D. Allemeier, M. White
University of Vermont,
United States
Keywords: photonic crystal, OLED, spectroscopy, laser
Summary:
A microcavity organic LED (OLED) employs two metallic mirror electrodes to encase the OLED within a resonator cavity. This produces discrete photonic states, analogous to the electronic states of a 1-dimensional quantum square well. Stacking two microcavity OLEDs will split each of these discrete photonic states into two states of slightly higher and lower energy. By stacking more microcavity OLEDs we create a photonic crystal where each of the discrete states splits to form a photonic band with the same number of states as there are microcavities in the stack. Here we demonstrate that the photonic band structure may be tuned by controlling physical properties of the OLED itself and of the photonic crystal stack. The number of states in the photonic band is controlled with the number of stacked cavities, the central wavelength of the band corresponds to the thickness of the OLED, the bandwidth is tuned by varying the mirror thickness, and a mid-band Peierls bandgap is induced by alternating the even and odd mirror thicknesses. Given the wide range of dimensional and compositional variables, we have developed a computational tool capable of accurately simulating the electroluminescence from the devices. The resulting output can be tuned to form narrow linewidth monochromatic light of any color or broadband white light, all from the same green molecular emitter. With the established the experimental and computational protocols, the technology may be easily tuned to produce a series of narrow linewidth emission lines spanning the visible range as a low-fidelity frequency comb for lab-on-chip spectroscopy or optical metrology. It may also be ideally suited for high-intensity electrical pumping, pushing towards the lasing threshold. Being fully compatible with planar, additive manufacturing, the stacked microcavity photonic crystal OLEDs may be easily integrated into any existing display or microchip technology for hybrid electronic/photonic devices.