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Very recently, perovskite based microdisk lasers have attracted considerable research attention. However, most of the researches are focused on the lasing spectra in bottom-up synthesized microdisks with regular shapes. The directionality, which is also essential for practical applications, has not been explored. Here we demonstrate unidirectional lasing emissions from perovskite microdisks for the first time. We synthesized the rectangle-shaped microdisks connected with straight waveguides and studied the lasing characteristics, where unidirectional emissions along the waveguides have been observed. Numerical calculations reveal that the unidirectional emissions are formed by the breaking of total internal reflections at the joints between waveguides and microdisks. Since waveguides are compatible with other photonic elements, we believe that our finding will be essential for the applications of perovskite microdisks in integrated photonic circuits and networks.

Light confinement and amplification in micro- and nanofibers have been intensively studied, and a number of applications have been developed. However, typical micro- and nanofibers are usually free-standing or positioned on a substrate with lower refractive index to ensure the light confinement and guiding mode. Here we numerically and experimentally demonstrate the possibility of confining light within a microfiber on a high refractive index substrate. In contrast to the strong leakage to the substrate, we found that the radiation loss was dependent on the radius of the microfiber and the refractive index contrast. Consequently, quasi-guiding modes could be formed and the light could propagate and be amplified in such systems. By fabricating a tapered silica fiber and dye-doped polymer fiber and placing them on sapphire substrates, the light propagation, amplification, and consequent laser behaviors have been experimentally studied to verify the quasi-guiding modes in a microfiber on a higher index subst...