We report a more than 150 W spectrally-clean continuous wave Raman fiber laser at 1120 nm with an optical efficiency of 85%. A approximately 30 m standard single mode silica fiber is used as Raman gain fiber to avoid second Stokes emission. A spectrally asymmetric resonator (in the sense of mirror reflection bandwidth) with usual fiber Bragg gratings is designed to minimize the laser power lost into the unwanted direction, even when the effective reflectivity of the rear fiber Bragg grating becomes as low as 81.5%.

We report on a 25 W continuous wave narrow linewidth (< 2.3 MHz) 589 nm laser by efficient (> 95%) coherent beam combination of two narrow linewidth (< 1.5 MHz) Raman fiber amplifiers with a Mach-Zehnder interferometer scheme and frequency doubling in an external resonant cavity with an efficiency of 86%. The results demonstrate the narrow linewidth Raman fiber amplifier technology as a promising solution for developing laser for sodium laser guide star adaptive optics.

We demonstrate the cascaded coherent collinear combination of a seed-split triplet of 1178nm high-power narrow-band (sub-1.5MHz) SBS-suppressed CW Raman fibre amplifiers via nested free-space constructive quasi-Mach-Zehnder interferometry, after analysing the combination of the first two amplifiers in detail. Near-unity combination and cascaded-combination efficiencies are obtained at all power levels up to a maximum P(1178) > 60W. Frequency doubling of this cascaded-combined output in an external resonant cavity yields P(589) > 50W with peak conversion efficiency eta(589) ~85%. We observe no significant differences between the SHG of a single, combined pair or triplet of amplifiers. Although the system represents a successful power scalability demonstrator for fibre-based Na-D(2a)-tuned mesospheric laser-guide-star systems, we emphasise its inherent wavelength versatility and consider its spectroscopic and near-diffraction-limited qualities equally well suited to other applications.

BackgroundThere is little indication that foot health services in Australia are meeting modern day recommendations for Rheumatoid Arthritis (RA) patients. The overall objective of this study was to explore the current state of foot health services for patients with RA with an emphasis on identifying barriers to the receipt of appropriate foot care in South-West Sydney, New South Wales, Australia.MethodsA mixed (quantitative and qualitative) approach was adopted. Indications for appropriate access to foot care were determined by comparing the foot health, disease and socio-demographic characteristics of patients with unmet foot care demands, foot care users and patients with no demands for foot care. Perceptions of provision of, and access to, foot care were explored by conducting telephone-based interviews using an interpretative phenomenology approach with thematic analysis.ResultsTwenty-nine participants took part in the cross-sectional quantitative research study design, and 12 participants took part in the interpretative phenomenological approach (qualitative study). Foot care access appeared to be driven predominantly by the presence of rearfoot deformity, which was significantly worse amongst participants in the foot care user group (p = 0.02). Five main themes emerged from the qualitative data: 1) impact of disease-related foot symptoms, 2) footwear difficulties, 3) medical/rheumatology encounters, 4) foot and podiatry care access and experiences, and 5) financial hardship.ConclusionsFoot care provision does not appear to be driven by appropriate foot health characteristics such as foot pain or foot-related disability. There may be significant shortfalls in footwear and foot care access and provision in Greater Western Sydney. Several barriers to adequate foot care access and provision were identified and further efforts are required to improve access to and the quality of foot care for people who have RA. Integration of podiatry services within rheumatology centres could resolve unmet needs of people with RA by permitting rapid access to expert-led multidisciplinary foot care for people with RA.