Room temperature polariton lasing by current injection into ZnO microcavities

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K14544
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 30010:Crystal engineering-related
• Research Institution: Tohoku University
• Principal Investigator: Shima Kohei 東北大学, 多元物質科学研究所, 准教授 (40805173)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 酸化亜鉛 / 励起子ポラリトン / ポラリトンレーザ

Outline of Final Research Achievements

We aimed to achieve room-temperature electrical pumping in polariton lasers, which are expected to serve as ultra-low-threshold coherent light sources. Firstly, we developed a process to thin down bulk zinc oxide single crystals synthesized via hydrothermal methods to thicknesses on the order of the light wavelength, while ensuring a long exciton lifetime. Secondly, we fabricated optically pumped microcavities and measured the energy dispersion of cavity polaritons' upper and lower branches via angle-resolved reflectance spectroscopy. We confirmed that the Rabi splitting energy, a stability indicator of cavity polaritons, was tens of meV higher than the conventional experimental value (130 meV, low temperature). Thirdly, we manufactured current-injection devices and verified their rectifying characteristics. These achievements are considered significant steps toward stable room-temperature operation of polariton lasers.

Free Research Field

半導体光物性

Academic Significance and Societal Importance of the Research Achievements

本研究で実現されたZnO微小共振器は、励起子ポラリトンの安定性を制限する要因である欠陥および不純物の濃度が従来よりも低いと考えられる。その結果、ポラリトンレーザ発振の閾値励起キャリア密度が低減されると考えられ、最終的には電流注入によるポラリトンレーザ発振に繋がると期待される。ZnOポラリトンレーザは、近紫外線波長域において従来の半導体レーザよりも低い閾値電流密度でコヒーレント光を呈する可能性がある。省エネルギー固体光源として、高演色性白色光源、高密度光情報記録素子、樹脂硬化、スキンセラピー、血液センシングなど、環境・情報・医療などの分野に貢献できる。