2020 15th International Conference on Computer Engineering and Systems (ICCES) | 978-0-7381-0559-8/20/$31.00 ©2020 IEEE | DOI: 10.1109/ICCES51560.2020.9334680 Multimode Analysis of High-Speed Multiple- Quantum Well Semiconductor Laser Alaa Mahmoud Laser Institute for Research and Applications (LIRA) Beni-Suef University Beni-Suif, Egypt alaa.abutaleb@lira.bsu.edu.eg Tamer Rizk Department of basic sciences Modern Academy for Computer Science & Management Technology Cairo, Egypt tamerrizk2003@gmail.com Moustafa Ahmed Department of Physics Faculty of Science King Abdulaziz University Jeddah, Saudi Arabia moustafafarghal@yahoo.com Abstract— This paper introduces analysis ofmode dynamics in multiple-quantum well (MQW) laser as a promising device for high-speed photonics. The study is based on a multimode model of semiconductor laser under direct intensity modulation. The simulation results are used to investigate the influence of the injection current on the dynamics of the non-modulated multimode laser, as well as influence ofthe modulation parameters (modulation index and modulation frequency) on the dynamics of the laser. The modal oscillations and the associated multimode hopping that characterizes the long-wavelength laser are investigated in both the non-modulated and modulated laser. The coupling among the oscillating modes under both cases is evaluated in terms oftheir correlation coefficients. Dependence of the small-signal modulation response and bandwidth on the bias current is introduced. In addition, we present comparison of the modulation response of the total output with those of the strongest os cillating mo de s. Keywords— multiple-quantum well; small-signal modulation; hopping; multimode modulation; high-speedphotonics. I. Introduction The current era o f pervasive connectivity or “communication anytime, anywhere, and with anything” o f integrated broadband services has motivated an increasing demand for emerging broadband and high-capacity wireless communications. On the other hand, the continual development in fiber communication systems works to boost the transmission speeds. Integration of fiber optics and wireless radio communication systems has become the most widely used application for increasing the value of the fiber-to-home (FTTH) network using the radio over-fiber (RoF) technology. The demand on such technologies is the availability o f low-cost and high-speed laser with tens- GHz bandwidth. The large differential gain of multiple- quantum-well (MQW) laser diodes motivates thei use as high speed radiation source with large bandwidth [1]. MQW- distributed feedback (DFB) laser emitting at wavelength o f 1.55 gm with 27-GHz bandwidth was demonstrated by Sato et al. [2, 3]. They confirmed possibility o f speeding up the transmission to 40-Gbps over very-short fiber links. Recently, the authors have shown that the increase in laser bandwidth with the rise of the bias current improves the laser modulation efficiency [4]. We also investigated the characteristics o f high-speed 1.55gm MQW laser diodes under both small-signal analog modulation and digital modulation and demonstrated the correlation between them [4]. We reported that the ratio ofthe maximum bit rate to the small-signal bandwidth reaches 1.6 when the modulation index is equal to 0.5. On the other hand, the cost-effectiveness o f the Fabry - Perot (FP) laser diodes makes them widely used as light sources in broader optical network applications. FP-lasers oscillate in a number of longitudinal modes and display asymmetric spectral output when emitting in the C-band o f fiber communications due to mode competition effects [5-8]. In experiments, multimode hopping was observed and attributed to a larger linewidth enhancement factor that enhances asymmetric gain suppression (AGS) and mode coupling [9]. Multimode modeling o f the non-modulated case has shown that the high AGS levels induce hopping multimode oscillation (HMMO) and the laser output is contained in these hopping modes [10]. However, by reducing the AGS and biasing the laser above the threshold current, the laser could show single-mode oscillation (SMO) [10]. The increase in the AGS occurs with an increase in the differential gain and/or the a-factor, and accounts to make the gain spectrum shallow near the central mode [11]. These results were observed experimentally as shown in [9]. inclusion of these multimode effects in the modulation study of these lasers is necessary to understand and control its dynamics. in this work, we extend the single-mode model o f high speed laser dynamics to the case o f multimode oscillations and make a one-to-one correspondence between the induced laser dynamics and the modulation characteristics o f the laser. We 978-0-7381-0559-8/20/$31.00 ©2020 IEEE Authorized licensed use limited to: KING ABDUL AZIZ UNIVERSITY. Downloaded on February 17,2021 at 10:29:03 UTC from IEEE Xplore. Restrictions apply.