서강대학교

초록/요약

This paper has developed an electrically tunable beam deflector using liquid crystals with a wide diffraction angle in a large area. This beam deflector system, which have the high diffraction efficiency and high angular resolution, can steer the incident beam in real-time with wide diffraction angle in a desired direction. The beam deflector system is composed of the beam deflector cell that includes a bottom substrate and the beam deflector driver module which is composed of a control module, a driver board and driver integrated circuits (ICs). An indium-tin-oxide (ITO), a transparent electrode, was used to develop a transmissive type beam deflector. The 2 ㎛ pixel electrode was designed for a wide diffraction angle, which is developed with ITO electrodes using a stepper lithography for active area where actual diffraction occurs. Due to the limited number of control channels in the beam deflector driver module or the beam steering in real-time, a wide diffraction angle and a large area are trade-off relationship. The via-hole and mix-and-match processes were developed and applied to solve the issue of the trade-off relationship. For the via-hole process, the unit bank of the active area which have 720 channels and 1.44 ㎜ × 1.44 ㎜ of the active area was repeated ten times so they were expanded to 7,200 channels and a 14.44 ㎜ × 14.44 ㎜ active area, respectively. Finally, not only the active area for the incident beam is increased but also the diffraction angle is increased. The via-hole process was developed to solve the trade-off between wide diffraction angle and large area due to the limitations in the number of driving channels. The pad with Molybdenum (Mo) electrodes is for the electrical signals of the beam deflector driver module. The electrical signal should be delivered to each ITO electrode in the beam deflector cell. The mix-and-match process was developed to connect between ITO electrodes in the main area and Mo electrodes in the pads area which were developed using the stepper lithography and the mask aligner lithography, respectively. The beam deflector driver module for real-time driving is composed of a control module, a driver board, and driver ICs. The beam deflector driver module with the efficient real-time advanced driving algorithm was developed and applied to the beam deflector system, driving speed is up to 5000 ㎐. The electrically tunable beam deflector using liquid crystals with a wide diffraction angle in large-area is proposed and developed based on the new architecture. The maximum steering angle is 7.643° at a wavelength of 532 ㎚ with high angular resolution accuracy and high diffraction efficiency.