Diode-pumped Ti:sapphire lasers: a manufacturable platform for precision photonics

Lead Research Organisation: University of Strathclyde
Department Name: Inst of Photonics

Abstract

Ti:sapphire lasers set the standard for precision in instrumentation. However, commercial systems are bulky and complex to make, due in large part to the requirement for a painstakingly manufactured pump laser. The potential exists to replace these complex pump lasers with mass-produced, compact, and inexpensive diode lasers if we can unpick the physics of the light-matter interactions that govern the efficiency. This programme will lead to a step-change in our understanding, allowing us to redesign Ti:sapphire lasers from the ground up, tailoring them for diode-pumping and enabling high-end applications beyond the laser lab, initially in portable quantum technologies and analytical instrumentation.

This project will -

- Fully describe the underlying physics of pump-induced losses in Ti:sapphire crystals for the first time.

- Initiate the development of a manufacturable, platform laser technology with the performance of Ti:sapphire but the practicality of diode-pumping.

- Identify the combinations of diode-laser and Ti:sapphire crystal specification required to maximise both the wall-plug efficiency and manufacturability of Ti:sapphire lasers.

- Develop exemplar narrow-linewidth and dual-comb demonstrators for future development towards applications in optical clocks and combustion analysis.

The investigator team for this project brings together the grouping that demonstrated the first diode-pumped Ti:sapphire laser with experts in narrow-linewidth lasers for quantum technologies and laser spectroscopy for combustion analysis. The project partners include one of the world's leading manufactures of high-specification lasers (Coherent Scotland), the world's leading manufacturer of Ti:sapphire crystals (GTAT Corporation), a high-power visible diode-laser systems manufacturer (Arctos Lasertechnik), and the UK National Quantum Technologies Hub for Sensors and Metrology. An advisory panel of representative for these organisations, together with experts on technology transfer in the manufacturing of lasers and industrial gas-sensing, will provide the investigator team with strong industrial guidance and a route to accelerate economic and societal impact.

Planned Impact

This programme is fundamentally about delivering the performance benefits of Ti:sapphire in a package and at a price-point that drives its wider use. In doing this, the programme will have impact on the following groups:

Laser Manufacturers

Around half of the complexity and cost of current Ti:sapphire lasers resides in the high-specification pump laser. Replacing this high cost sub-system (tens of thousands of pounds) with mass-produced diode lasers will ease manufacture, reduces costs, and increase sales by opening up markets beyond the optics lab. More specifically, this programme will deliver for laser manufacturers in three ways:

- The comprehensive study the relationship between crystal specification, pump wavelength, and overall system efficiency will provide a roadmap for product design.
- The exploitation of diode pumping to allow for the use of multiple pump lasers will enable power scaling and increase reliability (through pump redundancy), while direct modulation of the pump current will enable intensity stabilisation.
- The demonstration of narrow-linewidth and dual-comb lasers will seed new market in portable quantum technologies and analytical instrumentation.

(See also Letters of Support from Coherent Scotland Ltd., GTAT Corp., and Arctos Lasertechnik GmbH.)

End-Users and System Developers

The two exemplar applications targeted illustrate the potential of taking Ti:sapphire lasers out of the optics lab, although in the long term the impact is likely to be much broader given the breadth of applicability of conventional Ti:sapphire lasers.

- The 813nm narrow linewidth laser targeted here will assist in the development of high-end, yet transportable, optical clocks based on neutral Strontium. This wider field is expected to have considerable impact on applications including GPS-denied navigation and synchronisation of communications networks, power grids, and financial markets. (See also the Letter of Support from the Quantum Technology Hub for Sensors and Metrology.)
- The dual-comb laser targeted here has the potential to be a robust and portable tool for analytical instrumentation. This project will target combustion and exhaust diagnostics as an exemplar - which will have impact in aero-engine development and predictive maintenance. However, wider application of robust dual comb spectroscopy tools, for example for in-line analysis of fuel for gas-fired power stations and of pharmaceuticals during manufacture, are likely to develop as the technology matures.

Wider Society

Just as many of the profound implications of the invention of the conventional Ti:sapphire laser were unforeseen, so are many of the implications of more manufacturable Ti:sapphire lasers likely to be unforeseeable. However, two exemplar applications give some feeling for the breadth and depth of the societal impact can be garnered. Should the development of the narrow linewidth 813nm laser proposed here contribute, as it is expected to do, to the wider challenge of realizing high performance yet portable optical clocks, then the societal impact is potentially considerable. In particular, disruption to GPS systems for only 5 days would result in an estimated £5.2bn loss of UK GDP. Robust optical clocks are necessary to mitigate against this. Should the development of dual comb lasers in turn contribute, as it is expected to do, to the development of portable analytical tools for combustion and exhaust diagnostics, this would enable emissions monitoring of aero engines during every routine service (enabling preventative maintenance) - which is not practical currently. This sort of analytical capability would help to reduce the environmental impact of gas turbines and internal combustion engines. This in turn would permit enforcement of stricter emissions standards, while supporting UK manufactures (e.g. Rolls Royce, Siemens UK, Caterpillar UK, BMW UK) in reducing the carbon footprint of their products.

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