以石墨烯薄膜作為飽和吸收體之被動鎖模摻鉺光纖雷射

Abstract

利用化學氣相沉積法製得的多層石墨烯薄膜作為飽和吸收體，可得到穩定1.55 微米波段的被動鎖模雷射輸出。經由光學頻譜分析儀(OSA)得到的摻鉺光纖自發性放大輻射，量測出的石墨烯薄膜飽和吸收體層數為1.33、3.14、3.61、6.96和14.5層；當中，3.14層是由三片近單層石墨烯樣品堆疊而得，而6.96層則為兩片樣品堆疊。 摻鉺光纖雷射的總腔長隨著不同的石墨烯使用於其中而有所不同，範圍從12.4至15.76公尺，經由40/60輸出耦合鏡，波譜寬度、重複頻率和脈衝寬度隨著不同的石墨烯樣品，範圍分別由2.24至4.5奈米 (FWHM)、12.69至16.126兆赫以及1.35至0.627皮秒。雖然樣品堆疊會造成額外的損耗及不穩定並降低調變深度，飽和強度和無線射頻訊雜比皆可被優化。此外，我們亦計算石墨烯的群延遲色散和自相位調變效應。並發現隨著石墨烯的層數變化，群延遲色散和自相位調變效應的變化趨勢是相反的。另外，對於1.33層的石墨稀薄膜，僅15.76公尺的總腔長被利用即得到穩定孤子鎖模輸出。

Stable passively mode locked fiber lasers operated at 1.55 m are demonstrated utilizing multi-layer graphene/PMMA films as SA. The numbers of GSA layers are 1.33, 3.14, 3.61, 6.96 and 14.5 while 3.14 is a three sheets stacked sample and 6.96 is two. The EDFLs with total cavity length from 12.4 to 15.76 m lead to spectral width, repetition rate and pulse duration from about 2.24 to 4.5 nm (FWHM), 12.69 to 16.126 MHz and 1.35 to 0.627 ps. Although stacking sheets arises cavity loss, instability and decreases MD respectively, saturation intensity can be reduced and the signal-to-noise ratio in RF spectrum can be increased. As GSA layers changes, the trends of GDD and phase shift are opposite. The 1.33-layer graphene is used in 15.76 m long cavity length for soliton mode locking.