2017 Fiscal Year Annual Research Report
On-chip plasmonic nanolasers for ultrafast optical interconnects
| Project/Area Number |
17H03229
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| Research Institution | The University of Tokyo |
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Principal Investigator |
J・J Delaunay 東京大学, 大学院工学系研究科(工学部), 准教授 (80376516)
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| Co-Investigator(Kenkyū-buntansha) |
松井 裕章 東京大学, 大学院工学系研究科(工学部), 准教授 (80397752)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | plasmonics / light source / nanostructures |
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| Outline of Annual Research Achievements |
We design and fabricate an on-chip nanolaser using a new plasmonic nanostructure. This research is important because the very efficient light confinement provided by the subwavelength plasmonic nanostructure means that a very low lasing threshold is obtained and a nanosize light circuit no longer limited by diffraction is achieved (compatibility with current electronic devices having 10 nm feature sizes). The fabricated plasmonic nanolaser offers a means to integrate optical nano-circuits directly onto current electronic device chips for ultrafast on-chip optical data processing.
In the first year of this project, we have designed the plasmonic nanostructure and optimized the parameters of the nanostructure by simulation. We have started to build up the setup used in the analysis of the fabricated devices. The active material of the structure was fabricated by pulsed laser deposition. The metal layer was deposited using an ion beam sputtering machine to guarantee high purity of the material and low roughness. Electron beam lithography and subsequent reactive etching were performed to obtain the devices. The fabricated devices were tested with the experimental setup. Lasing was observed at 380 nm in the wavelength from the nanostructures with the size of 150 nm in width and 120 nm in height. The band-width of the lasing is less than 0.3 nm and the threshold of the lasing is 0.16 mJ/cm2. We could not yet confirm lasing of a plasmonic mode (below the diffraction limit of the lasing material, which is about 130 nm in both width and height), but the achieved result is promising.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The design and optimization of the structure have been conducted in time. Also the fabrication technique of the devices was developed and devices could be fabricated in time. Unfortunately, we met two difficult problems with the active material of the device. First, thin films (thickness less than 100 nm) of very high quality of the active material are difficult to obtain. Second, we found that the active material of the device was unstable under some conditions used during the etching step of the fabrication process. We are still optimizing the fabrication conditions of the devices.
Finally, the optical setup used to analyze the performance of the fabricated device could not be completed the first year (we are missing the control of the polarization of the collected light and also need to improve the spatial resolution of the collected light). These improvements will help to obtain results in the second year.
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| Strategy for Future Research Activity |
In the second year of the project, we will focus on the fabrication of the plasmonic nanostructure and the observation of lasing from the fabricated nanostructures.
-The active material used in this project still need to be improved so that the deposition parameters for ZnO deposited by pulsed laser deposition technique will be further investigated. Particularly, high-quality thin film of ZnO on sapphire substrates will targeted.
For the fabrication of the plasmonic nanostructures, deposition of high purity metal will be introduced and the optimization of the parameters for deep reactive ion etching will be conducted. A series of devices with different size will be fabricated so that plasmonic modes can be distinguished from photonic modes (plasmonic modes can only be observed for size below a certain value, which is predicted by simulation. Additionally, the polarization of the emitted light will be measured to confirm the plasmonic modes.
-The setup used to analyze the properties of the fabricated structure is still under construction and require additional effort. Particularly, the control of polarization and spatial resolution of the light collection from the structures will be improved.
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