry [1]. Here, we present results for a planar direct-bonded double-clad waveguide, with a Tm:YAG core, un-doped YAG inner cladding, and sapphire outer cladding layers. The YAG/sapphire numerical aperture is sufficient to contain the highly divergent radiation of a laser diode, allowing a side-pumped arrangement with two proximity-coupled lambda(p)=785nm 20W diode bars, as shown in figure 1. Thus we obtain efficient pumping in a very simple and compact configuration. The thin waveguide dimensions lead to a high pumping intensity, as required for efficient operation of quasi-three level laser systems. Pumping from both sides of the waveguide is also useful in producing a relatively uniform gain distribution. Mirrors were directly coated onto the end faces of the waveguide structure, forming a plane-plane resonator with 10% output coupling.

Figure 1 Proximity-coupled, diode-pumped, double-clad Tm:YAG waveguide

In Tm:YAG cross relaxation processes enable the quantum yield to approach 2, i.e. 2 laser photons for one pump photon. Thus slope efficiencies greater than the Stokes efficiency v(l)/v(p)=0.39 are possible. For 44W of pump power we obtained 15W at 2.02µm, corresponding to an optical to optical efficiency of 34% and a slope efficiency of 61% with respect to absorbed power. The beam quality of the waveguide laser was diffraction-limited in the guided axis due to gain selection of the fundamental mode from the multimode double-clad structure'. However, the 5mm wide gain region in the unguided plane led to a highly multimode output in this axis. The prospects for further power scaling and improved beam quality will be discussed.

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More information

Published date: 2001
Additional Information: P1-7
Venue - Dates: QEP-15: 15th Biennial Meeting of the Institute of Physics Quantum Electronics and Photonics Group, United Kingdom, 2001-09-03 - 2001-09-06
Organisations: Optoelectronics Research Centre

Identifiers

Local EPrints ID: 17140
URI: https://eprints.soton.ac.uk/id/eprint/17140
PURE UUID: 998f5b95-5689-4362-a4ed-db1270fb4c9a
ORCID for J.I. Mackenzie: ORCID iD orcid.org/0000-0002-3355-6051
ORCID for D.P. Shepherd: ORCID iD orcid.org/0000-0002-4561-8184

Catalogue record

Date deposited: 16 Sep 2005
Last modified: 06 Jun 2018 13:12

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Contributors

Author: J.I. Mackenzie ORCID iD
Author: S.C. Mitchell
Author: R.J. Beach
Author: H.E. Meissner
Author: D.P. Shepherd ORCID iD

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