It has been 50 years since the first operation of the laser, yet there are still many new applications being made possible by continued innovation in laser technology. A range of exciting optical engineering techniques are currently being developed by scientists and engineers to achieve ever greater precision in sensing, manufacturing, and measurement: from the fabrication of nanometre-scale crystal structures created by laser light patterns to the probing of atomic energy levels to define the time and frequency standards used for communications and navigation. Such visible- and ultraviolet-based (short wavelength) research is very active; however, investigators are currently making do and having to become rather adept at converting current lasers with complex systems for beam shaping, amplification and frequency conversion which generally fall short of the desired wavelength, power and finesse, and confine this technology to the lab. This programme will develop a new class of simplified and tailored short wavelength laser systems in collaboration with these scientists and engineers in order to address a gap in the laser toolbox, dramatically improve capability, and bring these currently specialist techniques out of the lab to the level of widely deployed technology. The core laser technology for the optical engineering systems targeted will be semiconductor disk lasers (SDLs). SDLs are distinct from conventional high performance lasers in that the gain material is engineered on the nanometre scale. Rather than a laser crystal (millimetres long), a flow of dye, or a pressurised tube of gas, light amplification is provided by several quantum wells (QWs): ultra-thin (few nanometres thick) layers of semiconductor, positioned with nanometre-scale accuracy with respect to the light field in the laser. Aside from commercial advantages in terms of compactness, cost and wavelength flexibility, this set-up is fundamentally suited to the very high coherence, low noise laser performance required for ultra-precision optical engineering. Nearly all SDLs operate in the near- or mid-infrared regions of the spectrum; however, many more applications will open up if their full potential for visible and ultraviolet operation is realised. The unique capability in short wavelength SDLs that Dr. Hastie's team has developed over the past 5 years means that she is now in a position to push the technology to target genuine applications for wider benefit. She has identified UK and international research partners for the realisation of high finesse semiconductor laser systems in the visible and UV, together with end users at research institutions in the UK. The Challenging Engineering award will provide the platform necessary to lead this research network and address the identified challenges. Three different optical engineering systems will be targeted initially:* interference lithography - an effective, low-cost method of fabricating nanostructures over a large area and widely deployed in the fabrication of circuits in the semiconductor industry* ultraviolet spectroscopy - for measuring the concentrations of important atmospheric trace gases* optical clocks - for the improvement in time and frequency standards used for communications, satellite navigation and testing of fundamental physics. These areas are complementary in terms of the required laser engineering and performance, will achieve a step-change in capability through the application of short wavelength SDLs, and are sufficiently diverse to provide scope to actively pursue multiple promising research directions and applications, many not yet predicted.