In a potentially important development in green lasers, researchers at Interferometric Optics (Rochester, NY) have created an electrically excited organic-semiconductor device that emits coherent, highly directional light at 545 nm. The researchers have tested the device to confirm its coherent properties; because the device as yet emits only nanowatts of power, an interferometric approach is used to measure linewidth.
The emitter, an organic light-emitting diode, comprises two semiconductor regions doped with Coumarin 545 T dye bracketed by a mirror cathode and an output coupler. To test linewidth, a 150-µm-wide slit is placed immediately in front of the emitter; 130 mm away along the optical axis, dual slits 50 µm wide and 50 µm apart provide the interferometric test. The high measured interferogram visibility of 0.90 approaches that of lasers and is consistent with a broadband (11 nm) dye-laser emission. “To call it a laser in the conventional sense, we need to get inside the submicron cavity and do the usual parametric studies that we do with a laser,” says Frank Duarte, one of the researchers. “This has not been done yet.” Contact Duarte at [email protected].