Research On Electro-Optic Beam Deflection Based On Lithium Niobate Waveguide With Gradient Width

In optical communication,beam deflection technology plays an important role and is widely used in optical switching,optical detection and ranging(Lidar),space optical communication,optical storage,and many other fields.With the development of communication technology,beam deflection devices are developing in the direction of low power consumption,high integration,large dynamic deflection range,and high angular resolution.At present,the current beam deflection technologies are mainly divided into two categories:mechanical deflection and non-mechanical deflection.Mechanical deflection technology mainly relies on rotating or moving optical elements to achieve large-angle and wavelength-independent beam steering.However,it has shortcomings such as high-power consumption,short life,and slow response time,which can no longer meet the needs of high-speed communication networks.Therefore,a purely electronically controlled nonmechanical technology was born,showing irreplaceable advantages in terms of power consumption and response speed.Existing non-mechanical deflection technologies are mainly based on various principles such as acousto-optic effect,electro-optic effect,thermo-optic effect,and liquid crystal birefringence.Among them,the beam deflection technology based on electro-optic effect has attracted much attention due to its advantages such as fast response speed,high-speed modulation,and no inertial scanning.As an excellent electro-optic crystal,lithium niobate is widely used in electro-optic modulators due to its excellent electro-optic properties(γ33=30.8 pm/V),high Curie temperature(1200 ℃),and mature preparation technology middle.In this paper,we take the future development direction of beam deflectors as the research background and combine with the popular electro-optical material lithium niobate to developing electrooptical deflectors driven with low voltage and high-speed beam steering.And we proposed a high-speed electro-optical deflection device based on the gradient width lithium niobate waveguide and the gradient size isosceles triangle array electrodes.In this paper,the theoretical analysis and experimental test of the proposed electrooptical deflection device are carried out,and the results of the two can show good consistency.The theoretical analysis results show that the isosceles triangular array coplanar electrode of graded size can form a gradient electric field in the lithium niobate waveguide,reshape the beam propagation path,and the appropriate electrode design can realize high-speed single-mode optical field deflection.The experimental results show that the maximum optical field deflection of 25.5 μm and the deflection efficiency of 0.41 μm/V can be achieved by applying a DC voltage ranging from-60 V to 60 V to the 8-80 μm width graded lithium niobate waveguide;the application frequencies are The device exhibits good electro-optical response characteristics under sinusoidal AC voltages of 1 KHz,1 MHz,20 MHz,50 MHz,and 60 MHz,and the response time of the device is 19 ns when a square wave AC voltage of 1 MHz is applied.By further optimizing the waveguide structure and electrode design,the high-frequency performance of the device can be further improved.In addition,we also applied the wavefront shaping technology to the mode control of lithium niobate multimode waveguide for the first time,and verified the feasibility of electro-optical deflection in multimode waveguide through experiments.The input beam is wavefront shaped by a spatial light modulator(SLM),and a focused single-mode light field can be obtained at the end of the waveguide.A single-mode optical field mode deflection efficiency of 0.095 μm/V can be obtained by applying a DC voltage ranging from-32 to 32 V to a 100 μm wide lithium niobate multimode waveguide with direct triangular array electrodes.In conclusion,the electro-optical deflection device design method based on the width graded lithium niobate waveguide and the graded size isosceles triangular array electrodes proposed in this paper has potential application prospects in the fields of lidar,optical switch,laser display,etc.The wavefront shaping technology applied to mode control of multimode waveguide provides a new research direction for beam deflection and more possibilities for the wide application of multimode waveguides.