半導體光放大器之特性研究

本論文主要的重點在於探討使用非對稱多重量子井的彎曲波導的相關特性，包括在不同長度下的發光頻寬特性，架構外腔可調雷射的可調頻寬特性。其中也探討在非對稱多重量子井中增加量子井數目及寬度下的頻寬特性，以及使用未經抗反射鍍膜半導體雷射來架構外腔可調雷射。所使用的彎曲波導元件為直波導連接彎曲波導與傾斜波導所構成，在量測不同長度彎曲波導元件，傾斜波導元件的光電關係曲線以及發光頻譜，我們看到彎曲波導元件兩邊由於反射率不同使得發光特性上有所差異。實驗結果也顯示彎曲波導元件會有共振現象，藉由量測光遠場場型分佈與共振後沿波導方向傳播的雷射頻譜，顯示著共振現象可能是由於光穿出波導而在元件兩端形成共振腔。在探討寬頻發光的量子井結構中，使用七層InGaAsP/InGaAs非對稱多重量子井結構，在電流700mA下有超過300nm的發光頻寬，而在電阻較低且量子井P-side分離侷限異質結構中加入N型delta doping的元件，則在電流400mA下有著超過300nm的發光頻寬，涵蓋了大部分光纖低損耗帶的範圍。以未經抗反射鍍膜的半導體雷射作為外腔可調雷射的增益介質，使用五層量子井結構與七層量子井結構的元件，在低於元件臨界電流下可調頻寬皆超過200nm，而使用彎曲波導元件作為增益介質雖有著臨界電流較大且長度較長下有著元件共振的問題，但在七層量子井五百微米長及五層量子井七百微米長元件仍分別得到了超過250nm及超過230nm的可調頻寬，顯示彎曲波導元件能更有效檢視元件的增益頻寬。

關鍵字

外腔可調雷射；彎曲波導；半導體光放大器；發光頻寬

並列摘要

The bandwidth characteristics of semiconductor optical amplifiers are discussed in this thesis, including spectral width and tuning range of grating external cavity tunable laser. We also discuss the spectral width characteristics when the width of QWs are increased and the number of QWs are added. We use bent waveguide devices instead of AR coating. The bent waveguide devices consist of straight waveguides, bent waveguides and tilt waveguides. First, by measuring L-I curve and emission spectrum, the results show that bent waveguide devices have different characteristics in different facets due to their respective reflectivities. It also shows that bent waveguide device will lase at high injection current or in long device length. We also measure 1-D far-field pattern at different currents and the laser spectrum along different angles. The results show that the resonant cavity in bent waveguide devices may be viewed as two cleaved facets, which function as a F-P laser diode. Using multiple quantum wells consisting of five InGaAs QWs and two InGaAsP QWs, we observe a very broad emission spectrum. The spectral width is over 300nm at current 700mA, covering the range from 1.35μm to 1.55μm. Another similar QW structure but with lower resistance and an additional N type delta dopied in the P-side SCH layer has spectral width over 300nm at 400mA, which covers the most part of low attenuation band of optical fiber. Then we use Fabry-Perot laser diodes without AR-coating as the gain meduim of external cavity tunable laser. The tuning range more than 200nm are obtained both in the laser diodes with 5 QWs structure and 7 QWs structure. When bent waveguide devices are used as the gain meduim, although the threshold currents are larger than F-P lasers, the tuning range can be much broader.

並列關鍵字

external cavity tunable laser ； bent waveguide ； semiconductor optical amplifier ； emission bandwidth

參考文獻

National Taiwan Univ., 2001.

[3] T. E. Stern, and K. Bala, “Multiwavelength optical networks,” Chap. 4, Addison-Weslwy, MA, 1999.

[4] M. Ohstu, “Frequency Control of Semiconductor lasers,” Wiley, New York, 1996.

[5] M. C. Aman and J. Buus, “Tunable Semiconductor lasers,” Astech House, Norwood, MA, 1998.

[6] Jens Buus, “wavelength tunable semiconductor lasers,” TU4B-(2)-1 (Tutorial) P-R CLEO2003.

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半導體光放大器之特性研究

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