Modeling of Fano Resonance in High-Contrast Resonant Grating Structures

A new model is presented for Fano resonance in resonant grating structure based on the temporal coupled mode theory. By using this model, the reflection spectrum can be reproduced with the information of eigenmode of the structure, which can be numerically calculated by the finite element method. Therefore, the eigenmode plays a key role in determining the profile of the line shape of the Fano resonance in the resonant grating structure. When the space of two grating modulations is decreased, the line shape experiences a significant change. Such a drastic change can be attributed to the increase of quality factor of the eigenmodes. Thus, our model not only provides a simple and intuitive understanding on the mechanism of Fano resonance, but it also offers a convenient way to engineer the line shape of the Fano resonance. The proposed model can be used in many applications, such as biosensors, optical filters, and optical switchers.     

Metamorphic growth of 1.55 μm InGaAs/InGaAsP multiple quantum wells laser structures on GaAs substrates

We fabricate a Ga As-based In Ga As/In Ga As P multiple quantum wells(MQWs) laser at 1.55 μm. Using two-step growth method and thermal cyclic annealing, a thin low-temperature In P layer and a thick In P buffer layer are grown on Ga As substrates by low-pressure metal organic chemical vapor deposition technology. Then, highquality MQWs laser structures are grown on the In P buffer layer. Under quasi-continuous wave(QCW) condition, a threshold current of 476 m A and slope efficiency of 0.15 m W/m A are achieved for a broad area device with 50 μm wide strip and 500 μm long cavity at room-temperature. The peak wavelength of emission spectrum is1549.5 nm at 700 m A. The device is operating for more than 2000 h at room-temperature and 600 mA.