利用气源分子束外延技术生长InAs/GaAs量子点激光器材料, 制作了由5层量子点组成的500 μm腔长的激光器。首次使用增益拟合和波长加权的方法计算了激光器的线宽展宽因子。其中, 增益拟合是对Hakki-Paoli方法计算增益的重要补充, 对判断不同电流下的增益是否饱和具有重要作用。对最大模式增益求导数, 当电流为50 mA时, 差分增益最大值为1.33 cm-1/mA, 然后迅速减小到0.34 cm-1/mA, 此时电流为57 mA (≈0.99Ith)。第一次使用加权波长来计算中心波长的移动, 发现Δλ慢慢减小直至接近于0。整个计算方法避免了在直接选取数据点时造成的误差, 线宽展宽因子计算值为0.12~2.75。

A 500-μm-long cavity laser diode with 5 layers of InAs quantum dot was fabricated. The laser materials were grown by gas-source molecular beam epitaxy. For the first time, the linewidth enhancement factor was acquired by gain fitting and weighted wavelength. Gain fitting is an important complement to Hakki-Paoli method, and plays an important role in evaluating whether the gain is saturation. The differential modal gain was evaluated by numerical differentiation of the maximum modal gain. The differential modal gain showed a maximum of 1.33 cm-1/mA at 50 mA, and dropped off to 0.34 cm-1/mA at 57 mA (≈0.99Ith). The weighted average wavelength was treated as central wavelength in order to calculate the wavelength movement. It was found that Δλ decreased slowly until closed to zero. The new method avoids the error due to selecting the data points, and the value of linewidth enhancement factor is from 0.12 to 2.75.