Study On Optical Information Devices By Optofluidics

This dissertation concentrates on the research of the technology of optofluidic variable-focus microlens and the applications in information devices.The fabrication of the integrated device composed of optofluidic variable-focus microlens array,the operation principle of the optofluidic variable-focus microlens and the optical communication devices based on the electro-wetting effect are explored in detail.The main contributions of this dissertation are as follows:1.Young’s equations adapted to cylinder structure is derived based on the Helmholtz free energy minimization method,and a dual-meniscus liquid microlens composed of three kinds of liquid is proposed to overcome the limitation of the focal range of the double-liquid lens.Based on the model of double-liquid lens,the focal length expression of the tri-liquid microlens is deduced using the ray tracing method.2.The relationships of the basic parameters-liquid density,viscosity,surface tension coefficient,liquid oscillation decay time,and lens’ diameter are discussed through the dimension analysis.The electrically controlled oscillatory behavior at the contact of the liquid(meniscus)is studied by introducing the dimensionless liquid oscillation decay time ?(4)and the optical lens parameter Le.Under the condition of choosing or not choosing the kinematics characteristic parameters of the liquid,the two relationships between ?(4)and Le are obtained respectively.Combined with the experimental data,two formulas are presented corresponding to the over-damped lens and the under-damped lens,and exhibits two straight line with slope of 1/2 and 1 in logarithmic coordinates,separately.The equations of the lens’ parameters under optimal operation can be determined by the intersection point of the two lines,offering theoretic guidance for designing and optimizingdevices of the same type.3.The dynamic equations of optofluidic variable-focus microlens are derived from the energy conservation,mass conservation and momentum conservation equations.Algorithmapplicable to two-phase flow in cylinderthrough-hole is chosen to simulate the dynamic characteristics of the specific optofluidic variable-focus microlens.The critic response time of the lens is acquired by analyzing the dependence of the variation of the focus and the parameters of the liquid.The results present good agreement with that of the dimensionless method introduced above.4.Based on the theoretic analysis,various integrated devices composed of optofluidic variable-focus microlens arrays are designed and fabricated.With the specific “conducting substrate/insulating film”structures,the electro-wetting effect on the dielectric surface of the inner core are studied the specific.The technique of the contact angle measurement is optimized.The vertical shooting-diameter measuring method replaces the side shooting-contour extracting-function fitting method to improve the measuring efficiency.The potential distribution and electric field distribution with the variation of frequency of alternate current is simulated under AC control.It turns out that AC control is quite available to modulate the electro-wetting effect.Furtherly,fabrication technology of singlevariable-focusmicrolens is investigated,and the focus variation performances of the variable-focusmicrolens and the variable-focusmicrolens array are tested.5.The behavior of pumpingcapillarydroplet by electro-wetting effect are studied theoretically and experimentally.Electric controlled capillarity phenomena are explained by the microchannel liquid movementtheory.Using the pumping mechanism,opticalswitch waveguide array is proposed,and the performance is tested theoretically and experimentally.The results show an insertion loss lower than 0.27 d Band an extinction ratio higher than 55 d B,and the response time approaches to milliseconds.6.The microprisms based on electro-wetting effect are further discussed theoretically and experimentally,and based on which variable optical attenuator is proposed and optimized.The relationship between the decay control scheme,optical coupling efficiency and thecontrol voltage are explored.Combining the microprisms technology and the tri-liquid microlens,a novel variable optical attenuator model is presented.Additionally,the device is prepared and the performance of light control are validated that,when external voltage varies from 74 V to 53 V,the linear decay range is 2-53 d B.The performancecan meet the most needs of the practical engineering.