Figure 2
From: Organic Single-Crystal Light-Emitting Transistor Coupling with Optical Feedback Resonators
Organic single-crystal waveguide and resonator.
(a) Molecular structure and optical micrograph of α,ω-bis(biphenyl)terthiophene (BP3T) under white (left) and ultraviolet (right) light exposure. (b) A single BP3T crystal imaged by atomic force microscopy. The image shows clear terraces in the BP3T molecular layers. The step height agrees with the c-axis height of the crystal unit cell. (c) Comparison of the integrated intensity of the (0–1) (λ = 576 nm) peak between a BP3T single crystal with rounded edges (red circle) and a BP3T single crystal with parallel edges (blue square) as a function of the pump laser fluence. The insets show the photoluminescence spectrum of the BP3T crystal with parallel edges as a function of the pump laser fluence (upper right) and optical micrographs of the corresponding crystals (a parallel-edge crystal (upper middle) and a round-edge crystal (bottom right)). The yellow lines indicate the excitation beam. (d) Comparison of the laser-fluence-dependent (0–1) spectral linewidth (full width at half maximum, FWHM) of the respective BP3T crystals. (e) Laser oscillation spectra of the BP3T crystal due to the natural Fabry-Perot resonator of parallel crystal edges. The inset shows an optical micrograph of a corresponding BP3T crystal under ultraviolet light.
