Laser and PT-Symmetric Photonics with Organic and Hybrid semiconductors

Open Access
- Author:
- Jia, Yufei
- Graduate Program:
- Electrical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- September 26, 2018
- Committee Members:
- Noel Christopher Giebink, Dissertation Advisor/Co-Advisor
Noel Christopher Giebink, Committee Chair/Co-Chair
Zhiwen Liu, Committee Member
Xingjie Ni, Committee Member
Mikael Caleb Rechtsman, Outside Member - Keywords:
- perovskite
laser
continuous wave
organic materials
parity-time symmetry - Abstract:
- Organic and organic-inorganic hybrid semiconductors have elicited widespread interest demonstrating easy solution processability, wide optical and electrical tunability, and a variety of substrate choices. The impressive optical and electrical properties of organic and hybrid semiconductors make them not only a promising pathway towards next generation optoelectronic devices, but also an excellent platform to explore non-Hermitian photonics. The first part of this thesis focuses on organic-inorganic lead halide perovskite lasers and possible ways to realize room temperature continuous-wave (CW) lasing operation. The second part of the study concerns parity-time symmetry in organic thin film waveguides to explore nonreciprocal light propagation and amplification. The emergence of organic-inorganic lead halide perovskite semiconductors surprised the scientific world as high-efficient low-cost photovoltaics and light emitters. With attractive gain characteristics, perovskite renewed the hope for a tunable, solution-processed laser diode. However, limited lasing lifetime still remains unsolved and blocks perovskite semiconductor lasers from any practical application. With carefully managed heat dissipation and film quality, quasi-continuous-wave (quasi-CW) lasing (MHz repetition rate) with CH3NH3PbI3 (or MAPbI3) distributed feedback lasers can be achieved at tetragonal temperature T = 160 K. We further discover that mixed-phase temperature (130 K < T < 160 K) enables MAPbI3 to provide longtime continuous gain with the help of tetragonal inclusions in orthorhombic bulk film acting loosely as quantum well structure. The success of CW lasing operation in mixed-phase temperature encourages us to study the gain dynamics and lasing death mechanism of MAPbI3 lasers in tetragonal temperature. We identify that heat accumulation and light-induced traps generated by iodine vacancies are most likely the reasons of the limited lasing lifetime at temperatures above T = 160 K, presenting a clear path towards room temperature CW lasing operation. The last part of this work exploits periodic media as an optical platform to study parity-time (PT ) symmetry. PT symmetry can be accomplished in optics with periodic real and imaginary index modulation that transform into one another upon spatial inversion, yielding numerous unusual optical phenomena. A simple approach based on interference lithography and oblique angle deposition is introduced to achieve PT symmetric effective index modulation with large area organic thin film waveguides. Unidirectional reflection of the organic waveguide marks the exceptional point transition to the broken PT phase. Both theoretical and experimental studies of balanced gain and loss integrated in the system provide insight into active PT symmetry.