Research On Design And Application Of Large-Area Electro-Absorption Modulator And Electro-Optical Modulator

Large-area light modulator technology and high-speed photography are always in mutual promotion.In recent years,large-area light modulators have developed raidly in the field of ultrafast diagnostics,3D imaging and free-space optical comunication.They provide a new approach for the realization of high-speed photography in infrared band.In this paper,based on the research of 3DV systems,Naval Research Lab oratory(NRL),Swedish Defence Research Agency(SDRA),Samsung Advanced Institute of Technology(SAIT)and Gwangju Institute of Science and Technology,large-area electro-absorption modulator(EAM)based on quantum confined stark effect(QCSE)applied in 3D imaging system is studied.Because the extinction ratio of large-area QCSE EAM is generally less than lOdB,linear electro-optic crystal is still used in the development of optical switch array in this paper.The main research include:A theoretical model of ranging system based on QCSE EAM is established,and the standard deviation equation of distance measurement is derived.The range error has been investigated with device parameters,such as time constant,extinction ratio and electric absorptivity,as well as timing-error.The results show that the improvement of modulation depth is helpful to improve the measurement accuracy.The measurement error will be difficult to be reduced by increasing the signal-to-noise ratio dominated by shot noise,when the timing accuracy of modulation signal is poor.The main parameters of large-area QCSE EAM with single optical resonance cavity and multi optical resonance cavity,such as operating wavelength,electric absorptivity,extinction ratio,the modulation spectral width and incident angle,are studied by transfer matrix method.A improved reflective structure by optimizing the structure of optical cavity and the front mirror is proposed.The maximum incident angle and spectral width rises to 50° and 7.3nm within which the electric absorptivity is great than 50%.In order to evaluate the influence of polarization characteristics and metal electrode of large-area QCSE EAM on MTF,a vector optical model in descartes coordinate system is proposed based on the concept of Vector Plane Wave Spectrum(VPWS).The influence of diattenuation and retardance of planar optical element on MTF is studied globally and locally within the range of cut-off frequency of optical imaging system(2NA/?).A additional film system is designed to optimize the polarization characteristics to improve the MTF of optical system coupled with large-area QCSE EAM.The influence of opaque p-electrode with different structural parameters on MTF is analysed.A optical switch array with 9-channel is developed in this paper.A installation method using semi-scattering medium and short wave light to implement conoscopic interference is proposed to improve installation accuracy.Optical fiber collimators applied in high-extinction-ratio optical-switch-array is developed.The test result shows that the maximum extinction ratio is greater than 50dB.