Stable dual-mode semiconductor lasers can be applied for the photonic generation of microwave and terahertz waves. In this paper, the mode characteristics of a variable curvature microresonator are investigated by a twodimensional finite element method for realizing stable dual-mode lasing. The microresonator features a smooth boundary and the same symmetry as a square resonator. A small variable-curvature microresonator with a radius of 4 μm can support the fundamental four-bounce mode and the circular-like mode simultaneously, with quality factors up to the order of 10~4 and 10~5, respectively. The dual modes in the phase space of the Poincarésurface of sections distribute far from each other and can maintain enough stability for dual-mode lasing.Furthermore, the refractive index and waveguide can modulate the dual-mode wavelength difference and quality factors efficiently thanks to the spatially separated fields of these two modes.
MIN TANGYONG-ZHEN HUANGYUE-DE YANGHAI-ZHONG WENGZHI-XIONG XIAO
Square and circular resonator microlasers connected with two output waveguides are investigated for correlation of output powers from the two output ports.The square resonator microlasers with two output waveguides connected at the midpoint of one side and one vertex are fabricated and tested by measuring the output power versus injection current and the laser spectra of the two ports.The laser spectra indicated that the output power correlation between the two output ports is very weak because of different lasing modes in different ports of the square microlaser.Circular resonator microlaser with two output waveguides can realize single mode operation and has good output correlation from the two ports.So the output power from one port of the circular microlasers can be monitored by that of another port.
Degradation phenomenon and poor stability of tris（8-hydroxyquinoline） aluminum（Ⅲ）（Alq3）-based organic light-emitting diodes（OLEDs） have attracted much attention. In this paper, we discussed the origin of instability of the facial Alq3-based blue luminescent OLEDs with the help of first-principles calculation. The results show that environmental humidity seriously affects the luminescence stability of Alq3-based OLEDs. H20 molecules in envi- ronment can be firmly bound to the oxygen atoms of the facial Alq3, which then act as starting points for further de- gradation of Alq3. Moreover, the interactions between facial Alq3 and different cathode metal layers were investigated to explain the experiment phenomenon. A design guideline for diminishing the strong attraction from oxygen atoms can be proposed to protect Alq3 and improve the stability of materials applied in OLEDs.
DU JiarenWANG MoranCHEN NiankeXIE ShengyiYU HongmeiWU Qi
Relative intensity noise(RIN) and high-speed modulation characteristics are investigated for an Al Ga In As/In P hybrid square-rectangular laser(HSRL) with square side length, rectangular length, and width of 15,300, and 2 μm, respectively. Single-mode operation with side-mode suppression larger than 40 dB has been realized for the HSRL over wide variation of the injection currents. In addition, the HSRL exhibits a 3 dB modulation bandwidth of 15.5 GHz, and an RIN nearly approaches standard quantum shot-noise limit 2 hv∕P=-164 dB∕Hz at high bias currents due to the strong mode selection of the square microcavity. With the increase of the DC bias current of the Fabry–Perot section, significantly enhanced modulation bandwidth and decreased RIN are observed.Furthermore, intrinsic parameters such as resonance frequency, damping factor, and modified Schawlow–Townes linewidth are extracted from the noise spectra.
