2021 Fiscal Year Research-status Report
Investigations of spectrally tunable, nanosecond laser pulse compression characteristics by SBS technique
| Project/Area Number |
21K04934
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| Research Institution | Institute for Laser Technology |
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Principal Investigator |
コスロービアン ハイク 公益財団法人レーザー技術総合研究所, レーザープロセス研究チーム, 副主任研究員 (70291036)
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| Project Period (FY) |
2021-04-01 – 2024-03-31
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| Keywords | SBS; / ns pulse compression; / compact SBS cell; |
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| Outline of Annual Research Achievements |
A variable-length, compact stimulated Brillouin scattering (SBS) amplifier cell was designed. An SBS pulse compressor system was built and tested. FC-72 fluorocarbon liquid was used as an SBS material. A ns Ti:Sapphire laser operating at 15 Hz was employed.
The pulse FWHM before entering the SBS system was 18 ns. With increasing effective length of the SBS cell from 1 to 2 meters (2 - 4 passes) the pulses were compressed from 18 to 8.7 ns. However, the energy conversion efficiency was decreased from 55 % to 30 %. Similar results were obtained also at 780 nm and 820 nm.
The main reason for decreasing conversion efficiency could be the short coherence length of the pump pulses. To increase the efficiency of the SBS pulse compression, pulses with longer coherence length should be used.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
There are several SBS liquids with parameters close to those required for our experiments. The best liquids are FC-40 or FC-70, which have similar characteristics as FC-72 used in present experiments with one exception: their phonon lifetimes are about 0.2 ns or smaller (FC-72 has 1.2 ns phonon lifetime). This roughly means that the pulse compression could be six times or more effective. Unfortunately, due to the supply chain disruption problems, more that 6 months we cannot purchase these SBS liquids.
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| Strategy for Future Research Activity |
In our forthcoming experiments we will reduce the linewidth of the pulses by employing a bandwidth etalon inside the Ti:Sapphire laser resonator. In this way we will increase the coherence length of the pulses and improve both the pulse compression factor and the energy conversion efficiency.
We will also use another Ti:SApphire laser with shorter ns pulses.
We will construct a second harmonics generation (SHG) unit and characterize the frequency doubling properties of the SBS compressed pulses.
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| Causes of Carryover |
We could not purchase SBS liquids (FC-40, FC-70) during the past fiscal year due to the worldwide supply problems. These liquids are used also in semiconductor industry.
We hope to purchase these SBS liquids during this fiscal year and conduct research as originally planned.
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