以啁啾堆疊多層量子點實現波長可調之外腔鎖模雷射二極體

Abstract

本論文利用了啁啾式多層堆疊量子點為雷射主動層，藉由其三種不同量子井覆蓋層厚度堆疊量子點，利用其不同的基態與激發態同時具有增益的特性，得到一個較為寬廣的增益頻譜，在同一共振腔串接增益區與吸收區，做成被動鎖膜元件，並於增益區劈裂鏡面鍍上抗反射鍍層，再借由外腔光柵來調變波長，因吸收率隨波長改變，臨界增益條件也會隨波長而改變，從變波長臨界條件測量中來理解不同波長下變偏壓對吸收率的改變為何，進而討論諧頻鎖模波段與基頻鎖模波段之間的吸收率特性差異。 而利用了啁啾式量子點的光柵耦合波長調變外腔式被動鎖模雷射，在Littrow的光路下，被動鎖模操作下操作電流密度為 1.1kA/cm2波長調變範圍為1200nm至1290nm，1.5kA/cm2範圍為1190nm至1300nm，分別為90nm與110nm，皆連續可調，同時被動鎖模雷射脈衝寬度皆在5至16ps之間，以此相對低操作電流密度下，為目前已知最寬廣的可調變範圍。因其可調範圍寬廣，我們希望從中架設出雙波長鎖模雷射，但在嘗試了雙波長的各種波段組合架設後，發現大多數情形都有以下的現象，在低偏壓時，其吸收率與隨偏壓而改變的情況不同，只能獲得單一波長鎖模。

In this thesis, we used the specially designed Chirped Multilayer Quantum Dot as active layer, expecting to get a broadband gain spectral by simultaneously GS and ES emission of all these three different QW capping layer thickness active layer, then tandem gain and absorption Section in the same cavity, construct a passively mode-locked laser, and so on we coated an anti-reflection coating on the gain side, using external grating as external mirror to achieve wavelength tuning. due to the difference of absorption by different wavelength, the threshold gain will be different by wavelength, in the measurement for threshold current, we can analyzed the absorption differences between wavelength and bias, so we can further discus the absorption differences of harmonic mode-locked and fundamental mode-locked wavelength region. With Littrow configuration constructed Chirp Quantum-Dots Grating coupled external cavity mode-locked laser, when the Tunable range were 1200nm to 1290nm operation current density is 1.1kA/cm2,when 1190nm to 1290nm current density is 1.5kA/cm2, both continuously tunable, pulse width between 5~16ps, this is the broadest wavelength tunable range in this low operation current density so far we know. Due to wide tunable range, we wish to construct double wavelength mode-locked laser, after trying varies of combination of wavelength, due to the variation of absorption condition by changing bias, we found out that we can only have one wavelength mode-lock at double wavelength lasing.