High Speed Single Longitudinal Mode Semiconductor Laser Based On Monolithically Integratable Band-pass Filter Structure

The demand of large bandwidth for Internet traffic and access network is increasing rapidly with a variety of applications,such as,cloud computing,4K/8K ultra HD video and virtual reality,etc.Compact,low cost and high performance devices will become the major trend of development for the next-generation ultra-speed optical communication network.Index-coupled distributed feedback(IC-DFB)lasers are widely deployed in current optical communication networks due to their prominent advantage of superior spectral purity,which is extremely beneficial for maintaining the fidelity of signals during the transmission in optical fibers.However,the performance of IC-DFB laser is generally sensible to the external optical feedback.Besides,the other merit of the directly modulated IC-DFB is the accompanying parasitic frequency chirp.Thus,developing cost-effective optical transmitter is a challenging task as fiber dispersion of standard single-mode fiber(SSMF)imposes a severe limit on the system performance with a bit rate over 10 G at C-band.In order to solve the above problems,in this thesis,we have separately proposed two novel single-mode lasers based on the narrow bandwidth band-pass filter structures,i.e.,a narrow-band band-pass filter based single-mode FP laser with significant high immunity to the external optical feedback and a resonant-tunneling band-pass filter based monolithically integrated chirp-managed laser(CML).Moreover,we have proposed an efficient nonlinear carrier distribution approximation based laser simulation method,which can be used to model lasers with severe longitudinal spatial hole burning effect.The main contents and innovations are as follows:1.An efficient nonlinear carrier distribution approximation based laser simulation method has been proposed.The theoretical models for simulating the laser and the proposed filter structure have been established.Specifically including:(1)The threshold,small signal and chirp characteristics of semiconducter lasers are analytically derivated and investigated by using the rate equation model.(2)The time-domain travelling and standing wave model have been built for the laser modelling.These models can clearly describe the coupling of the fields inside the cavity via the grating structure or the device facets,and can also describe the interactions between the fields and the characteristics of waveguide materials,such as,the gain,the loss,and the nonlinearity,etc.The time-domain travelling wave model can be numerically solved by using the split-step method.(3)The transfer matrix method(TMM)with arbitrary incident angle has been applied to calculate the transmission and reflection spectra of the proposed band-pass filter structures.(4)A non-recursive FIR digital filtering technique is applied to cascade the active laser section and the passive band-pass filter section in time-domain simulations.2.A double detuned grating band-pass filter structure has been proposed.By inserting this struture into the conventional FP cavity,a novel high-performance single-mode FP laser has been formed,which has a high immunity to the external optical feedback.The formed transmission and reflection of the double detuned grating structure has been investigated and optimised designed by using the TMM.The proposed single-mode FP laser has been simulated by using the one-dimensional(1D)time-domain travelling wave model and the FIR digital filtering technique.Simulations show that a stable single-mode operation and over a 50 d B SMSR can be obtained.Simulations also show that the proposed singlemode FP laser has a much higher immunity to the external optical feedback,when compared to conventional IC-DFB lasers.3.A resonant-tunelling based double-trench band-pass filter structure has been proposed.The formed transmission spectrum of the aforementioned structure has a super narrow bandwidth,which makes this band-pass filter structure can be applied as the optical spectrum reshaper(OSR)filter,thus realizing the monolithically integrated chirpmanaged laser.The optimum design of the formed transmission spectrum of the aformentioned band-pass filter structure has been carried by using the TMM.The optimum design of the monolithically integrated 1550 nm 25 Gb/s chirp-managed laser has been carried by using the 1D time-domain travelling wave model and the Fouriet transform technique.Simulations show that the proposed device can send 25 Gb/s signal over 22 km on SSMF,and thus is propmising to be applied in the next generation highgeneration high-speed networks,e.g.25 G EPON.