2023 Fiscal Year Research-status Report
| Project/Area Number |
23KJ0553
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| Research Institution | The University of Tokyo |
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Principal Investigator |
REN GUOQI 東京大学, 工学系研究科, 特別研究員(PD)
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| Project Period (FY) |
2023-04-25 – 2025-03-31
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| Keywords | レーザ開発 / レーザ加工 / 微細加工 |
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| Outline of Annual Research Achievements |
The aim of this research is to achieve the precision ultrafast micro processing of semiconductors by inventing a new laser system and controlling the dynamic of excited electrons.
The first step is to develop a novel laser system with a wavelength of 1550 nm. In last year, A narrowband erbium-doped fiber laser oscillator (EDFL) was developed. The mode locked EDFL has an average power of 7.2 mW, a pulse duration of 12 ps at a repetition rate of 50.47 MHz. The spectral bandwidth is 0.37 nm, making it a suitable seeder for the development of a high-average-power master oscillator power amplifier (MOPA) fiber laser system taking advantage of the high SPM during amplification to obtain a broad spectrum and yield sub-ps pulses with a clean temporal profile after pulse compression beyond the power amplifier. Furthermore, a quasi-continuous-wave laser was developed to test the amplification. The output power was 38.24 W with a root mean square instability of 0.19% providing an excellent performance under environmental perturbations. Moreover, the laser had a tunable pulse duration from 2 to 5 μs and a constant pulse energy of 190 μJ.
Besides, through investigating the ultrafast dynamic of ultrafast laser-matter interactions, a new processing method was proposed and experimentally demonstrated in transparent dielectrics, which is expected to be used for other materials.
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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
This research was well conducted as planned in last year. There are mainly two aspects in my research works.
(1) Laser development for novel processing applications: A 200 kHz master oscillator power amplifier erbium-ytterbium-doped fiber laser system was developed. It has a wavelength of 1548.7 nm with a constant pulse energy of 190 μJ providing a tunable pulse duration of 2 to 5 μs. The all-fiber laser system consists of a gain-modulated laser diode used as a seeder, two pre-amplifiers, and a booster amplifier. The output power of the laser system after collimation was 38.24 W, with a root mean square instability of 0.19% providing an excellent performance under environmental perturbations. After synchronization to femtosecond pulses, the obtained μs laser pulses are expected to contribute to novel microprocessing of semiconductors. Besides, a narrowband erbium-doped fiber laser oscillator (EDFL) was developed. The mode locked EDFL has an average power of 7.2 mW, a pulse duration of 12 ps at a repetition rate of 50.47 MHz. The narrow spectral bandwidth of 0.37 nm makes it a suitable seeder for the development of a high-average-power master oscillator power amplifier (MOPA) fiber laser system.
(2) Laser processing: I investigated the ultrafast dynamics of laser-matter interactions, and then proposed a novel method for precision microprocessing without cracks. By using this method, the drilling depth increases more than 3.3 times, and the aspect ratio is improved at least 2.2 times.
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| Strategy for Future Research Activity |
In this year, the research will be conducted from the following aspects.
(1) Laser development: To continue developing the novel laser system. The main work is to amplify the power of the ultrafast laser by using a pre-amplifier and a main amplifier. After the amplification, a Treacy compressor consisting of two transmission gratings is needed to compress the laser pulse to get pulses with a duration of 1 picosecond or even femtosecond.
(2) Laser processing: To precisely measure the electron density in the plasma filament generated by an ultrafast laser pulse, which is of significance for the transient and selective laser processing.
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| Causes of Carryover |
I originally planned to purchase acousto-optic modulators and some gain fiber with a large core diameter for the laser development. However, in the experiment, I found that it is better to order them at the final step of the laser development. Therefore, I will use the left budget in next year together with the new granted funding.
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