Planar Waveguide and Slab Lasers

The Planar Waveguide and Slab Lasers group is led by Dr Jacob Mackenzie.

To extend the applicability of the active planar waveguide and slab geometries for laser devices by enhancing the range of accessible wavelengths; demonstrating power-scaling solutions suitable for the industrial and commercial arena in the CW and pulsed regimes; while at the other end of the power spectrum, providing a route toward integration and miniaturisation.

• Original resonator and laser configurations that demonstrate the key benefits offered by waveguide, slab, and hybrid laser architectures
• Efficient, compact, and powerful solid-state laser systems, difficult to realise using other laser-media geometries.
• Visible laser devices
• Novel waveguide structures for robust spatial mode selection
• Devices, compatible with high average-power diode-pumping
• Pulsed planar waveguide lasers with high-peak powers
• Diode pumped slab lasers for pulse energy scaling
• Waveguide amplifiers

Axisymmetric Laser Sources with Planar Gain Media

This project is funded by the EPSRC First Grant Scheme to explore an original approach for generating circular laser beams from thick and thin slab-like gain media.

We are exploring novel resonator and laser configurations (e.g. high-average-power CW and Q-switched lasers) to demonstrate the key benefits offered by the slab geometry. Mainly because these methods offer the potential for high average power and high brightness with the added flexibility of being able to choose the mode of operation, such as pulsed or continuous wave, suitable for a range of applications in the industrial and scientific arenas. Our ambition is to obtain circular laser beams with good beam quality, from planar active media that can both rival and complement solid-state sources based on fibre and thin-disc technologies.

MULTI-WATT IN-PLANE DIODE-PUMPED WAVEGUIDE LASERS

High-power, diode-pumped, solid state lasers are finding an increasing number of applications in various industrial and scientific sectors. However, the non-diffraction-limited and asymmetric nature of the output of diode-bars normally requires the use of rather complicated and expensive beam shaping to allow efficient pumping of either bulk or fibre media. In collaboration with Onyx Optics, we successfully showed that active planar waveguides as the laser host were ideally suited to the out put of diode bars, even allowing direct in plane proximity coupling. Along with the advantages normally associated with waveguides - high gain per unit pump power and good spatial overlap - the planar geometry is also ideally suited for handling the high thermal load associated with high power devices. These systems lend themselves to integration of novel resonators, Q-switching functions, polarisation control etc., thus leading to highly compact and versatile, high-power, lasers. We demonstrated multi-watt, near diffraction-limited, diode-pumped waveguide lasers at 1µm (Nd,Yb), 2µm Tm, and 3µm (Er), with a simple and very compact design.

HIGH-POWER, ND-INDIFFUSED-YVO4, TAPERED WAVEGUIDE LASERS

Compact laser sources of high average power and good beam quality are needed for a variety of industrial, medical and research applications. This has inspired work on diode-bar-pumped waveguide lasers, as planar waveguides are compatible with the asymmetric beam-shape of diode-bars, leading to highly-compact coupling schemes. However, the output of the waveguide laser is far from diffraction-limited in the non-guided plane because of the broad gain region and the use of short monolithic resonators. Here we had proposed the use of adiabatic waveguide tapers that couple the planar diode-bar-pumped region to a single mode channel section, leading to near-diffraction-limited output. A low-loss taper design can expand up to 200um in a few cm. This is compatible with diode-bar side-pumping if a material with a strong absorption for the diode emission is used. For this reason we also began to develop Nd-indiffused waveguide fabrication in Yttrium Vanadate. This required the study of the diffusion characteristics and waveguide fabrication in this important material.

Novel Stable Resonator Concept for Efficient Axisymmetric Output from Lasers with a Planar Gain Medium
J. I. Mackenzie and W.A. Clarkson, Conference on Lasers and Electro Optics, Long Beach, 2006, CFB4

A power scaling strategy for longitudinally diode-pumped Tm:YLF lasers
S. So, J. I. Mackenzie, D. P. Shepherd, W. A. Clarkson, J. G. Betterton, and E. K. Gorton, Applied Physics B, vol. 84, pp. 389-393, 2006.

Multi-watt, high efficiency, diffraction-limited Nd:YAG planar waveguide laser
J. I. Mackenzie, C. Li, and D. P. Shepherd, IEEE Journal of Quantum Electronics, vol. 39, pp. 493-500, 2003.

End-pumped, passively Q-switched Yb: YAG double-clad waveguide laser
J. I. Mackenzie and D. P. Shepherd, Optics Letters, vol. 27, pp. 2161-2163, 2002.

Schematic for the end-pumping configuration

Schematic (left) and photo of optical coupling scheme for end-pumping configuration (right)

Dr Jacob Mackenzie is a Postdoctoral Research Fellow of the Royal Academy of Engineering 2004-2009 www.raeng.org.uk

Within the ORC the Planar Waveguide and Slab Lasers group collaborates closely with the

• Advanced Solid State Sources Group
• Pulsed Laser Deposition (PLD) Group

Externally, the group collaborates with Onyx Optics www.onyxoptics.com/. This company developed a technique for robust bonding of dissimilar materials suitable to waveguide geometries.