Crystalline colloidal arrays: applications in organic lasers

The prospect of an inexpensive organic laser which can dynamically alter its lasing wavelength is desirable for a number of display and communication technologies. In this effort, real-time tuning of the lasing wavelength is accomplished through the use of colloidal crystals to provide the required reflectivity in an external resonator cavity design in which a gain medium is sandwiched between a dielectric stack and colloidal crystal. Optical pumping of the gain medium lead to a lasing peak that corresponded to the stop band of the photonic crystal. By varying the compressive strain placed on the colloidal crystal, the lasing could be tuned across the photoluminescent spectrum of the gain material. Repeated straining of the assembly did not appear to alter its proclivity to lase when photo-excited or introduce hysteresis in the lasing wavelength strain relationship. The fast response of the crystal to compressive strain could lead to pulsed organic lasers operating at kHz modulation frequencies.