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

本提案是应NSF 01-65关于“超大容量光通信和网络”的征集而提交的。III-氮化物光电器件提供的好处包括紫外线/蓝色发射、在非常高的温度和功率水平下运行的能力。GaN/AlGaN或InGaN/AlGaN异质结的大带距允许新的量子阱器件和高发射效率。但到目前为止，对III-氮化物的研究主要集中在它们在蓝/紫外光电子器件中的应用。我们建议共同努力开发基于III-氮化物宽带隙半导体的新型光子元件和光子集成电路，用于光纤通信。高速光开关和波长路由器在未来的全光网络中是不可或缺的。目前，硅基阵列波导光栅(AWG)的光机开关和热调谐速度不足以实现光分组交换。另一方面，由于材料的高折射率和较小的波导尺寸，InP基AWG具有较高的光学损耗和温度敏感性，GaN在红外波段的折射率约为2.2，与光纤的折射率(1.5)比InP(3.2)更匹配。Al-Ga-N和In-Ga-N合金的折射率可控特性使其成为理想的光波导器件。这些结合在一起可能会创造出具有前所未有的特性和功能的光子器件。由于IL1氮化物是半导体材料，因此可以利用载流子注入来调制光波导的折射率和改变其相位延迟。本研究的另一个目的是制作用于光通信窗口的电泵浦光波导光放大器。目前，基于InGaAsP的半导体光放大器具有亚纳秒载流子寿命，由于交叉增益饱和较快，不适合用于WDM光学系统。掺Er光纤放大器(EDFA)适合于WDM应用，但由于光纤长度的限制，与EDFA的光电集成是不可能的。III-氮化物半导体似乎能够容纳铒离子。电泵浦InGaN/GaN异质结产生波长约为400 nm的光子，可用于光学激发Er2+离子。由于Er在短波长的吸收效率比目前使用的980 nm或1480 nm的泵浦波长高得多，因此放大器可能会变得非常短。

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.