Surface phase defects induced downstream laser intensity modulation in high-power laser facility

Xin, Zhang; Zhou, Wei; Dai, Weizhong; D, Hu; Deng, Xiaotie; Huang, Wanqing; Zhou, Lidan; Yuan, Qiang; Huang, Xiaoxia; Wang, Deen; Yang, Ying

doi:10.1017/hpl.2016.4

Cited by 7 publications

(3 citation statements)

References 12 publications

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“…To this end, herein we employ ultrafast transient absorption (TA) spectroscopy as it offers as traightforwarde xperimental means to track in real-time the charge-carrier dynamics (and hence the charge-transfer direction) in hybrid nanosystems. [3,36,37] Careful analysis of our TA results on the BiOCl(p)/g-C 3 N 4 (n) system (when compared to results measuring the individual components) demonstrates that the photogenerated electrons are transferred from the CB of BiOCl tot hat of g-C 3 N 4 ,n ot in the opposite direction. Moreover,s uch an electron-transfer process was found to occuro n at imescale of afew picoseconds.…”

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confidence: 88%

Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C₃N₄ Photocatalyst by Ultrafast Spectroscopy

2017

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Type‐II heterostructures composed of p‐type BiOCl and n‐type g‐C3N4 have received much attention because of their high efficiencies of charge separation in photocatalysis. However, some ambiguity exists regarding the transfer direction of photogenerated charge carriers in the BiOCl(p)/g‐C3N4(n) system. Although it seems to have not posed an issue in terms of organic photodegradation applications, misinterpretation of the charge‐transfer direction and hence misjudgment of the redox sites in the hybrid system would be a serious problem for other photocatalytic reactions, especially for half reactions, in which the determination of the redox sites is crucial. To solve this problem, we carefully interrogated this topical heterojunction system formed between p‐type BiOCl and n‐type g‐C3N4 by means of ultrafast transient absorption spectroscopy. Our experimental results reveal that the photogenerated electrons are transferred, on a time scale of a few picoseconds, from the conduction band of BiOCl to that of g‐C3N4 and not in the opposite direction. This work enables us to eliminate the ambiguity in using two opposing mechanistic scenarios to describe the p–n heterojunction based photocatalysis mechanism, thereby providing instructive information for the rational design of photocatalytic nanosystems.

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confidence: 88%

Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C₃N₄ Photocatalyst by Ultrafast Spectroscopy

2017

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“…Although the strategy and process for laser damage mitigation on KDP crystal surface have made great progress, the effect of KDP surface mitigation contours upon downstream far-field light modulation is unclear. The downstream light intensity modulation induced by the phase defects that lie on the reflection optics in one of the SG-III laser beamlines was studied by Zhang et al [17] . They found that these surface phased defects result in strong intensity modulation after some propagation distance.…”

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confidence: 99%

Potential damage threats to downstream optics caused by Gaussian mitigation pits on rear KDP surface

Yang

Cheng

Liu

et al. 2020

High Pow Laser Sci Eng

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To determine whether a potassium dihydrogen phosphate (KDP) surface mitigated by micro-milling would potentially threaten downstream optics, we calculated the light-field modulation based on angular spectrum diffraction theory, and performed a laser damage test on downstream fused silica. The results showed that the downstream light intensification caused by a Gaussian mitigation pit of 800 μm width and 10 μm depth reached a peak value near the KDP rear surface, decreased sharply afterward, and eventually kept stable with the increase in downstream distance. The solved peak value of light intensification exceeded 6 in a range 8–19 mm downstream from the KDP rear surface, which is the most dangerous for downstream optics. Laser damage sites were then induced on the fused silica surface in subsequent laser damage tests. When the distance downstream was greater than 44 mm with a downstream light intensification of less than 3, there were no potential damage threats to downstream optics. The study proves that a mitigated KDP surface can cause laser damage to downstream optical components, to which attention should be paid in an actual application. Through this work, we find that the current manufacturing process and the mitigation index still need to be improved. The research methods and calculation models are also of great reference significance for related studies like optics mitigation and laser damage.

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“…The SCBHD was shown to be better than both. We furthermore proposed an improved setup to detect phase variation, by replacing the ordinary beam splitter (BS) with a polarization one, which is essential for large optics in high-power lasers and is related to the wavefront, damage threshold, and other parameters [16][17][18] .…”

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Transmittance and phase measurement via self-calibrated balanced heterodyne detection

et al. 2018

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It is rare for a conventional direct detection method to measure the transmittance uniformity of mirrors with rigorous standards, especially to meet the requirement of transmittance/reflectance and phase detection simultaneously. In this study, a new method of self-calibrated balanced heterodyne detection (SCBHD) is proposed. It can be self-calibrated by a two-channel structure to overcome the environmental effects in large optics scanning detection by employing highly accurate heterodyne interference. A typical transmittance measurement experiment was performed at 1053 nm wavelength via SCBHD. A standard deviation (SD) of 0.038% was achieved in the preliminary experiment. The experimental results prove to reduce the SD by approximately two orders of magnitude compared with the conventional direct detection method in the same condition. The proposed method was verified as being promising not only for its wider dynamic measurement range and its higher accuracy but also for its simultaneous transmittance and phase detection ability.

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Surface phase defects induced downstream laser intensity modulation in high-power laser facility

Cited by 7 publications

References 12 publications

Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C₃N₄ Photocatalyst by Ultrafast Spectroscopy

Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C₃N₄ Photocatalyst by Ultrafast Spectroscopy

Potential damage threats to downstream optics caused by Gaussian mitigation pits on rear KDP surface

Transmittance and phase measurement via self-calibrated balanced heterodyne detection

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Surface phase defects induced downstream laser intensity modulation in high-power laser facility

Cited by 7 publications

References 12 publications

Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C3N4 Photocatalyst by Ultrafast Spectroscopy

Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C3N4 Photocatalyst by Ultrafast Spectroscopy

Potential damage threats to downstream optics caused by Gaussian mitigation pits on rear KDP surface

Transmittance and phase measurement via self-calibrated balanced heterodyne detection

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Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C₃N₄ Photocatalyst by Ultrafast Spectroscopy

Determining the Charge‐Transfer Direction in a p–n Heterojunction BiOCl/g‐C₃N₄ Photocatalyst by Ultrafast Spectroscopy