Next-generation industrial fiber lasers enable challenging applications that cannot be addressed with legacy fiber lasers. Key features of next-generation fiber lasers include robust back-reflection protection, high power stability, wide power tunability, high-speed modulation and waveform generation, and facile field serviceability. These capabilities are enabled by high-performance components, particularly pump diodes and optical fibers, and by advanced fiber laser designs. We summarize the performance and reliability of nLIGHT diodes, fibers, and next-generation industrial fiber lasers at power levels of 500 W – 8 kW. We show back-reflection studies with up to 1 kW of back-reflected power, power-stability measurements in cw and modulated operation exhibiting sub-1% stability over a 5 – 100% power range, and high-speed modulation (100 kHz) and waveform generation with a bandwidth 20x higher than standard fiber lasers. We show results from representative applications, including cutting and welding of highly reflective metals (Cu and Al) for production of Li-ion battery modules and processing of carbon fiber reinforced polymers.
Phase-contrast radiography (PCR) generates an image from gradients in the phase of the probing X-radiation induced by
the radiographic object, and can therefore make visible features difficult or impossible to see with conventional,
absorption-contrast (ACR) radiography. For any particular object, variations in either the real or imaginary parts of the
index of refraction could be greater. Most practical difficulties of PCR arise from the very small deviation from unity
(~10-5-10-6, depending of material and energy) of the real part of the index of refraction. In principal, straightforward
shadowgraphy would provide a phase-contrast image, but in practice this is usually overwhelmed by the zero-order
(bright field) signal. Eliminating this sets the phase-contrast signal against a dark field (as in Schlieren photography with
visible light). One way to do this with X-rays is with a grating that produces a Talbot interference pattern. Minute
variations in optical path lengths through the radiographic object can significantly shift the Talbot fringes, and these
shifts constitute a dark-field signal separate from the zero-order wave. This technique has recently been investigated up
to ~20keV [1-3]; this work addresses what sets the practical upper limit, and where that limit is. These appear to be
grating fabrication, and ~60keV, respectively.
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