Spatially variant color light source using amplified spontaneous emission from organic thin films

Color tunable light source has great potential for display, lighting, bio-imaging, and so on. Current broadband light sources including halogen lamp, super continuum laser, inorganic and organic light emission diode have been widely used for these purposes. However, each of them has their own limitations in beam divergence, cost and device size. In this work, we demonstrate a spatially variant light source with tunable color emission property by using two cascaded organic thin films, which emit blue and green light respectively under optical pumping. By spatially selecting the overlapping of the directional amplified spontaneous emission from the cascaded films, we show that the color of light emission can be continuously tuned from blue, white to green. The method we propose here also indicates a potential way to design stripe light source for high resolution bio-imaging.