Ultra-low threshold and spontaneous emission control in semiconductor microdisk lasers

我们在微盘激光器方面取得了以下成果：1.超小型腔：在直径2 μ m、厚度0.2 μ m的GaInAsP微盘中获得了注入激光。空腔体积为0.4 μ m^3。虽然这个值大于在单个缺陷光子晶体激光器中实现的值，但它仍然是注入激光器中最小的。这样小的空腔为自发辐射控制提供了多种证据.在连续工作条件下，获得了超低阈值：I_0 = 40 μ A，为GaInAsP激光器的最低阈值。<th>有效J_2为320 A/cm_2（80 A/cm_2/QW）。<th>降低阈值的关键问题是减少由微盘中的粗糙度引起的散射损耗，以及载流子扩散和柱边缘处的散射损耗之间的平衡。通过对回音壁模式、自由载流子吸收、量子阱中的应变弛豫等的工程化处理，使阈值电流小于10 μ A，内效率大于50%成为可能.脆弱性：这将 ...更多信息 我在未来的应用中会有问题。为了同时满足机械强度和光学约束的要求，提出了一种选择性氧化AlInAs包层掩埋的微盘。氧化层的厚度和光吸收是研究的关键问题.强光学约束：由于在微盘边界处的全内反射而获得低阈值，这不适合于光提取。利用时域有限差分法（FDTD）对微盘元件的倏逝波耦合进行了模拟研究。通过&lt;0.3 μ m的微盘元件之间的间距，预期超过60%的提取效率.在微盘周围扩散的渐逝场：该特征可用于近场探针传感器。激光的特性是由一个物体的表面轮廓靠近微盘调制。理论上和实验上都预期空间分辨率为λ/10。通过使用这种有源探针，证明了对金属和电介质物体的扫描显微镜。少

We obtained the following achievements on microdisk lasers :1. Ultra-small cavity : The injection lasing was obtained in 2-μm-diameter and 0.2-μm-thickness GaInAsP microdisk. The cavity volume is 0.4 μm^3. Although this value is larger than that achieved in a single defect photonic crystal laser, it is still the smallest for injection lasers. Such a small cavity provides various evidences of the spontaneous emission control.2. Ultra-low threshold : I_<th>=40μA was achieved under cw condition, the lowest record for GaInAsP lasers. The effective J_<th> is 320 A/cm_2 (80 A/cm_2 per QW). Key issues for lower threshold are the reduction in scattering loss caused by the roughness in the microdisk, and the balance between the carrier diffusion and the scattering loss at post edges. A threshold less than 10 μA and internal efficiency higher than 50 % will be possible by the engineering of whispering gallery modes, free carrier absorption, strain relaxation in QWs, etc.3. Fragileness : This wil … More l be a problem in future applications. To satisfy both the mechanical strength and optical confinement, a microdisk buried by the selectively oxidized AlInAs claddings was proposed. The depth and the optical absorption in the oxidized claddings are key issues to be investigated.4. Strong optical confinement : The low threshold is obtained by the total internal reflection at microdisk boundaries, which is unsuitable for light extraction. The evanescent coupling of microdisk elements was investigated by the FDTD simulation. Over 60 % extraction efficiency is expected by the <0.3 μm space between the microdisk elements.5. Evanescent field spreading around the microdisk : This feature can be used in a near field probe sensor. The lasing characteristic is modulated by the surface profile of an object put close to the microdisk. A spatial resolution of 〜λ/10 were expected theoretically and experimentally. The scanning microscopy against metal and dielectric objects was demonstrated by the use of this active probe. Less