Li Nanguo, Ma Yuting, Liu Can, Li Guojiong, Zhang Yuanhao, Lu Qiaoyin, Guo Weihua
Opt Express. 2025 Jul 14;33(14):29635-29647. doi: 10.1364/OE.560886.
Single-mode surface-emitting lasers are crucial for emerging mega- and hyper scale data centers, providing a cost-effective solution for high-bandwidth, long-reach data communication systems. However, grating-coupled surface-emitting lasers, which are commonly used to achieve single-mode surface emission, often suffer from low slope efficiency and high thresholds. In this study, we report a high slope efficiency single-mode surface-emitting distributed feedback laser featuring an optimized λ/4 phase shift position within the second-order grating region and an unpumped distributed Bragg reflector. The specific positioning of the λ/4 phase shift relative to the second-order grating significantly influences the interaction between the second-order grating and the longitudinal optical field, thereby affecting its diffraction performance. When the λ/4 phase shift is placed in the first-order grating etching region adjacent to the second-order gratings, we achieved the highest vertical upward diffraction from the second-order gratings. This optimization resulted in a slope efficiency of 0.3 mW/mA for the fabricated device. Incorporating a bottom DBR mirror in subsequent designs could potentially enhance the slope efficiency to 0.6 mW/mA. Additionally, due to a surface grating fully filled with spin-on-glass (SOG), we obtained a high grating coupling coefficient of 560 cm. The device also demonstrated a SMSR of 50 dB and a thermal resistance of 0.62 K/mW, indicating stable single-mode characteristics and good thermal performance. Using a rectangular oxidation aperture and benzocyclobutene, we achieved a 3-dB modulation bandwidth of 22 GHz at a bias current of 8 mA. Furthermore, with further optimization of parasitic parameters and fabrication, a 3-dB modulation bandwidth of 34 GHz is predicted.
单模表面发射激光器对于新兴的超大规模和超超大规模数据中心至关重要，为高带宽、长距离数据通信系统提供了具有成本效益的解决方案。然而，常用于实现单模表面发射的光栅耦合表面发射激光器，往往存在斜率效率低和阈值高的问题。在本研究中，我们报道了一种高斜率效率的单模表面发射分布反馈激光器，其在二阶光栅区域内具有优化的λ/4相移位置和未泵浦的分布布拉格反射器。λ/4相移相对于二阶光栅的特定位置显著影响二阶光栅与纵向光场之间的相互作用，从而影响其衍射性能。当λ/4相移置于与二阶光栅相邻的一阶光栅蚀刻区域时，我们实现了二阶光栅最高的垂直向上衍射。这种优化使得所制备器件的斜率效率达到0.3 mW/mA。在后续设计中加入底部DBR镜可能会将斜率效率提高到0.6 mW/mA。此外，由于表面光栅完全填充了旋涂玻璃（SOG），我们获得了560 cm的高光栅耦合系数。该器件还展示了50 dB的边模抑制比（SMSR）和0.62 K/mW的热阻，表明具有稳定的单模特性和良好的热性能。使用矩形氧化孔径和苯并环丁烯，我们在8 mA的偏置电流下实现了22 GHz的3 dB调制带宽。此外，通过进一步优化寄生参数和制造工艺，预计3 dB调制带宽可达34 GHz。
