Far-UVC micro-LED arrays for efficient light extraction and fiber coupling

The emission behavior of arrays of far-UVC micro-LEDs emitting at 234 nm has been studied and compared to large area LEDs. The use of the micro-LEDs enhanced the light extraction efficiency by a factor of 2.5 for mesa diameters of 1.5 μm due to a redirection and extraction of TM polarized photons. This redirection also reduces the viewing angle of the emission from the chip from 140° down to 90°. The coupling of the far-UVC light into multimode fibers of 400–910 μm diameter was found to be two times more efficient due to the more directional emission when micro-LED arrays are used, and an overall enhancement of light emission from the fiber by a factor of five was demonstrated for a 1.5 μm micro-LED array in combination with a 910 μm fiber, resulting in a peak power of 0.3 mW from the fiber when the LED was operated at 50 mA and above 1 mW at 200 mA.