Kuramochi Eiichi, Duprez Hadrien, Kim Junki, Takiguchi Masato, Takeda Koji, Fujii Takuro, Nozaki Kengo, Shinya Akihiko, Sumikura Hisashi, Taniyama Hideaki, Matsuo Shinji, Notomi Masaya
Opt Express. 2018 Oct 1;26(20):26598-26617. doi: 10.1364/OE.26.026598.
Few-cell point-defect photonic crystal (PhC) nanocavities (such as L and H1 type cavities), have several unique characteristics including an ultra-small mode volume (V), a small device footprint advantageous for dense integration, and a large mode spacing advantageous for high spontaneous-emission coupling coefficient (β), which are promising for energy-efficient densely-integratable on-chip laser light sources enhanced by the cavity QED effect. To achieve this goal, a high quality factor (Q) is essential, but conventional few-cell point-defect cavities do not have a sufficiently high Q. Here we adopt a series of modified designs of L cavities with a buried heterostructure (BH) multi-quantum-well (MQW) active region that can achieve a high Q while maintaining their original advantages and fabricate current-injection laser devices. We have successfully observed continuous-wave (CW) lasing in InP-based L1, L2, L3 and L5 PhC nanocavities at 23°C with a DC current injection lower than 10 μA and a bias voltage lower than 0.9 V. The active volume is ultra-small while maintaining a sufficiently high confinement factor, which is as low as ~10 cm for a single-cell (L1) nanocavity. This is the first room-temperature current-injection CW lasing from any types of few-cell point-defect PhC nanocavities (L or H1 types). Our report marks an important step towards realizing a nanolaser diode with a high cavity-QED effect, which is promising for use with on-chip densely integrated laser sources in photonic networks-on-chip combined with CMOS processors.
少单元点缺陷光子晶体（PhC）纳米腔（如L型和H1型腔）具有几个独特的特性，包括超小模式体积（V）、有利于密集集成的小器件尺寸，以及有利于高自发辐射耦合系数（β）的大模式间距，这些特性对于通过腔量子电动力学（QED）效应增强的节能密集可集成片上激光光源很有前景。为了实现这一目标，高品质因数（Q）至关重要，但传统的少单元点缺陷腔没有足够高的Q值。在这里，我们采用了一系列带有掩埋异质结构（BH）多量子阱（MQW）有源区的L型腔的改进设计，这种设计可以在保持其原有优势的同时实现高Q值，并制造出电流注入激光器件。我们已经成功地在基于InP的L1、L2、L3和L5 PhC纳米腔中，于23°C下通过低于10 μA的直流电流注入和低于0.9 V的偏置电压观察到了连续波（CW）激光发射。有源体积超小，同时保持足够高的限制因子，对于单单元（L1）纳米腔，该限制因子低至约10 cm。这是首次从任何类型的少单元点缺陷PhC纳米腔（L型或H1型）实现室温电流注入CW激光发射。我们的报告标志着朝着实现具有高腔QED效应的纳米激光二极管迈出了重要一步，这对于与结合CMOS处理器的片上光子网络中的片上密集集成激光源一起使用很有前景。
