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Here my labmates and I change the color of LEDs and lasers by freezing them with liquid nitrogen!!

This experiment works by utilizing liquid nitrogen to cool the semiconductor to -196ºC, robbing it of much of its thermal energy. This causes the "bandgap" energy to increase, thereby increasing the emitted photon energy and decreasing the emission wavelength.

Oodles of liquid nitrogen definitely is a perk of working in a NMR lab. :D

Regarding laser safety...This laser was run at just above its threshold current, putting it at 5mW of output power according to my own measurements on an OPHIR laser power meter. At 5mW, this laser is classified as FDA "eye safe" meaning that the blink reflex will prevent any damage from this laser, even from a direct hit. I ALWAYS wear laser goggles when working with lasers over 5mW!!

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