新型高速调制半导体激光器研究

To meet the demand of emerging FTTH and optical interconnect applications, this project will investigate novel low-power consumption, low-cost, high-speed modulated semiconductor lasers, in particular, the new mechanism and structure of the high-speed Q-modulated semiconductor laser. In contrast to conventional electro-absorption or electro-optic modulators placed in the front optical path of the laser output, this monolithically integrated Q modulator is placed at the rear end of the laser.The optical coupling and electrical isolation between the gain and modulator sections are achieved by using deeply etched groove with sub-micron width. By changing the absorption coefficient of the modulator, the quality factor of the laser is modulated, which in turn modulates the threshold and the output power. Since its size can be one order of magnitude smaller than conventional external modulators, it can achieve 40Gb/s or even higher bit rate. It also has small wavelength chirp that can ensure high signal quality after long-distance fiber optic transmission. This new modulation technique can also achieve a high energy conversion efficiency, because the laser does not emit light in the 0 signal state, in contrast to conventional laser-modulator that emits then absorbs the light which results in waste of energy. It does not have the energy waste of ordinary external modulation techniques which inevitablely produce 50% - 75% of the zero signal energy loss. Besides, it does not have any insertion loss. The technique therefore has the important advantage of green energy.

针对新兴的光纤到户、光互连等应用的重要需求，研究新型低能耗、低成本的高速调制半导体激光器，特别是高速Q-调制半导体激光器的新机理结构。与通常置于激光器前端输出光路上的电吸收或电光调制器完全不同，此单片集成Q调制器置于激光器后部，通过亚微米深刻蚀槽实现与增益区的光耦合和电隔离，通过改变调制器吸收系数改变激光器的品质因子，从而改变域值和输出功率。由于它的尺寸可比普通调制器小一个量级，可以实现40Gb/s甚至更高的速率，而且具有啁啾小的特点，可以在光纤中长距离传输而保此高的信号质量。这种新型调制技术还可以实现高能量转换效率，在0信号状态下不发光，而不是象通常调制器在激光发光后再吸收从而造成能量浪费，因而没有普通外调制技术不可避免的50%~75%的零信号能量损耗，而且不存在插入损耗，所以具有绿色节能的重要优点。

针对新兴的光纤到户、光互连等应用的重要需求，本项目研究了高速调制半导体激光器的新机理和新结构，特别是新型高速Q调制半导体激光器以及高速调制可调谐半导体激光器，利用新结构机理来实现低能耗、低成本的高速调制和快速调谐半导体激光器，发展新型半导体激光器的理论、设计、制备和测试技术。在研究过程中，项目组基于行波理论建立了激光谐振腔和Ｑ调制器相互作用的电动力学模型，包括了光波在增益区、调制区以及相位区传播时间对调制响应时间的影响，模拟计算了调制器吸收系数变化对激光腔的品质因子、域值和波长的改变；计算和模拟了高速调制激光器的静态和动态特性，包括激光输出功率随调制器吸收系数的变化、响应速度以及动态波长啁啾特性等。改进设计了多量子阱波导结构，并通过国外合作单位用MOCVD方法生长，制作了带ＤＦＢ光栅的多量子阱材料。在浙江大学建立完善了光刻、湿法腐蚀、氧化硅长膜和干化刻蚀、金属镀膜等工艺，用等离子体深刻蚀方法制作亚微米矩形槽，以电流注入作为调制器吸收系数改变的机理，制作了基于InGaAsP/InP 多量子阱的Q调制DFB激光器和V型腔激光器，进行了实验测试，并进行封装，实现了10Gbps高速调制的V型腔激光发射器件和光收发模块。另外，基于V型腔可调谐半导体激光器和半导体放大器SOA实现了的40Gbps光调制光的高速波长转换器。项目组在Optics Express、IEEE Photonics Journal, IEEE Photonics Technology Letters等SCI期刊上发表了标注项目资助的10篇论文，17篇EI会议论文，申请发明专利7项，培养博士硕士研究生11人，均超过了预期目标。同时，通过与产品化公司合作，成功开发了高速调制且大范围调谐的半导体激光器组件和光收发模块产品。