1.3微米波段兩段式被動鎖模量子點雷射之研究

Abstract

本實驗所採用的樣品，是利用分子束磊晶(Molecule Beam Epitaxy, MBE)在砷化鎵(GaAs)基板成長砷化銦(InAs)自聚性量子點，在室溫下基態雷射波長接近1.3μm，製程以製作脊狀波導(Ridge Waveguide)雷射。並且加入平坦化的步驟，使之具有更好的電流侷限與光侷限的功能。在設計上，以簡易的結構從雷射增益區中分割出一塊吸收區域，用以鎖定特定的模態，從而產生出鎖模脈衝雷射。並對單一被動鎖模量子點雷射元件的脈衝特性做探討，藉由自動化量測系統，調變其吸收區的逆向偏壓與增益區的增益電流，並分析其產生鎖模脈衝的最佳操作條件。再透過不同的吸收區對增益區的分割比例的鎖模量子點雷射，進一步地探討吸收區的大小對鎖模脈衝特性的影響，並產生出寬度為2ps的鎖模脈衝。最後在大幅縮短共振腔長度至1mm下，使被動鎖模量子點雷射產生出頻率超過40GHz的脈衝，其脈衝寬度為3.4ps，可以應用於光通訊與生醫掃描設備上。

In this thesis, two-section passively mode-locked quantum-dot lasers are monolithically fabricated by electrically isolation etching between the gain section and absorber section. As-cleaved cavity lengths of 2 mm and 2.5 mm with gain-to-absorber ratios of 1:5, 1:6 and 1:8 are prepared for the measurement. The spectral and the temporal characteristics of mode-locked pulses investigated as a function of forward bias current in the gain section as well as the reverse bias voltage in the absorber section. To facilitate and fast the measuring process, we have set up the automatic measurement system to retrieve the optical spectra, the electrical RF spectra as well as the autocorrelation traces and analyze them in the systematic mapping. The shortest pulse duration of 2 ps with repetition rate of 16 GHz is achieved in the study. Moreover, we shorten the cavity length down to 1 mm, and successfully demonstrate the mode-locked pulses with repetition rate as high as 41 GHz and duration as low as 3.4 ps. It is possible to apply this high speed and ultra-short pulse laser to optical communication and medical imaging.