Liquid Crystal Optical Phased Array (LCOPA) Xiangru Wang， Liang Wu Caidong Xiong, Man Li, Shuanghong Wu Thank~~ Ok，My topic is liquid crystal optical phased array-LCOPA. Corresponding Author Email: xiangruwang@uestc.edu.cn University of Electronic Science and Technology of China INEC 2016, Chengdu

1 2 Outline 3 4 Introduction to LCOPA Principle of LCOPA Our latest milestones 4 Summary Outline My content includes 4 parts, XXXX

Laser beam steering technologies Mechanical 机械式 Bulky, complex, expensive Slow speed Mechanical inertia Acousto-optic 声光 Slow speed Narrow steering range Low efficiency Conventional electro-optic 传统的电光 High driving voltage High insertion loss Narrow steering range

LC Optical Phased Array 液晶光学相控阵 Megapixel Safe, long life, light Mass production Inertialess,no abrasion and vibration Non-Mech Low-cost Pixels Low driving Properties Real-time programmable Agile scan, high precision Low SWaP (size weight and power assumption)

Agile control technology of laser beam! Applications of LCOPA Laser communication Multiple target designation Agile control technology of laser beam! Multi-functional Laser beam combination

Other applications of LCOPA/LCSLM 3D display Wavelength Selective Switch H. Gao et al. in Proc. SID, 2012, 59.4. Robertson, et al. Lightwave Technology 32.3 (2014). There are some other applications of LCOPA, such as 3D display, wavelength selective switch and optical vortices. ['vɔtɪsiz] Switchable and Reconfigurable Optical Vortices Wei Bing, et al. Advanced Materials 26.10 (2014).

1 2 Outline 3 4 Introduction to LCOPA Principle of LCOPA Our milestones 4 Summary Outline Next, I want to make some introduction of the principle of LCOPA.

Principle of optical phased array Principle of LCOPA 1 2 1 2 Physics of LC Phase shifting Principle of optical phased array 液晶移 相原理 光学相 控原理

Liquid Crystal (LC) Liquid crystal is one state between crystalline state and isotropic liquid state in a certain range of temperature. Molecular arrangement have long-range order Relative location between molecules is irregular Anisotropy Fluidity  流动性 各向异性 长程有序性 晶体 各向同性液体

Photoelectrical properties of LC 1.Dielectric anisotropy 介电各向异性 Positive dielectric Anisotropy LC Negative dielectric Anisotropy LC Refractive index ellipsoid 折射率椭球 2. Refractive index anisotropy 折射率各向异性 When light transmission direction parallel to the long axis, polarization direction will not change; When light transmission direction perpendicular to the long axis, polarization direction has biggest change.

Phase-voltage characteristic Physics of LC Phase shifting x z :LC director :Refractive index of extraordinary beam :Refractive index of ordinary beam 液晶指向矢 非寻常光折射率 寻常光折射率 Phase-voltage characteristic curve of device

The sketch of LCOPA For transmissive LCOPA on glass Indium-tin-oxide (ITO) Alignment layer: to pretilt the LC molecules. Spacer: a gap supported by a single layer of spacers with a diameter of a few microns to control the thickness of the LC cell. Sheet electrode: as a common electrode connects to ground. Stripe electrodes: as an array of grating electrodes to apply different voltage on every pixel.

Physics of optical phased array Non-deflected beam Deflected beam （LC director） 0V 0V 0V 0V 5V 3V 2V 0V No driving voltage Driving voltage Incident beam Incident beam

Phase-voltage characteristic The actual work model  Blazed grating Applying voltage Phase-voltage characteristic curve of device LCOPA model

The actual work model FFT

1 2 Outline 3 4 Introduction to LCOPA Principle of LCOPA Our milestones 4 Summary Outline Then, let’s look at some of our milestones on LCOPA.

LCOPA device developments LCoG (liquid crystal on glass) Panel Musk Array size 10mmX10mm Pixels 1X1920 Mode transmission Steering Angle ±6° Diffraction Efficiency (zero-order) 80 - 95% LCOPA

LCoS (liquid crystal on silicon) Future improvements LCoS (liquid crystal on silicon) Properties: Mega-pixels 2-D panel Reflective Low threshold

LCOPA System LCOPA System LC phased array device computer algorithm LC driver

Experimental setup of beam steering LCOPA System LC phased array device computer algorithm LC driver

Beam steering methods of LCOPA 1. variable period grating (VPG) 可变周期光栅 (a) The ideal serrated phase distribution；(b) The discrete phase distribution Steering angle: Uniform and continuous beam deflection with high resolution in the realized steering area.

Beam steering methods of LCOPA 1. variable period grating (VPG) Measured steering angle versus desired angle from 1000μrad to 1400urad from -400μrad to 400μrad Steering steep is 20 urad A linear relationship between measured steering angle and desired steering angle

Beam steering methods of LCOPA Very good repeat precision 1. variable period grating (VPG) Very good repeat precision Smaller than 3 % Measured repetition error versus desired steering angle Measure 30 times of the far-field light spot of the same controlled deflection angle The RMS values of steering angle less than 3% Very good repeat precision

Beam steering methods of LCOPA 2. Sub-aperture coherence(SAC) 子孔径相干 (a) (c) (b)

Beam steering methods of LCOPA 2. Sub-aperture coherence(SAC) More steps Higher precision Intensity distribution of SAC far field on different occupation rates

Beam steering methods of LCOPA 2. Sub-aperture coherence(SAC) Lable Simulation results (urad) Experiment results (urad) Deviation (urad) a 0.0 0.02 1.0 b 1.03 0.89 c 6.25 5.90 0.35 0.78 d 14.75 14.44 0.31 0.68 e 25.00 24.69 0.57 f 31.25 31.54 0.29 0.44 g 37.50 37.89 0.39 0.37 h 43.75 44.81 1.06 0.26 i 50.00 47.68 2.30 0.15 j 49.54 0.46 0.05 k 50.03 0.03 Ultra-high angular resolution less than 5 urad.

1 2 Outline 3 4 Introduction to LCOPA Principle of LCOPA Our milestones 4 Summary Outline

Summary and Future Research LCOPA system Non-mechanical beam steering technology based on liquid crystal material Theoretical study, device and system fabrication LCOPA by LCoS method（liquid crystal on silicon） Beam steering methods of LCOPA VPG method can realize beam deflection with the angular resolution in the order of 20 μrad, and the precision is less than 5 μrad (RMS) SAC method can realize ultra-high angular resolution less than 5 μrad with almost the same precision Performance improvement methods

Thanks to Acknowledgements Prof. Ziqiang Huang Prof. Xiangru Wang & hard working students: Liang Wu,Zhenghui, Guoguo, JingDu, etc &And co-authors: Minggang, Man Li, etc At last, I want to thank xxxx

Thank you for your kind listening!