Research On 1.3 ?M High Quality Factor Silicon-based Quantum Dot Microsquare Lasers

Since 1958,the first integrated circuit(IC)chip had been invented.With the rapid development of the IC industry,our society has changed a lot.However,with the integration of the chips are getting more and more complex,the micro-electronic devices are getting closer to their limits for the higher density and smaller scale of the devices.With the problems such as lower transmission band,electrical interconnections have approached their physical limits,and the cost of the device research and production is higher and higher.Such problems surely have hindered the development of the high-end chips.Under the circumstance,on the one hand,traditional electrical interconnection technology has to be updated by the new ones.On the other hand,optical interconnections have the advantages of fast transmission,wide bandwidth and low consumption.Therefore,it is the solution to replace the electrical interconnections with the optical ones.The optical interconnection technology would impulse the progress of the Si-based optical integration,which can also accelerate the speed of the development for the information industry again.The key step of the Si-based optical technology is to combine the advantages of the mature Si-based microelectronic technologies and the optical semiconductor devices with excellent optical characteristics.Silicon,as one of the most well-established and high-yield materials,has the advantage of low cost.Laser sources based on ?-? materials have better optical performances,and microelectronic devices based on silicon are widely used.Thus,there is a need to combine the advantages to achieve?-? laser sources on silicon.Integrating III-V laser sources on silicon is challenging due to the indirect band gap property of silicon.The problems such as the lattice mismatch,the anti-phase boundaries still remain,which will degrade the performances of the devices.In this way,the monolithic growth of ?-? lasers on silicon is crucial,compared with the other growth technologies like wafer-bonding and flip-chip-bonding.The whispering-gallery modes of the optical microcavity have the advantages of small mode value and high quality-factors(Q-factors).It is appropriate to make lasers.The square microcavity has the advantages of well distributed modes,which is comfortable to be connected with output structures and it will accelerate the development of the optoelectronic integrated circuits.The wavelength of 1.3 ?m has a low loss condition.It has become a main working window for the lasers and communication systems.Up to now,in the study of Si-based ?-? microcavity lasers,reports are mainly focused on the process of the material structure,growth technologies and device fabrication.On the contrast,the systematic theoretical researches of Si-based microcavity lasers are less.The Q-factor of the square microcavity is lower,which is necessary to be optimized to achieve the Si-based optical integration.In this paper,the 1.3 ?m Si-based InAs/InGaAs QD square microcavity lasers are researched.the material parameters and device structure are optimized,the optical mode characteristics are numerically analyzed,and the square microcavity is coupled with a directional output waveguide.The study works are listed as follows:(1)We research the side-length of the Si-based square microcavity,which is varying from 10 to 20 ?m by three-dimensional finite-difference time-domain method.When the side-length is increasing from 10 to 14 ?m,the Q-factor increases rabidly.However,at the side-length of 16 ?m,it exhibits a gently drop.Further,after the drop,the Q-factor increases again and the maximum value is obtained at 18 ?m.After the side-length exceeds 18 ?m,the Q-factor decreases rapidly from 18 to 22 ?m.When the side-length is 18 ?m,the Q-factor reaches its maximum.The optimal side-length of the square microcavity is 18 ?m.The optimal Q-factor is 4694.8,which is improved nearly 51%,compared with other research reports.(2)We research the relationship between the etching-depth and Q-factor of the square microcavity.When the etching-depth is varying from 2.5 to 5.0 ?m,the thread of the relation indicates that while increasing the etching-depth of the cavity,the Q-factor is firstly improved.When the etching-depth is 3.5 ?m,the Q-factor achieves the maximum.After the etching-depth is lower than the interface between the Al0.4Ga0.6As cladding layer and the DFLs,the Q-factor remains stable.Hence,the optimal etching-depth of the cavity is studied to be 3.5?m.(3)After connecting the output waveguide with the Si-based square microcavity laser.We research the relationship between the output structures and Q-factor of the square microcavity with the side-length varying from 10 to 20 ?m.With the increase of the waveguide-width,the Q-factor decreases continuously and optical modes of the larger square microcavities are affected more seriously.The field distributions in the cavities are the first-order modes,which are TEo,(34,38),TEo,(39,43),TEo,(48,52),TEo,(56,60),TEo,(64,68),TEo,(70,74),respectively.While the waveguide-width is over 2.0 ?m,the optical modes are not stable and the distributions are distorted.Hence,it is necessary to optimize the output structures.The optimal waveguide-width of the cavity is studied to be 1.0 ?m.