Research On 1.3 ?M Silicon-based Quantum Dot Microring Lasers And On-chip Integrated Structures

With the development of communication technology and microelectronics technology,the ever-increasing demand for high-throughput systems has been a major problem for modern data centers and data industries.Silicon-based optical interconnection is considered as one of the most promising methods to realize high-throughput systems due to its advantages of low cost,low power consumption and compatibility with standard CMOS technology.At present,the key to realize optical interconnection on Si substrates is to develop microlasers with low threshold and low power consumption.In recent years,the 1.3-?m silicon-based InAs/GaAs quantum dot lasers have been favored by researchers due to its advantages of long working life,high efficiency and low threshold current.Moreover,compared with hybrid integration,the silicon-based monolithic integration has lower fabrication cost,and can synchronously reduce linewidth with the silicon-based photonic process,which is beneficial to improve the integration density of devices and the reliability of systems.The large-scale development of silicon-based optoelectronic integration also puts forward high requirements on the volume and power consumption of lasers.Whispering-gallery mode microcavity lasers such as microdisk and microring lasers can realize the strong limitation of light by using the total internal reflection effect on the curved boundary,which is conducive to the realization of on-chip integrated light sources with the advantages of low threshold,small volume and high integration density,and it has broad application prospect.However,due to the existence of multiple modes in the whispering-gallery mode microcavity lasers,it is difficult to realize the single-mode lasing.And the strict circular symmetry and the total internal reflection effect of the boundary of the microcavity limit the directional output of light,which cannot meet the optical power of semiconductor lasers in the field of optoelectronic information.Based on the above background,the design and optimization of the 1.3-?m silicon-based monolithic-integrated III-V quantum dot microring laser and its integrated structure are studied in this paper.The specific work and research results are as follows:(1)A 1.3-?m direct epitaxial silicon-based microring laser is proposed,which is connected with a III-V radial waveguide.Through this coupling scheme,the isotropy of light emission in the circular microcavity is broken,and the unidirectional emission characteristics of the microcavity laser are improved.Moreover,the introduction of the inner wall makes the microring cavity have a good suppression effect on multiple modes.Based on the three-dimensional finite-difference time-domain method,the optical modes in the microring laser are analyzed and the material structure and device structure are optimized.It is concluded that when the outer-wall radius of the microring cavity is 3.5?m,the microring width is 1.0 ?m,the cladding thickness is 1.5 ?m,the etching depth is 3.735 ?m and the waveguide width is 0.5?m,the microring laser can achieve the single-mode lasing at the wavelength of 1302.43 nm,with the quality factor of 20093.6 and the optical coupling efficiency between the microring laser and the III-V waveguide is about 47.8%.(2)A multi-wavelength silicon-based microring laser array coupled with tapered Si waveguides is proposed.Multiple microring lasers are arranged in a single line with the same interval.The tapered Si waveguide is aligned with the active region of the laser and there is a certain coupling gap between the microcavity and the Si waveguide.When the microring width is fixed at 1.0 ?m,the effect of the microring radius on the mode wavelength is studied.When the outer-wall radius of the microring is 2.7-3.9?m,the lasing wavelength range is 1289.29?1307.28 nm,with the wavelength intervals of about 3 nm.In addition,the width and thickness of the tapered Si waveguide are optimized numerically.When the widths of the input and output port of the tapered Si waveguide are 1.0 ?m and 0.3 ?m,the waveguide thickness is 0.435 ?m,the taper length is 25 ?m,and the coupling gap is 0.1 ?m,the optical coupling efficiency between the microring laser and the tapered Si waveguide is about 20%,with the outer-wall radius and the microring width of 3.5 ?m and 1.0 ?m.(3)A silicon-based integration scheme based on the notched microring laser and the tapered Si waveguide is proposed.Through the numerical optimization of the notch width,it is concluded that when the outer-wall radius of the microring laser is 3.5 ?m,the ring width is 1.0?m and the notch width is 2.0 ?m,the laser can achieve the single-mode lasing at the wavelength of 1308.86 nm,with the quality factor of 1.9×105.And the laser has good unidirectional emission characteristics along the direction of the notch,with the far-field divergence angle in the plane of 30°.In addition,the influence of the coupling gap between the notched microring laser and the tapered Si waveguide on the optical coupling efficiency is also investigated.The results show that the optical coupling efficiency is about 11.3%when the input port of the tapered Si waveguide is 2.0 ?m,the taper length is 25 ?m,the waveguide thickness is 0.435 ?m and the coupling gap is 0.1 ?m.At the same time,the fundamental mode can be observed at the output port of the Si waveguide with its cross-section size of 435×300 nm.