量子點面射型雷射高頻特性之研究

Abstract

本論文旨在研究量子點面射型雷射以及其動態特性的分析。論文分為三個部分，第一個部分，我們提出從雷射的直流特性，包括LIV曲線、發光頻譜圖及其變溫特性。此外也展示此量子點雷射的高頻特性，且展示了2.5Gb/s的眼圖。論文的第二部分，則是利用外部注入鎖定( injection locking )的技術，來改善雷射的高頻特性，包括增進雷射的小信號頻寬，從原本的1.7GHz提升到7.2GHz，並且在7GHz的頻帶載入50Mb/s信號，可以觀測出一個清晰的眼圖。此外，利用注入鎖定技術，可以改善雷射的諧波失真項的特性，從100MHz~1.4GHz都能改善10dB以上。論文的最後，則是利用量子點面射型雷射來當作延遲光行進速度的元件，隨著偏壓電流的不同，可以形成不同延遲的效果，在10GHz的操作之下，可以達到42ps的延遲，我們同時也針對不同輸入信號強度以及不同頻率下的操作，來觀測其延遲的情形。

The thesis studies the fabrication, measurements and the high speed characteristics of quantum dots vertical cavity surface-emitting laser (QD VCSEL). This thesis can be divided into three parts. In the first parts, we present monolithic QD VCSELs operating in the 1.3 μm optical communication wavelength. The QD VCSELs have adapted fully doped structure on GaAs substrate. The output power is ~ 330 μW with slope efficiency of 0.18 W/A at room temperature. Single mode operation was obtained with side-mode suppression ratio of > 30 dB. Modulation bandwidth and eye diagram in 2.5 Gb/s was also presented. In the second part of this thesis, we report the dynamic characteristics of 1.3μm QD VCSEL without and with light injection. The 3 dB frequency response of QD VCSEL based on TO-Can package is enhanced from the free-running 1.75 GHz to 7.44 GHz with the light injection technique. We also report the second harmonic distortion of QD VCSEL with and without external light injection. We observed that the second harmonic distortion of the QD VCSEL with light injection has been suppressed by more than 14 dB. A 50 Mb/s non-return-to-zero (NRZ) pseudo-random binary sequence (PRBS) data with 231 – 1 pattern length from a pattern generator is mixed with a 7 GHz RF carrier and then used to directly modulate the QD VCSEL. The QD VCSEL without light injection cannot generate 7-GHz 50-Mb/s data due to the limited frequency response. With light injection technique, the corresponding eye diagrams can be clearly observed. At the end of this thesis, we experimentally demonstrate tunable slow light in an 1.3 µm QD VCSEL at 10 GHz. Tunable optical group delays are achieved by varying the bias currents, and the maximum delay of 42 ps at 10 GHz has been demonstrated at room temperature.