Researchers from the Sensor Device Business Unit, Device Department, Shimadzu (Kanagawa, Japan) have created a blue-emitting direct diode laser that focuses light from 30 individual 450-nm-emitting laser diodes into an optical fiber with a 100-μm-diameter core; the direct-diode laser produces 50 W of optical power at a numerical aperture (NA) of 0.2. The laser's wavelength is much better suited than near-IR laser light for some materials-processing applications—for example, machining copper (Cu) and gold (Au).
One of the notable characteristics of this laser is its electrical-power to light-conversion (wall-plug) efficiency of 20%.
The laser uses a spatially multiplexed beam-combining arrangement, in which collimated beams from all the laser diodes are aligned in parallel and sent through a lens that focuses the resulting beam onto the input end of the fiber. The researchers decided to forgo using spectral multiplexing (combining laser diodes of different wavelengths using dichroic optics), as that approach requires preparing light sources with multiple wavelengths and and produces an output with a broader spectrum.
The researchers started with a basic unit containing five laser diodes; two of these units were first combined to make a 10 W direct diode laser whose output is high enough on its own to anneal amorphous silicon or weld plastics. The laser showed a wavelength variability of less than 0.04 nm/°C over the 15 °C to 30 °C temperature range.
They then used the same spatial multiplexing approach to create the 50 W laser (shown in figure). Future research includes higher-power lasers of this type.
For more info, see: http://www.shimadzu.com/products/opt/laser/5iqj1d000002095b.html
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