Optically pumped lasing with a Q-factor exceeding 6000 from wet-etched GaN micro-pyramids

Whispering-Gallery Mode Lasing in a Floating GaN Microdisk with a Vertical Slit

Controlling the lasing mode, emission direction, threshold, and quality factor of whispering-gallery mode lasing is important for practical applications such as optical interconnections, on-chip communications, trace detection, high-density storage, etc. In order to simultaneously control the mode and emission direction and to achieve a high-quality factor in a low-threshold whisper-gallery mode laser, such as a GaN floating microdisk, a novel fabrication design of a microdisk with a vertical slit is proposed. To demonstrate proof of concept, we experimentally measure whispering-gallery mode lasing spectra of microdisks with and without a slit. Our findings suggest that the disks can indeed operate in whispering-gallery mode, and the slit is able to change the optical path in the microcavity without breaking lasing resonance. The slit in the microdisk can also influence the lasing mode, quality factor, and directional emission. Therefore, our study provides a feasible way to control whispering-gallery mode lasing properties.

Ultraviolet nanolaser of inverted hexagonal ZnO pyramid resonating in helical whispering-gallery-like mode

ZnO nanocavities have advantage to working as optoelectrical nanodevices integrated on chip at high temperature owing to high exciton binding energy. In this work, a single inverted hexagonal ZnO pyramid (HZOP) nanolaser is fabricated successfully by reducing the defect with chemical vapor deposition (CVD). The optical leakage of HZOP is conquered by the inverted configuration to increase the refractive index contrast between ZnO pyramid and surrounding media. Helical whispering-gallery-like mode is proposed to dominate the lasing of HZOP nanolaser. All of the lasing peaks are found to exist at wavelength longer to the fluorescence emission of ZnO, which is ascribed to the large loss represented by the large imaginary part of ZnO refractive index at shorter wavelength. The threshold and linewidth are measured to be 5.27 mJ/cm² and 0.27 nm, respectively. HZOP nanolaser is a new ultraviolet coherent light source to be integrated on chip at room temperature or higher temperature.

Omnidirectional whispering-gallery-mode lasing in GaN microdisk obtained by selective area growth on sapphire substrate

The optical properties of hexagonal GaN microdisk arrays grown on sapphire substrates by selective area growth (SAG) technique were investigated both experimentally and theoretically. Whispering-gallery-mode (WGM) lasing is observed from various directions of the GaN pyramids collected at room temperature, with the dominant lasing mode being Transverse-Electric (TE) polarized. A relaxation of compressive strain in the lateral overgrown region of the GaN microdisk is illustrated by photoluminescence (PL) mapping and Raman spectroscopy. A strong correlation between the crystalline quality and lasing behavior of the GaN microdisks was also demonstrated.

Room-temperature high-performance CsPbBr3 perovskite tetrahedral microlasers

With the goals of faster coherent light sources with lower power consumption, laser miniaturization has been intensively pursued in the past four decades. Novel microscale cavities with efficient feedback and distinct emission profiles are essential for excellent performance of laser devices and for exploring their new functionalities. Here, for the first time, well-defined high-quality tetrahedron-shaped CsPbBr3 perovskite microcavities with smooth surfaces were synthesized via the vapor growth method. A room-temperature high-performance tetrahedral microlaser was realized based on CsPbBr3 perovskite single crystals. The three-dimensional total internal reflection mode inside the tetrahedral cavity led to a high-performance microlaser with a linewidth of only ∼0.3 nm at 538 nm emission wavelength and a unique profile with three emission beams into free space with triangular symmetry. In addition, the perovskite tetrahedral microlasers could be pumped by two-photon absorption with threshold only about 2.5 times higher than that of a one-photon laser. The high-performance tetrahedral microlaser with a distinct emission profile enriches the microscale laser family and may find exceptional applications in optical manipulation, communication and on-chip beam steering.