Microdisk lasers with active region made of type-II GaSb/GaAs quantum dots on the GaAs substrate have been demonstrated. A microdisk cavity with diameter of 3.9 m was fabricated from a 225-nm-thick GaAs layer filled with GaSb quantum dots. Lasing at wavelengths near 1000 nm at 150 K was achieved for this microdisk. A high threshold characteristic temperature of 77 K was also observed. It is found that the lasing wavelength matches closely with the first-order whispering-gallery mode of the cavity as obtained from the finite-element method simulation.
A new molybdenum (vi) arsenate, (C,H,N H),( Mo,O,) (HAsO,),~H,O, has been synthesised hydrothermally at 230 "C and characterized by single-crystal X-ray _diffraction and thermogravimetric analysis. The compound crystallizes in the triclinic space group PI with a = 7.708(1), b = 12.262(3). c = 12.281 (4) A, a = 11 5.98(2), p = 103.36(2), y = 98.71 (2)". 2 = 2 and R = 0.0293. The structure is composed of pyridinium cations, water molecules and [ (Mo,O,,) ( HAs0,),I4-cluster anions. The anions, which lack Mo-Mo bonds, are linked by strong hydrogen bonds to form layers parallel to the ac plane with pyridinium cations between the layers. Water molecules are within the layers and are linked to both the cluster anions and pyridinium cations through hydrogen bonding.
In this paper, a chip-scale compact optical curvature sensor was demonstrated. It consists of a low threshold InGaAsP microdisk laser on a flexible polydimethylsiloxane polymer substrate. The curvature dependence of lasing wavelength was characterized by bending the cavity at different bending radii. The measurements showed that the lasing wavelength decreases monotonously with an increasing bending curvature. A good agreement between experiment and three-dimensional finite-difference time-domain simulation was also obtained. The sensitivity of the compact device to the bending curvature is -23.7 nm/mm form the experiment.
This study demonstrates a room-temperature ultraviolet GaN/Al nanorod (NR) metal laser with an optimized sidewall. A wet-chemical etching process with potassium hydroxide was used to control the GaN NR sidewall angle and polish the NR surface. The lasing action was observed near a wavelength of 365 nm with a low threshold power density of 5.2 mJ/cm 2. The high-quality factor (Q) surface plasmon lasing modes were characterized with experiments and three-dimensional finite-element method simulations. We also studied the optical modes in GaN metal-coated NR with and without an Al layer and verified the metal layer is necessary for high-Q resonant modes.
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