High-quality-factor EH modes in microcylinder resonators predicted by 3D FDTD simulation

The mode characteristis of a microcylinders with center layer thickness 0.2 mu m and radius 1 mu m are investigated by the three-dimensional (31)) finite-difference time-domain (FDTD) technique and the Pade approximation. The mode quality factor (Q-factor) of the EH71 mode obtained by 3D FDTD increase with the increase of the refractive index of the cladding layer n(2) as n(2) smaller than 3.17, and can be as large as 2.4 x 10(4) as the vertical refractive index distribution is 3.17/3.4/3.17, which is much larger than that of the HE71 mode with the same vertical refractive index distribution.

AlGaInAs-InPMicrocylinder Lasers Connected With an Output Waveguide

AlGaInAs-InPmicrocylinder lasers connected with an output waveguide are fabricated by planar technology. Room-temperature continuous-wave operation with a threshold current of 8 mA is realized for a microcylinder laser with the radius of 10 mu m and the output waveguide width of 2 mu m. The mode Q-factor of 1.2 x 10(4) is measured from the laser spectrum at the threshold. Coupled mode characteristics are analyzed by 2-D finite-difference time-domain simulation and the analytical solution of whispering-gallery modes. The calculated mode Q-factors of coupled modes are in the same order as the measured value.

平面工艺制作的定向输出微腔半导体激光器

光学微腔中偶极子自发辐射受到空间和频谱调制,能实现自发辐射增强或抑制效应,而且其有源区体积可以非常小,有利于极低阈值工作和极高的调制速率.在过去的二十多年来,垂直腔面发射激光器、回音壁模式(whispering-gallery mode)微腔激光器以及光子晶体微腔激光器三类光学微腔激光器的研究取得了很大的进展.回音壁模式微腔中,模式光线由于其在微腔界面的入射角大于全反射临界角而受到限制,是一种结构非常简单的光学微腔.微盘激光器作为典型的回音壁模式微腔激光器,可利用普通的边发射激光器外延片材料,采用半导体平面工艺制作,引起了人们很大的重视.但圆对称结构的微盘激光器易于实现回音壁模式的全反射限制,却难以得到定向的激光输出,限制了它的应用.人们往往采用局部破坏圆盘的对称性、整体变形以及消逝波耦合的输出波导实现微盘激光器的定向激光输出.在圆对称的微盘结构中,模式光线在微腔与空气界面上的入射角是恒定的,而在整体变形的圆盘中,如椭圆形微腔中,模式光线在界面的入射角则不断变化,并在某些位置上小于全反射临界角而折射出光学微腔,从而实现定向输出.这种变形微盘中模式光线往往具有混沌现象,因而吸引了人们的注意.

InGaAsP/InP正方形微腔激光器

采用平面工艺制作的定向输出微腔半导体激光器是集成光学回路的理想光源.近十几年来,以微盘为代表的回音壁模式(whispering-gallery mode)微腔激光器引起人们很大的重视.但圆对称的微盘激光器缺乏定向的激光输出,人们往往利用输出波导与微盘实现消逝波耦合或通过改变微盘的对称性来实现定向输出.最近几年,多边形微腔如正三角形、正方形、长方形、六边形等多边形光学微腔也引起人们的重视.多边形光学微腔中也能有高Q值的类回音壁模式.而且由于不具有圆对称性,其模式特性有利于简单地实现定向光输出.

Lasing of CdSSe quantum dots in glass spherical microcavity

Glass spherical microcavities containing CdSSe semiconductor quantum dots (QDs) of a few microns in diameter are fabricated using a physical method. When a single glass microspherical cavity is excited by a laser beam at room temperature, very strong and sharp whispering gallery modes are shown on the background of PL spectra of CdSSe QDs, which confirms that coupling between the optical emission of embedded QDs and spherical cavity modes is realized. For a glass microsphere only 4.6 mum in diameter, it was found that the energy separation is nearly up to 26 nm both for TE and TM modes. With the increasing excitation intensity, the excitation intensity dependence of the emission intensity is not linear in the double-logarithmic scale. Above the threshold value, the linewidths of resonance modes become narrower. The lasing behavior is achieved at relatively low excitation intensity at room temperature. High optical stability and low threshold value make this optical system promising in visible microlaser applications. (C) 2002 Elsevier Science B.V. All rights reserved.