| In recent years,due to the rapid popularization of the network and the rapid development of communication technology,data traffic has shown a trend of rapid growth.In the face of a large amount of data traffic,especially the fast data transmission between data centers,improving the data transmission rate becomes particularly important.Vertical Cavity Surface Emitting Laser(VCSEL)has the characteristics of high modulation rate,small size,low threshold,easy coupling,easy array,good light direction and low cost.It is one of the main light sources for short-distance high-speed optical interconnection.Compared with 850 nm,940 nm VCSEL is less affected by temperature,has lower dispersion,lower transmission loss,higher photodetector sensitivity,and is more safe for eyes.Single-mode VCSEL can obtain longer transmission distance and higher energy efficiency,and it is also more suitable to improve transmission rate through wavelength division multiplexing technology.In this paper,the process preparation and performance test of high-speed singlemode 940 nm VCSEL are studied.The specific contents are as follows:This article introduces the basic concepts of VCSEL,explains the current research background and status of VCSEL.This article summarizes the advantages of current VCSEL,surveys the current research progress of VCSEL,and introduces the application of VCSEL.The theory required for VCSEL is explained,the basic structure of VCSEL is introduced,and the theory of distributed Bragg reflector(DBR)is analyzed and derived.The mechanism and theoretical basis of VCSEL modulation bandwidth are described,and the parameters that affect modulation bandwidth and large signal modulation are analyzed.The preparation process of high speed 940 nm VCSEL was studied.The steps of cleavage,cleaning,photolithography,electrode evaporation and lift-off,ICP etching,wet oxidation,BCB filling and so on were described.Each step was summarized and the points needing attention and possible problems in each step were explained.The process flow of VCSEL preparation was summarized,and the specific process parameters of each step were determined and improved.The study focused on obtaining different oxidation pore sizes by controlling the oxidation parameters,and determined the actual oxidation rate through experiments.VCSEL was successfully prepared.VCSELs of 3 μm,6 μm and 9 μm in oxidation apertures were tested,analyzed,and characterized.The test is divided into four parts.First,the static parameters of the device,including output power,voltage,and mode characteristics,are tested.Through relevant tests,the maximum power of 3 μm VCSEL,6 μm VCSEL and 9 μm VCSEL can reach 2.92 m W,6.79 m W and 10.49 m W respectively.The larger the aperture,the more the VCSEL lasing modes,the side-mode suppression ratio of 3 μm VCSEL can always be greater than 30 d B.Then,the dynamic parameters of the device,including small signal response and data transmission,are tested.Under Small-Signal modulation,the maximum modulation bandwidth of 3 μm VCSEL,6 μm VCSEL and 9 μm VCSEL can reach 27 GHz,23 GHz and 20 GHz respectively.Select the 3 μm VCSEL with the highest modulation bandwidth carries out subsequent data transmission experiments.3μm VCSEL can obtain eye pictures under not return to zero(NRZ)modulation with a maximum transmission rate of 55 Gbit/s.As the aperture of the VCSEL increases,the threshold current gradually increases,but the threshold current density gradually decreases.VCSELs with larger apertures have higher saturation current and power,but lower saturation current density.VCSELs with smaller apertures have better single mode performance,and the mode of lasing gradually increases as the aperture increases.Small aperture VCSEL has higher modulation bandwidth and can also achieve higher transmission rates. |
