光电子研究发展中心知识库

光电子器件的小型化、多样化、高性能是实现光电集成的根本要求，也成为光电子器件研究的重要目标。光子晶体特性丰富，以光子晶体为基础的器件表现出传统光电子器件所不具备的性能，如新型的光子晶体激光器、放大器、滤波器、分束器等，具有器件尺寸更小、功耗更低等优异性能，有望成为光电集成的核心器件。慢光效应是光子晶体的重要特性，基于该性能的有源光器件的研究是目前国际上的研究热点之一。利用光子晶体波导结构中的慢光效应可以设计新型的光子晶体光放大器（PCSOA），使得放大器结构紧凑，在小尺寸下实现较大的光学增益。利用完美光子晶体中的带边慢光效应可以设计新型的面发射激光器（PC-SEL），这种器件选用普通波导结构的商用外延片（无DBR复杂外延结构、成本低、成品率高）、无需平面薄层键合等复杂的制作工艺，降低了材料生长、制作工艺给器件制备带来的难度，有望成为未来通讯波段低成本面发射激光器的重要发展方向。

本论文的主要研究内容和创新点为：

1．基于III-V族材料干法刻蚀技术，深入研究了LiNbO₃材料的干法等离子刻蚀技术，实现了LiNbO₃材料的高速干法刻蚀。采用CF₄/Ar对铌酸锂晶体进行感应耦合等离子体干法刻蚀，得到优化的刻蚀条件：CF₄/Ar为30/30 sccm、源功率500 W、偏压功率150 W、腔室压力25 mTorr、衬底温度5 ℃，获得低源功率辐射条件下的最大刻蚀速率196.4 nm/min、LiNbO₃材料与Cr掩膜的选择比高达8.53、获得的图形底面光滑平整、侧墙无沟槽。

2．设计并制作了针对C波段放大的光子晶体光放大器（PCSOA）。光子晶体慢光效应能显著增强光与物质的相互作用，相对于半导体光放大器，器件尺寸缩小20倍以上，在泵浦长度20 μm的情况下，PCSOA实现了12.3 dB的信号增益。基于光子晶体慢光效应的光放大器，可以通过改变光子晶体周期、空气孔半径、慢光波导宽度等，实现不同波长的光放大。

Miniaturization, diversification and high performance of optoelectronic devices are fundamental requirements of achieving optoelectronic integration, and have become an important research goal of optoelectronic devices researches. Photonic crystal devices show many properties, which conventional devices do not have. For example, the lasers, amplifiers, filters and beam splitters based on photonic crystal with smaller device size, lower power consumption and excellent performance, are expected to become the core of optoelectronic integration devices. Slow light effect is an important property of photonic crystals, and the devices based on the slow light effect have attracted more and more attentions. Utilizing the slow light effect in photonic crystal waveguides, a novel photonic crystal semiconductor optical amplifier (PCSOA) can be designed, making SOA with compact structure and relatively large gain in small size. By using band-edge slow light effect in perfect photonic crystal, a novel photonic crystal surface emitting laser (PCSEL) can be achieved with commercial wafer without multilayered distributed Bragg reflector and wafer-bonding technology, reducing the complexity of material grow and fabrication process.

The paper contains the following contents and innovations:

1.      The plasma dry etching of LiNbO₃ is deeply studied basing on the dry etching technology of III-V material and the high rate etching of LiNbO₃ is obtained. The inductively coupled plasma etching (ICP) of LN is taken using CF₄/Ar, and source power, bias power, gas ratio are optimized in the process. The optimized condition is: CF₄/Ar ＝ 30/30 sccm, S.P. = 500 W, B.P. = 150 W, P = 25 mTorr, T = 5 ℃. Under the condition of low source power radiation, we obtain the biggest etching rate of 196.4 nm/min with smooth etching surface and no notch side wall, and the selectivity of LN to Cr is 8.53.

2.      The C-band PCSOA based on photonic crystal slow light effect is designed and fabricated. The slow light effect in photonic crystal can enhance the interaction between light and substance greatly, and with respect to SOA, device dimensions shrink by more than 20 times, which shows the superiorities in the all-optical integration. The highest optical gain of 12.3 dB is obtained in 20 μm pumping length. By changing refractive index, the period of photonic crystal, the radius of air holes and the width of slow light waveguide, the amplification of different wavelengths can be obtained.