Research On Sub-wavelength Grating Structure Based On Phase Regulation Characteristics

With the continuous development of semiconductor technology,sub-wavelength gratings have been widely used in the field of optics as an important optical functional component.The sub-wavelength grating is composed of a grating medium?high refractive index material? and an air medium?low refractive index?.The grating period is much smaller than the incident light wavelength,and only zero-order diffraction waves exist,and the high-order diffraction waves are evanescent waves.Therefore,by changing the parameters of the period,duty cycle,thickness and other parameters of the sub-wavelength grating,the wavefront phase regulation of the beam can be realized,thereby realizing the change of optical diffraction characteristics?such as transmission,reflection,polarization splitting,deflection,convergence,etc?.High-performance optical functional devices such as mirrors,transmission mirrors,beam splitter,and deflectors can be prepared by using sub-wavelength gratings,and thus have become a research central issue at domestic and foreign.In this thesis,the sub-wavelength grating based on phase regulation characteristics is studied,which is used to realize the transmission and phase delay function of the beam.The single-focus transmission of the two-wavelength grating and the single-focus transmission of the two-dimensional sub-wavelength grating are obtained through design and simulation.And a bifocal transmission,a gradual wavelength grating phase delay splitter.Finally,an optoelectronic integrated device based on two-dimensional sub-wavelength grating and single-row carrier photo-detector is designed and simulated.The transmission characteristics of the two-dimensional sub-wavelength grating are used to improve the device characteristics of the photo-detector.The main contents of the thesis are as follows:1.The analysis methods of three sub-wavelength gratings are compared,namely Rigorous Coupled Wave Analysis?RCWA?,Finite Element Method?FEM? and Model Method.The rigorous coupled wave method can clearly analyze the diffraction characteristics of light waves on the sub-wavelength grating surface,while the pattern matching method is more suitable for analyzing the effect of light on the sub-wavelength grating;For the numerical calculation of the non-periodic sub-wavelength grating,the finite element analysis method is used to discretize the solution domain of the sub-wavelength grating to simulate the electromagnetic wave interacting with the layered structure of the periodic non-periodic sub-wavelength grating,satisfying each pole.The electromagnetic field boundary conditions are obtained,and the reflection and transmission diffraction efficiencies of the sub-wavelength grating are obtained.2.The transmission effect of one-dimensional strip sub-wavelength grating and two-dimensional block sub-wavelength grating is analyzed and compared.The MATLAB mathematical tool is used to calculate the grating data and the sub-wavelength grating structure is simulated by COMSOL finite element simulation software.The light beam with a working wavelength of 1550nm is incident on the one-dimensional strip-shaped sub-wavelength grating,the beam transmittance is 92.3%,the focal length is 15.1?m,and the extinction ratio is 19.6dB;A beam with a working wavelength of 1550nm is incident on a two-dimensional block-like sub-wavelength grating,and the bulk sub-wavelength grating is arranged at different positions on SiO₂.The focus of the beam convergence is arranged by each block-like sub-wavelength grating and each block the rotation angle of the sub-wavelength grating is determined in common.The beam transmittance is 96.2%,the focal length is 8.3?m,and the extinction ratio is 19.8dB.According to the two-dimensional block sub-wavelength grating,the side-by-side distribution of the two elements is obtained.The dimensional bulk sub-wavelength grating has double-focus points,the transmittance of the concentrated beam is 42.4%and 40.5%,the focal length is 8.02?m,and the extinction ratio is16.2dB and 16dB respectively.3.A gradual wavelength grating phase delay splitter is designed to realize the power sharing of the two left and right beams of the sub-wavelength grating and the phase delay between the two beams.The beam with a working wavelength of 1550nm is incident on the sub-wavelength grating,and the beam is divided into two parts.The left sub-wavelength grating changes the phase of the transmitted light 0,and the right sub-wavelength grating changes the phase shift of the transmitted light to obtain the TM polarization.The ratio of the two optical powers under the light is 1.005:1,the extinction ratio is 19.9dB and 19.8dB,respectively,and the phase between the two beams is ?.4.The two-dimensional sub-wavelength grating with transmission characteristics is used as the light entrance window of the single-row carrier photo-detector.The optoelectronic integrated device?TSGUTC? based on two-dimensional sub-wavelength grating and single-row carrier photo-detector is designed and simulated.The Atlas software simulation shows that under 100W/cm² light intensity,the single-row carrier photo-detector has a DC saturation current of 5.5mA under zero bias,and a quantum efficiency of 59.52%.The bandwidth is 37.7GHz;TSGUTC simulation shows that under the light intensity of 100w/cm²,the DC saturation current is 6mA,the quantum efficiency is 62%,and the bandwidth is 41.3GHz.