OP: Towards Electrically Pumped Perovskite Quantum Dot Lasers

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Photonic integrated circuits with miniature component sizes and high integration density have been regarded as the technology that can potentially provide breakthrough advancement in modern computing and communication systems, as it aims to achieve an optical analogy of VLSI that can overcome several bottleneck electronic technologies encounter such as speed, bandwidth, and power consumption. Key components in photonic integrated circuits include lasers, waveguides, modulators, and photodetectors that can be lithographically defined and fabricated on low-cost Si platforms to achieve ultimate system compatibilities. Among these, lasers have been the most challenging to integrate with Si due to the incompatible fabrication processes between laser gain materials and Si. In addition to computing and optical fiber communications, lasers that feature facile integration on Si can find vast application scopes in free-space communications, projection displays, lighting, spectroscopy, sensing, biomedicine, etc. Wavelength spectra ranging from UV, visible to IR are all desirable depending on the applications. Although heterogeneous optoelectronics based on chip-level bonding and III-V epitaxial growth on Si in bulk, nanowire or quantum dot (QD) forms have been pursued, the fabrication processes are elaborated which is likely to keep the cost high. Solution-processed materials such as organic materials offer a promising route to overcome this challenge as they can be fabricated on a wide variety of substrates, and organic LEDs have achieved impressive performance and are commercially available now. But the material has not been able to achieve laser operations chiefly due to low charge mobility. In recent years, hybrid organic-inorganic halide perovskite materials have emerged as a highly promising newcomer among photonic materials. These materials exhibit high charge mobility, sharp optical absorption edges and high absorption coefficients comparable to GaAs, as well as an unusual defect tolerance. Although lasing in perovskite materials in various resonant-cavity forms have been achieved, perovskite lasers with designed resonant cavities suitable for photonic integrated circuits have not been demonstrated. Furthermore, stability of the perovskite materials is still a main concern in this field, and electrical pumping remains a challenging, overarching goal for perovskite lasers. The objective of the proposed research is to improve and optimize key parameters for achieving electrical pumping in perovskite lasers, and to assess the feasibility of perovskite laser operation under current injection. We will investigate perovskite material properties to improve the charge mobility and material stability. Engineering of the electron and hole transport layers, as well as the device design, will be explored to further enhance the overall device stability. A vertical cavity laser will be designed and fabricated, and optimization of the resonant cavity based on the PI's prior work on optically pumped perovskite QD vertical cavity lasers will be pursued. A waveguide distributed feedback (DFB) laser that can be lithographically defined and fully compatible with Si photonic integrated circuit fabrication will also be explored. These edge-emitting waveguide lasers are expected to achieve lower lasing threshold due to longer gain length and highly confined optical modes. Pulsed current injection with temperature control will be employed to assess the feasibility of electrical pumping. Through the proposed research, key issues for electrically pumped perovskite lasers will be probed and addressed by investigating several aspects of device design and fabrication simultaneously, including material processing, electrical interfaces, optical structures and resonant cavities. The results will contribute to necessary knowledge for realizing electrically pumped perovskite lasers, which provide a promising route to integrated lasers on Si chips.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.