We experimentally demonstrated a cascaded internal phase control technique. A laser array with 12 channels was divided into three sub-arrays and a stage array, and phases of the sub-arrays and the stage array were locked by four phase controllers based on the stochastic parallel gradient descent (SPGD) algorithm, respectively. In this way, the phases of the whole array were locked, and the visibility of the interference pattern of the whole emitted laser array in the far field was ∼93%. In addition, the technique has the advantage of element expanding and can be further used in the high-power coherent beam combination (CBC) system due to its compact spatial structure.

介绍了大气湍流效应和热晕效应对列阵合成激光传输特性和光束质量影响的理论研究进展。主要介绍了合成激光在大气中传输的解析和数值模拟研究方法，大气湍流效应对列阵合成光束的光强分布、远场发散角、方向性、曲率半径和湍流距离的影响，以及大气热晕效应对列阵合成光束的光强分布、传输效率、重心偏移、热晕时间尺度和焦移的影响。研究结果表明，大气湍流效应和热晕效应对合成激光光束质量的影响与光束合成方式、合成光束参数以及大气参数密切相关。

主要介绍了近年来光纤激光相控阵相干合成技术的发展现状，总结了中国科学院光电技术研究所在这方面的最新研究成果，包括基于振幅调制的光纤激光相控阵相干合成能力优化、光纤激光相控阵实现收发一体相干合成、光纤激光相控阵的目标在回路相干合成、光纤激光相控阵在大气湍流下实现耦合接收光束的共相合束、基于多孔径波前探测的相干合成方法、基于自适应光纤准直器和微透镜阵列的光束大角度高精度连续寻址扫描等。以上研究工作将促进光纤激光相控阵技术朝向更多单元、更高功率、更远距离等方向演进，并推动其与激光大气传输、空间激光通信、自适应光学等理论和应用的结合与发展。

全光纤激光阵列主动相位控制利用全光纤网络实现阵列激光的活塞相位内部探测与控制，具有结构紧凑、无需外部反馈光学器件和易于扩展等优点，是大阵元规模光纤激光相干合成重要发展方向之一。采用全光纤相位探测结构，介绍了全光纤激光阵列主动相位控制技术的系统原理和利用光纤耦合器实现相位锁定的过程，总结了全光纤激光阵列主动相位控制关键技术，通过优化算法实现全光纤激光阵列主动相位控制验证实验。探讨了在全光纤结构主动相位控制中π相位模糊问题及解决方法，给出了利用双波长探测实现消除π相位模糊问题的仿真结果。最后梳理了全光纤激光阵列主动相位控制研究现状，并从路数扩展、功率提升和应用等方面进行了展望。

半导体激光阵列无输出耦合镜外腔光谱合束技术利用光栅的0级和1级衍射光束反馈实现发光单元的波长锁定，避免了0级和1级衍射光束的转储和浪费，可以获得高的合束效率。因此，0级和1级衍射光束的反馈量高低就会决定外腔波长锁定的稳定性，进而影响合束后光束质量的高低甚至光谱合束的成败。针对此种结构，理论研究了两外腔长度、望远镜滤波结构及 "Smile"效应对0级和1级衍射光束反馈效率的影响，结果表明：（1）外腔长度会影响反馈功率以及串扰程度；（2）望远镜滤波结构可以有效滤除大偏角杂散光束以及使光束正确反馈回原发光单元；（3）"Smile"效应的程度对反馈效率以及输出光束质量影响尤为严重，需要采取措施进行抑制。

In this Letter, we proposed and experimentally demonstrated a directly modulated tunable laser based on the multi-wavelength distributed feedback (DFB) laser array. The lasers are placed in series to avoid the usage of an optical combiner and additional power loss. A three-section design is utilized to reduce the interference from other lasers and improve the electro-optic response bandwidth. Besides, the reconstruction-equivalent-chirp technique is used to simplify the grating fabrication and precisely control the grating phase. We realized 12 channels with 100 GHz spacing with high side mode suppression ratios of above 50 dB. The output power of all the channels is above 14 mW. The 3 dB electro-optic bandwidth is above 20 GHz at a bias current of 100 mA for all four lasers. A 25 Gb/s data transmission over a standard single-mode fiber of up to 10 km is demonstrated for all 12 channels, and 50 Gb/s data per wavelength is obtained through the four-level pulse amplitude modulation. The proposed directly modulated tunable in-series DFB laser array shows the potential for a compact and low-cost light source for wavelength division multiplexing (WDM) systems, such as next-generation front-haul networks and passive optical networks.

A wideband wavelength-tunable 4×5 distributed feedback (DFB) semiconductor laser array based on the reconstruction-equivalent-chirp (REC) technique using a simple tuning scheme is demonstrated. It consists of 20 DFB lasers with 4×5 matrix interleaving distributions, two-level cascaded Y-branch optical combiners, and one active semiconductor optical amplifier (SOA), all in-series integrated on one chip. Unlike the traditional thermal-electric cooler (TEC)-based wavelength-tuning scheme, the tunable 4×5 REC-DFB laser array achieves a faster and broader continuous wavelength-tuning range using TaN thin-film heaters integrated on the AlN submount. By changing the injection current of the TaN resistor from 0 to 190 mA, the proposed tunable laser achieves a wavelength-tuning range of ∼2.5nm per channel and a total tuning of over 50 nm. This study opens up new avenues for realizing cost-effective and wide-tuning-range semiconductor lasers.