Low-threshold triple-wavelength lasing from a subwavelength triangle microcavity polymer laser fabricated by imaging holography

We propose and demonstrate a low-threshold triple-wavelength polymer laser based on an elaborately designed subwavelength triangle microcavity with high optical confinement. The triangle optical microcavity in three different periodicities is fabricated in a one-step and versatile way by imaging holography. A collimated laser light (for illumination) sheds on a micrometer-scale diffractive optical element (as the object), and diffracted beams are collected by an objective lens (for imaging) and they interfere at the imaging plane, yielding the subwavelength triangle microcavity (as the image) with a demagnification ratio of 100. A novel conjugated polymer blend featuring efficient Forster energy transfer was investigated in detail for its potential as the gain medium. The blended conjugated polymer was overcoated onto the microcavity and lasing at wavelengths of 624.2 nm, 626.3 nm and 630.7 nm was simultaneously observed at a low pump threshold of 1.5 kW/cm(2) . The imaging holography technique provides a flexible approach to yield optical microcavities in constructing multi-wavelength lasers.