This paper presents a chip-scale random lasing action utilizing polydimethylsiloxane (PDMS) wrinkles with random periods as disordered medium. Nanoscale wrinkles with long range disorder structures are formed on the oxidized surface of a PDMS slab and confirmed by atomic force microscopy. Light multiply scattered at each PDMS wrinkle-dye interfaces is optically amplified in the presence of pump gain. The shift of laser emission wavelength when pumping at different regions indicates the randomness of the winkle period. In addition, a relatively low threshold of about 27 μJ/mm2 is realized, which is comparable with traditional optofluidic dye laser. This is due to the unique sinusoidal Bragg-grating-like random structure. Contrast to conventional microfluidic dye laser that inevitably requires the accurate design and implementation of microcavity to provide optical feedback, the convenience in both fabrication and operation makes PDMS wrinkle based random laser a promising underlying element in lab-on-a-chip systems and integrated microfluidic networks.
A high-performance binary blazed grating coupler (BBGC) on a silicon-on-insulator (SOI) platform for perfectly vertical coupling has been proposed. The period and the etching depth of the grating and the fill factors of the sub-gratings are simulated optimally with manufacturable feature sizes, and the coupling efficiency (CE) is as high as −1.78 dB at 1550 nm with a broad 3-dB bandwidth of around 100 nm. Then, a BBGC with the CE of −3.69 dB at 1550.5 nm and a 3-dB bandwidth of about 70 nm was experimentally demonstrated. Moreover, a large process tolerance of about 20 nm on the narrower sub-grating width was proved, achieving the insertion loss lower than −4.64 dB at 1550 nm. The realization of the BBGC on a SOI platform is simple, repeatable, and compatible with standard complementary metal-oxide semiconductor (CMOS) technology.
We have investigated the effect of light Si-doping on the optical properties of high quality GaN films with the method of low temperature photoluminescence. It is found that the peak (Ix) at 3.473 eV always appears in the photoluminescence spectra of lightly Si-doped GaN. The relative intensity of peak Ix to heavy-hole free exciton peak increases linearly with the increasing concentration of Si doping, providing a strong support to the assignment that Ix originates from inelastic scattering of free excitons by Si donors. In addition, a rarely reported peak (Px) at 3.365 eV can only be clearly observed in the PL spectrum of unintentionally doped GaN sample. Its intensity is found to reduce dramatically with the decrease of residual carbon concentration based on the secondary ion mass spectrometry analysis. Px is attributed to the excitons bound to carbon-related complex defects.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.