High index Er-Yb codoped tellurite spheres with diameter of 9 μm and good sphericity were fabricated using a CO(2) laser. Upconversion modulated whispering gallery modes with a quality factor of 45,000 were observed in the sphere dipped in methanol. Refractometric sensing with detection sensitivity of 7.7 nm/RIU was demonstrated using a 9 μm diameter sphere. Such high index spheres have the potential to be used for nanoparticle sensing and mid-IR frequency conversion.
We present and characterize a simple CO2 laser processing technique for the fabrication of compact all-glass optical fiber cladding light strippers. We investigate the cladding light loss as a function of radiation angle of incidence and demonstrate devices in a 400 μm diameter fiber with cladding losses of greater than 20 dB for a 7 cm device length. The core losses are also measured giving a loss of <0.008±0.006 dB/cm. Finally we demonstrate the successful cladding light stripping of a 300 W laser diode with minimal heating of the fiber coating and packaging adhesives.
We have improved significantly the brightness of cryogenic Ho:YAG, reporting up to 65 W output power with a beam quality of M <1.3 and a slope efficiency of 71%. The laser emission was ~2 nm wide and centered at 2097.5 nm. This result demonstrates the scalability of both the narrow-line thulium fibre pump laser and the cryogenic laser head.
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