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We report on organic semiconductor lasers based on spiro-terphenyl as active gain medium in a second-order distributed feedback (DFB) structure. In contrast to neat p-terphenyl, the spiro-linked compound forms vitreous amorphous films—an essential prerequisite for low loss laser structures. Spiro-terphenyl shows amplified spontaneous emission in the ultraviolet part of the spectrum at 381 nm. Thin-film lasers with DFB grating periods between 200 and 230 nm exhibit emission wavelengths between 361.9 and 393.8 nm. The minimum threshold energy density under optical pumping is as low as 8.9μJ∕cm2 (383 nm). Therefore, the novel spiro-linked compound paves the way for low-threshold, widely tunable organic semiconductor lasers advancing into the ultraviolet spectral region.

Thin films of spirobifluorene-type materials, namely, spiro-octo1 and spiro-octo2, were investigated by means of spectroscopic ellipsometry in a broad spectral range from near-infrared to vacuum ultraviolet. The optical response of the amorphous organic films was described by an isotropic layer model based on Tauc–Lorentz functions. The dielectric functions of both types of organic films were determined. The strongest light absorption occurs around 6eV for both types of organic films. The more effective π-conjugation of spiro-octo2 redshifts by 160meV the absorption edge compared to Spiro-Octo1.