Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold
The laser-induced damage threshold (LIDT) is widely used as an index for evaluating an optical component’s resistance to laser light. However, a degradation in the performance of an optical component is also caused by continuous irradiation with laser light having an energy density below the LIDT. T...
| Main Authors: | , , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
Beilstein-Institut
2014-08-01
|
| Series: | Beilstein Journal of Nanotechnology |
| Subjects: | |
| Online Access: | https://doi.org/10.3762/bjnano.5.146 |
| _version_ | 1818162272926695424 |
|---|---|
| author | Wataru Nomura Tadashi Kawazoe Takashi Yatsui Makoto Naruse Motoichi Ohtsu |
| author_facet | Wataru Nomura Tadashi Kawazoe Takashi Yatsui Makoto Naruse Motoichi Ohtsu |
| author_sort | Wataru Nomura |
| collection | DOAJ |
| description | The laser-induced damage threshold (LIDT) is widely used as an index for evaluating an optical component’s resistance to laser light. However, a degradation in the performance of an optical component is also caused by continuous irradiation with laser light having an energy density below the LIDT. Therefore, here we focused on the degradation in performance of an optical component caused by continuous irradiation with femtosecond laser light having a low energy density, i.e., laser-induced degradation. We performed an in situ observation and analysis of an increase in scattering light intensity in fused silica substrates. In experiments conducted using a pulsed laser with a wavelength of 800 nm, a pulse width of 160 fs and pulse repetition rate of 1 kHz, we found that the scattered light intensity increased starting from a specific accumulated fluence, namely, that the laser-induced degradation had a threshold. We evaluated the threshold fluence Ft as 6.27 J/cm2 and 9.21 J/cm2 for the fused silica substrates with surface roughnesses of 0.20 nm and 0.13 nm in Ra value, respectively, showing that the threshold decreased as the surface roughness increased. In addition, we found that the reflected light spectrum changed as degradation proceeded. We analyzed the details of the degradation by measuring instantaneous reflectance changes with a pump–probe method; we observed an increase in the generation probability of photogenerated carriers in a degraded silica substrate and a damaged silica substrate and observed a Raman signal originating from a specific molecular structure of silica. From these findings, we concluded that compositional changes in the molecular structure occurred during degradation due to femtosecond laser irradiation having an energy density below the LIDT. |
| first_indexed | 2024-12-11T16:31:02Z |
| format | Article |
| id | doaj.art-27532141ee754f65808f99f7b76e889f |
| institution | Directory Open Access Journal |
| issn | 2190-4286 |
| language | English |
| last_indexed | 2024-12-11T16:31:02Z |
| publishDate | 2014-08-01 |
| publisher | Beilstein-Institut |
| record_format | Article |
| series | Beilstein Journal of Nanotechnology |
| spelling | doaj.art-27532141ee754f65808f99f7b76e889f2022-12-22T00:58:36ZengBeilstein-InstitutBeilstein Journal of Nanotechnology2190-42862014-08-01511334134010.3762/bjnano.5.1462190-4286-5-146Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage thresholdWataru Nomura0Tadashi Kawazoe1Takashi Yatsui2Makoto Naruse3Motoichi Ohtsu4School of Engineering, The University of Tokyo, and The Nanophotonics Research Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8656 Japan,School of Engineering, The University of Tokyo, and The Nanophotonics Research Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8656 Japan,School of Engineering, The University of Tokyo, and The Nanophotonics Research Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8656 Japan,National Institute of Information and Communications Technology, 4-2-1 Nukui-kita, Koganei, Tokyo 184-8795, JapanSchool of Engineering, The University of Tokyo, and The Nanophotonics Research Center, The University of Tokyo, 2-11-16 Yayoi, Bunkyo-ku, Tokyo, 113-8656 Japan,The laser-induced damage threshold (LIDT) is widely used as an index for evaluating an optical component’s resistance to laser light. However, a degradation in the performance of an optical component is also caused by continuous irradiation with laser light having an energy density below the LIDT. Therefore, here we focused on the degradation in performance of an optical component caused by continuous irradiation with femtosecond laser light having a low energy density, i.e., laser-induced degradation. We performed an in situ observation and analysis of an increase in scattering light intensity in fused silica substrates. In experiments conducted using a pulsed laser with a wavelength of 800 nm, a pulse width of 160 fs and pulse repetition rate of 1 kHz, we found that the scattered light intensity increased starting from a specific accumulated fluence, namely, that the laser-induced degradation had a threshold. We evaluated the threshold fluence Ft as 6.27 J/cm2 and 9.21 J/cm2 for the fused silica substrates with surface roughnesses of 0.20 nm and 0.13 nm in Ra value, respectively, showing that the threshold decreased as the surface roughness increased. In addition, we found that the reflected light spectrum changed as degradation proceeded. We analyzed the details of the degradation by measuring instantaneous reflectance changes with a pump–probe method; we observed an increase in the generation probability of photogenerated carriers in a degraded silica substrate and a damaged silica substrate and observed a Raman signal originating from a specific molecular structure of silica. From these findings, we concluded that compositional changes in the molecular structure occurred during degradation due to femtosecond laser irradiation having an energy density below the LIDT.https://doi.org/10.3762/bjnano.5.146compositional change in molecularfemtosecond laserfused silicalaser-induced damagelaser-induced degradation |
| spellingShingle | Wataru Nomura Tadashi Kawazoe Takashi Yatsui Makoto Naruse Motoichi Ohtsu Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold Beilstein Journal of Nanotechnology compositional change in molecular femtosecond laser fused silica laser-induced damage laser-induced degradation |
| title | Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold |
| title_full | Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold |
| title_fullStr | Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold |
| title_full_unstemmed | Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold |
| title_short | Observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser-induced damage threshold |
| title_sort | observation and analysis of structural changes in fused silica by continuous irradiation with femtosecond laser light having an energy density below the laser induced damage threshold |
| topic | compositional change in molecular femtosecond laser fused silica laser-induced damage laser-induced degradation |
| url | https://doi.org/10.3762/bjnano.5.146 |
| work_keys_str_mv | AT watarunomura observationandanalysisofstructuralchangesinfusedsilicabycontinuousirradiationwithfemtosecondlaserlighthavinganenergydensitybelowthelaserinduceddamagethreshold AT tadashikawazoe observationandanalysisofstructuralchangesinfusedsilicabycontinuousirradiationwithfemtosecondlaserlighthavinganenergydensitybelowthelaserinduceddamagethreshold AT takashiyatsui observationandanalysisofstructuralchangesinfusedsilicabycontinuousirradiationwithfemtosecondlaserlighthavinganenergydensitybelowthelaserinduceddamagethreshold AT makotonaruse observationandanalysisofstructuralchangesinfusedsilicabycontinuousirradiationwithfemtosecondlaserlighthavinganenergydensitybelowthelaserinduceddamagethreshold AT motoichiohtsu observationandanalysisofstructuralchangesinfusedsilicabycontinuousirradiationwithfemtosecondlaserlighthavinganenergydensitybelowthelaserinduceddamagethreshold |