1.55 ?m Band Silicon-based ?-? Square Microcavity Quantum Dot Lasers

With the size of micro-electronic devices approaching the physical limit,integrated circuits are restricted by delay and power limitations caused by electrical interconnection.Photon,which is used to replace electron as information carrier,is becoming a pretty desirable alternative to complete the efficient transmission of information.In this way,optical interconnection arose.By integrating photonic devices on the microelectronic circuit chip,the silicon-based optoelectronic integrated circuit get significant achievements.One of the most promising methods for realizing silicon-based lasers is the direct-epitaxial growth of III-V materials on silicon substrates.Meanwhile,the quantum dot(QD)structures can effectively impede the high-density threading dislocations that occur during material growth and greatly improved the working life of lasers.Therefore,QD lasers have become one of the preferred options for silicon-based optoelectronic integration.In addition,the loss of the laser is relatively low in the communication band of 1.31-?m and 1.55-?m,which is beneficial to the fabrication of silicon-based optoelectronic chips.For 1.31-?m band silicon-based lasers,sufficient researches have been done.However,there is still large space for the research of 1.55-?m band silicon-based QD lasers.Compared with the 1.31-?m band,silicon-based optoelectronic chips in 1.55-?m band have lower loss,which is suitable for low loss transmission in mid/long-haul communications,and be compatible with other devices to achieve large-scale integration on silicon substrate.In addition,the square microcavity lasers show a more uniform optical field distribution and less dependence on side wall roughness,which is suitable for coupling with other devices.In recent years,researches of 1.55-?m band square microcavity lasers are mostly focused on InP substrates.However,InP substrates have the disadvantages of small size,high mechanical fragility and high cost,so it is difficult to be applied to large-scale optoelectronic integrated systems.Therefore,it is necessary to analyze 1.55-?m band square microcavity QD lasers based on silicon substrates.Based on the above background,the design and optimization of 1.55-?m band silicon-based square microcavity InAs/InGaAs quantum dot lasers and its integrated structure are studied in this paper.The specific work and research results are as follows:(1)We optimized the structure of silicon-based InAs/InGaAs square microcavity quantum dot laser with an output waveguide.By connecting the output waveguide at the edge-midpoint of the square microcavity,the unidirectional single-mode emission of the laser is realized.At the same time,the emission wavelength is extended to 1.55-?m band by designing a new laser structure.In this structure,the InGaAs nucleation layer is directly epitaxial grown on silicon substrate,it does not require epitaxial growth of InP thin films to fabricate 1.55-?m band silicon-based lasers,which reduces the process complexity and is conducive to silicon-based optoelectronic integration.We analyzed the structure parameters and optical mode of the square microcavity laser.We investigated the parameters that affect the quality factor of the square microcavity,including the side length of the microcavity,the width of the output waveguide,the cladding layer thickness and the etching depth.The results show that with the side length of 16 ?m,the waveguide width of 1.0 ?m,the cladding layer thickness of 1.7 ?m,and the etching depth of 3.95 ?m,the square microcavity laser can achieve the single-mode lasing at the wavelength of 1546.70 nm,with the quality-factor up to 3051.64.(2)We designed the integrated structure based on the cut-corner square microcavity laser and the double-taper-type waveguide.The cut-corner square microcavity laser is connected with the taper-type ?-?waveguide.Then the taper-type ?-? waveguide is further vertically coupled with the taper-type silicon waveguide to realize the unidirectional emission of the cut-corner square microcavity lasers.The coupling structure can be fabricated on silicon-on-insular(SOI)substrate by using the selective area growth method.The results show that when the corner width of the square microcavity laser is 3.5 ?m,the length of the taper-type?-? waveguide is 20 ?m,and the tip width and height of the taper-type silicon waveguide are 0.2 ?m and 0.7 ?m,respectively,the lasing wavelength of the cut-corner square microcavity laser is 1564.71 nm,and the corresponding Q-factor is 1621.05.The coupling efficiency between the cut-corner square microcavity laser and the taper-type ?-? waveguide is 53.5%.