| Summary: | 碩士 === 國立中山大學 === 光電工程學系研究所 === 103 === Nowadays, the development of fiber communication and cloud technology faces a large challenge due to the saturation of signal bandwidth, intriguing the interests for high speed all-optical signal processing in the near future. All-optical signal modulation can enable high speed operation without using traditional RC circuit limitation, reducing power consumption and increasing the flexibility of management in optical network applications. Through the phase modulation in optical signal processing, usage of optical wave interference could lead to large signal-to-noise ratio, high extinction ratio, and low basic power need. Therefore, it is important to study high efficient phase modulation.
In this work, based on quantum confined Stark effect (QCSE), the refractive index- and thus phase- change in quantum well device is studied and used for optical modulation. As an optical power near the bandgap is incident into QW to induce high optical absorption, the built-in electric field from photo-absorption carriers could induce highly nonlinear optical absorption change, thus leading to highly nonlinear optical refractive index change. By exciting another optical wave near the bandgap, the high-efficient phase modulator can thus be expected, leading to all optical modulation.
In my experiment, the direct characteristics of electro-to-optical conversion is first used to examine the refractive index change against with electric field. Through the differential phase-shift keyed (DPSK) demodulator, the optical-to-optical (OO) cross phase modulation can be made to analyze and characterize the phase variation in QW device. Using as short as 350-um long active waveguide, 140 degree phase change is demonstrated.
|
|---|
