| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 100 === Monolithically photonic integration to realize electro-absorption modulated laser (EML) has the advantages of small device area, low cost, low insertion loss, low driving voltage, polarization insensitivity, and high modulation bandwidth, thus is promising for high-speed and long-distance optical communication system. The thesis focuses on the monolithically integration of distributed feedback (DFB) laser and electro-absorption modulator (EAM) on single chip using dual multi-quantum well platform. The dual multi-quantum wells are designed to have different material strains and energy bandgaps for optical gain and optical modulation region, respectively. For device optimization, the multi-quantum well structures are designed using PICS3D software while the optical confinement characteristic in the laser structure is analyzed using FIMMWAVE software. Material absorption coefficient of quantum well set for optical modulation is calculated with Matlab program. The simulation reveals that the optical confinement factor for optical gain and modulation regions are 0.0626 and 0.1855, respectively, while the internal coupling efficiency between two regions is about 88%. The results are then used to calculate the optical extinction ratio and insertion loss of the EAM with different device lengths. Following the aforementioned procedure, we are able to optimize the entire chip parameters in order to achieve an EML capable of providing an optical extinction ratio of >10 dB and a modulation bandwidth of > 10 GHz.
For experimental demonstration, we have successfully fabricated monolithically integrated EML with our optimized dual multi-quantum well configuration. The integrated DFB laser has a threshold current of around 78 mA, a lasing wavelength of 1610 nm, a side-mode suppression ratio of > 50 dB, an electrical contact resistance of 7.3 ohm, and a optical output power of 3 mW. The integrated EAM is biased at around -2 V to allow maximum optical absorption at the wavelengths of around 1.58~1.62 ?慆 and an optical extinction ratio of 18 dB.
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