对于顶面出光的浅面浮雕VCSEL结构,有源区的电流密度分布的不均性制约着单模稳定性的提高。为此,提出了一种新型结构: 氧化铟锡透明导电薄膜(ITO)浅面浮雕VCSEL。该结构不仅能够增大高阶模式的阈值增益,还能够提高基模的增益,实现基模对高阶模式的稳定抑制。研究了ITO的厚度对阈值增益的影响及ITO对VCSEL有源区电流密度分布的影响。研究结果表明: 在ITO的厚度为半波长的整数倍时, 基模对高阶模式的限制作用最强; ITO通过改善VCSEL有源区的电流密度分布,达到了增大基模的增益和降低高阶模式增益的目的,同时还降低了串联电阻和外电压。

The mode stability of shallow surface relief vertical cavity surface emitting laser (VCSEL) is constrained by the nonuniform current density distribution in the active region. In order to solve this problem, a new type of structure was put forward, in which indium tin oxide (ITO) transparent conductive layer was employed in shallow surface relief VCSEL. This structure not only can increase the threshold gain of the higher-order modes but also can improve the gain of fundamental model and strengthen the suppressive effect of fundamental mode on higher order mode. The influence of the ITO thickness on the threshold gain and the effect of ITO on the current density distribution in active region are studied. It is found that the suppressive effect of fundamental mode on higher order mode is strongest when the thickness of ITO is integral multiples of the half wavelength. The gain of fundamental mode increases and the gain of higher order decreases with the improving of the current density distribution in the active region of VCSEL, and at the same time, the series resistance and the voltage are also reduced.