ADVANCED KTN-BASED OPTICAL BEAM DEFLECTORS
Open Access
- Author:
- Zhu, Wenbin
- Graduate Program:
- Electrical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- April 27, 2018
- Committee Members:
- Shizhuo Yin, Dissertation Advisor/Co-Advisor
Shizhuo Yin, Committee Chair/Co-Chair
Victor P Pasko, Committee Member
James Kenneth Breakall, Committee Member
Jian Hsu, Outside Member - Keywords:
- KTN
Beam Deflector
High-speed beam deflector
Multi-denominational beam deflector
Large-aperture beam deflector - Abstract:
- Beam steering systems are widely applied in the areas of 3D printing, 3D imaging, and high-speed bio-imaging systems. All these applications require high-speed high-resolution multi-dimensional beam scanners. Potassium tantalate niobate [KTa1−xNbxO3 (KTN)] crystal-based optical beam deflectors have been widely used in the commercial markets in recent years. In this dissertation, we present a comprehensive study of the working mechanism of KTN beam deflectors and propose new beam deflection mechanisms. To achieve a high-speed KTN beam deflector, we investigate the reason for the responding delay of most KTN-based electro-optical devices. When the operation temperature is above but close to the Curie temperature, the KTN crystal will undergo a phase transition from paraelectric phase to ferroelectric phase with a high external electric field. We find that such field-induced phase transition will limit the responding speed of the KTN-based electro-optical devices. By avoiding the field-induced phase transition, the KTN-based beam deflector can respond in as fast as 10 ns, which is three times faster than the commercial KTN beam scanner. In addition, we combine the composition-gradient-controlled beam deflection and the space-charge-controlled beam deflection in only one piece of KTN crystal to build a two-dimensional beam deflector. In order to realize a 2-D beam deflector, we investigate the coexistence of the space charge and composition gradient in one piece of KTN crystal. If the electric field is parallel to the direction of the composition gradient, the zero-deflection position will shift in the KTN crystal. If the external electric field is perpendicular to the direction of the composition gradient, we can achieve a 2-D beam deflection in the KTN crystal. By adjusting the operating temperature and the driving voltage, we can realize the 2-D beam deflection in one piece of KTN crystal. Moreover, to increase the scanning resolution of the KTN beam deflector, we propose the photon-excitation-enabled KTN beam deflection to enlarge the scanning aperture, further enhancing the scanning resolution. With the photon excitation charging process, we can get a larger charge injection depth and charge density in the KTN crystal. With the help such charging process, we can obtain a larger deflection aperture in the space-charge-controlled beam deflector, and future increase the scanning resolution. Finally, we provide a method to build a low-voltage high-speed KTN beam deflector and propose a method to realize a high-speed wavelength-tunable laser with the KTN beam deflector.