Research On 1.55?M GaAs-based Square Microcavity Lasers

At present,the informationization of the society has become a major trend of the development of the society.Information technology and information industry play a more and more important part in promoting social economy and development.In the optical fiber communication system,optoelectronic devices play a key role.Optoelectronic integration technology,which integrates optoelectronic devices and microelectronic devices on one chip,can not only make the chip smaller,but also reduce the power consumption and enhance the property of optical fiber communication system.The InP-based InGaAsP laser is the most widely used in long distance optical fiber communication system.However,the defects of InP substrates,such as high cost,limitation of wafer size and high mechanical fragility,result in the InP-based semiconductor lasers hardly applied in large-scale integrated device.The GaAs substrate is cheaper and play an important role in circuits areas.Consequently,the technology of InP-related long-wavelength semiconductor lasers on GaAs substrates will facilitate the integration of GaAs electronic devices and InP-related optoelectronic devices on GaAs substrates,thus accelerating the progress of optical communication systems and optoelctronic integrated circuit(OEIC).The thesis is aimed at InP-related devices on GaAs substrates,and introduces the material and structure of the 1.55 ?m GaAs-based square microcavity laser.We have investigated the mode characteristics of the resonator and the influence of the related parameters on the whispering gallery mode.The details are listed as follow.1.Design of 1.55 pm GaAs-based square microcavity lasers.The microcavity lasers are constructed on the basis of GaAs-based InGaAs/InGaAsP MQW laser structures.The cavity is laterally surrounded by a benzocyclobutene(BCB)dielectric confinement layer,with 200 nm nitride(SiNx)layer inserted between them.There is a directional output waveguide connected with the cavity at the midpoint of the one side.2.Research on mode characteristics of 1.55 ?m GaAs-based square microcavity lasers.The mode characteristics were numerically investigated by three-dimensional(3D)finite-difference time-domain(FDTD)method for the 1.55 ?m GaAs-based InGaAs/InGaAsP multiple quantum well lasers.It is easy to excite whispering-gallery-like modes around wavelength of 1550 nm for the square microcavities with strong optical confinement in both lateral and vertical directions with the side length from 10?m to 14?m.The mode wavelengths are calculated to be 1549.85 nm,1547.46 nm and 1545.19 nm.The corresponding mode Q factors are 1087.22,1971.30 and 1716.82.These modes can be attributed as TEo,(26,30),TEo,(32,36),and TEo,(38,42).3.Research on the influence of output waveguide width on the microcavity.The results shows that the field intensity coupled into the output waveguide gets stronger and the mode Q factor degrades rapidly with the increase of the waveguide width.And the whispering-gallery-like mode can not be observed when the waveguide width exceeds a quarter of the side length.The resonator suffers less from the narrower output waveguide and the mode Q factors will reach the maximum with the waveguide width of 1.0 ?m.4.Research on the influence of etching-depth on the microcavity.For the cavities with the side length from 10 ?m to 14 ?m,the mode Q factor grows to the maximum and then keep constant with the etching depth increasing from 2.35?m to 3.55 ?m.The high-Q mode can not be observed when the etching depth is less than 2.35 ?m.So the etching depth is set to be 3.55 ?m,the mode Q factor reaches the maximum.