Ultra-High-Capacity Optical Communications and Networking: III-nitride Wide Bandgap Semiconductors for Optical Communications

该提案是应NSF 01-65“超高容量光通信和网络”的要求提交的。“III族氮化物光电器件提供的好处包括紫外/蓝光发射，能够在非常高的温度和功率水平下工作。GaN/AlGaN或InGaN/AlGaN异质结构的大能带偏移允许新颖的量子阱器件和高发射效率。但目前对Ⅲ族氮化物的研究主要集中在蓝/紫外光电子器件方面。我们提出了一个共同的努力，开发新的光子器件和光子集成电路的基础上III族氮化物宽带隙半导体的光纤通信。高速光开关和波长路由器是必不可少的未来全光网络。目前，硅基阵列波导光栅（AWG）的光机械开关和热调谐还不足以实现光分组交换。另一方面，InP基AWG由于材料的高折射率和小的波导尺寸而具有高的光损耗和温度敏感性，GaN在红外区的折射率约为2.2，这比InP（3.2）更好地匹配光纤的折射率（1.5）。Al-Ga-N和In-Ga-N合金的折射率可控特性使它们成为光波导器件的理想候选材料。这些一起可以允许创建具有前所未有的特性和功能的光子器件。由于III-1氮化物是半导体材料，载流子注入可以用来调制波导的折射率，改变波导的相位延迟。本研究的另一个目的是在光通信窗口中制作电泵浦波导光放大器。目前，InGaAsP基半导体光放大器的载流子寿命仅为亚纳秒级，由于交叉增益饱和快，不适用于WDM光系统。掺铒光纤放大器（EDFA）适用于WDM应用;然而，由于光纤长度的限制，EDFA不可能实现光电集成。III族氮化物半导体似乎能够容纳铒离子。InGaN/GaN异质结构上的电泵浦产生波长约为400 nm的光子，其可用于光学激发铒离子。由于铒在短波长中的吸收效率比目前使用的980 nm或1480 nm的泵浦波长高得多，所以放大器可能做得很短。

This proposal was submitted in response to the solicitation NSF 01-65 on "Ultra-High Capacity Optical Communications and Networking." III-nitride optoelectronic devices offer benefits including UV/blue emission, the ability to operate at very high temperatures and power levels. Large band offsets of GaN/AlGaN or InGaN/AlGaN heterostructures allowing novel quantum well devices, and high emission efficiencies. But the research in III-nitrides has been so far focused on their applications in the blue/UV optoelectronic devices. We propose a combined effort to develop novel photonic components and photonic integrated circuits based on III-nitride wide band gap semiconductors for fiber-optical communications.High-speed optical switches and wavelength routers are indispensable in future all-optical networks. Presently opto-mechnical switches and thermal tuning of silica-based array waveguide gratings (AWG) are not fast enough to perform optical packet switching. On the other hand, InP--based AWGs have high optical loss and temperature sensitivity due to high refractive index of the material and small waveguide size.The refractive index of GaN is about 2.2 in infrared, which is much better matched to the index of optical fiber (1.5) than InP (3.2). The index-controllable nature of Al Ga N and In Ga N alloys makes them an ideal candidate for optical waveguide devices. These together may allow the creation of photonic devices with unprecedented properties and functions. Since Il1-nitrides are semiconductor materials, carrier injection can be used to modulate the refractive index and change the phase delay of the waveguide.Another objective of this research is to make electrically pumped waveguide optical amplifiers in the optical communication windows. Currently, InGaAsP-based semiconductor optical amplifiers have sub-nanosecond carrier lifetime and they are not suitable for WDM optical systems because of the fast cross-gain saturation. Er-doped fiber amplifiers (EDFA) are suitable for WDM applications; however, optoelectronic integration is not possible with EDFAs because of the fiber length. III-nitride semiconductors appear to be able to host erbium ions. Electrical pumping on InGaN/GaN heterostructures generates photons at the wavelength of approximately 400 nm, which can be used to optically excite the erbium ions. Since erbium has much higher absorption efficiency in the short wavelengths than the currently used pumping wavelengths of either 980 nm or 1480 nm, the amplifier may potentially be made very short.