Strategies to increase laser damage performance of Ta_2O_5/SiO_2 mirrors by modifications of the top layer design

Schiltz, Drew; Patel, D.; Baumgarten, Cory; Reagan, Brendan; Rocca, J. J.; Menoni, Carmen S.

doi:10.1364/ao.56.00c136

Cited by 16 publications

(5 citation statements)

References 14 publications

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“…Hence, high-resistance optical coatings, various optical coating technologies and large area coating infrastructures have received great attention in recent years. To reach out to the demand for high threshold coatings, a lot of effort has been made to increase the threshold of MLD coatings by specific optical designs, coating methods and optimizing the electric field distribution on the coating surface [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Femtosecond Laser-Induced Damage Characterization of Multilayer Dielectric Coatings

Velpula¹,

Kramer²,

Rus³

2020

Coatings

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The laser-induced damage threshold (LIDT) of optical components is one of the major constraints in developing high-power ultrafast laser systems. Multi-layer dielectric (MLD) coatings-based optical components are key parts of high-power laser systems because of their high damage resistance. Therefore, understanding and characterizing the laser-induced damage of MLD coatings are of paramount importance for developing ultrahigh-intensity laser systems. In this article, we overview the possible femtosecond laser damage mechanisms through damage morphologies in various MLD optical coatings tested in our facility. To evaluate the major contributions to the coating failure, different LIDT test methods (R-on-1, ISO S-on-1 and Raster Scan) were carried out for a high reflective hybrid Ta2O5/HfO2/SiO2 MLD mirror coating at a pulse duration of 37 fs. Different LIDT test methods were compared due to the fact that each test method exposes the different underlying damage mechanisms. For instance, the ISO S-on-1 test at a higher number of laser pulses can bring out the fatigue effects, whereas the Raster Scan method can reveal the non-uniform defect clusters in the optical coating. The measured LIDT values on the sample surface for the tested coating in three test methods are 1.1 J/cm2 (R-on-1), 0.9 J/cm2 (100k-on-1) and 0.6 J/cm2 (Raster Scan) at an angle of incidence of 45 deg. The presented results reveal that the performance of the tested sample is limited by coating defects rather than fatigue effects. Hence, the Raster Scan method is found to be most accurate for the tested coating in evaluating the damage threshold for practical applications. Importantly, this study demonstrates that the testing of different LIDT test protocols is necessary in femtosecond regime to assess the key mechanisms to the coating failure.

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Section: Introductionmentioning

confidence: 99%

Femtosecond Laser-Induced Damage Characterization of Multilayer Dielectric Coatings

Velpula¹,

Kramer²,

Rus³

2020

Coatings

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“…There are strategies to design high reflectors with large bandwidth to support propagation of femtosecond pulses and at the same time increase LIDT. Among these strategies are the use of two high index layer materials in the mirror coating and thickness control in the multilayer design to shift the peak of the standing wave electric field into the low index material in the stack which has higher LIDT [82]. There are opportunities to improve LIDT by exploring new materials, as for example mixtures of SiO 2 or GeO 2 with TiO 2 to selectively design the refractive index to be used as high index material in a multilayer coating.…”

Section: Mirrorsmentioning

confidence: 99%

High average power ultrafast laser technologies for driving future advanced accelerators

Kiani,

Zhou,

Bahk

et al. 2023

J. Inst.

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Large scale laser facilities are needed to advance the energy frontier in high energy physics and accelerator physics. Laser plasma accelerators are core to advanced accelerator concepts aimed at reaching TeV electron electron colliders. In these facilities, intense laser pulses drive plasmas and are used to accelerate electrons to high energies in remarkably short distances. A laser plasma accelerator could in principle reach high energies with an accelerating length that is 1000 times shorter than in conventional RF based accelerators. Notionally, laser driven particle beam energies could scale beyond state of the art conventional accelerators. LPAs have produced multi GeV electron beams in about 20 cm with relative energy spread of about 2 percent, supported by highly developed laser technology. This validates key elements of the US DOE strategy for such accelerators to enable future colliders but extending best results to date to a TeV collider will require lasers with higher average power. While the per pulse energies envisioned for laser driven colliders are achievable with current lasers, low laser repetition rates limit potential collider luminosity. Applications will require rates of kHz to tens of kHz at Joules of energy and high efficiency, and a collider would require about 100 such stages, a leap from current Hz class LPAs. This represents a challenging 1000 fold increase in laser repetition rates beyond current state of the art. This whitepaper describes current research and outlook for candidate laser systems as well as the accompanying broadband and high damage threshold optics needed for driving future advanced accelerators.

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“…[13]. Schiltz et al observed that a modified-electric-field composite low dispersion mirror (E-CLDM) does not offer any definite damage performance advantages over the standard CLDM when tested for a 4 ns source and a 0.19 ns source [11]. However, the reason was not given in his report.…”

Section: Introductionmentioning

confidence: 96%

“…However, reflection bandwidth, dispersion and damage threshold are interdependent, restricting each other [8]. Thereby, the LIDT of broad-bandwidth, low-dispersion mirrors have become a recognized research focus [8][9][10][11][12][13][14][15][16].…”

Section: Introductionmentioning

confidence: 99%

Effect of Electric Field Regulation on Laser Damage of Composite Low-Dispersion Mirrors

Zhang

Wang

et al. 2021

Coatings

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Low dispersion mirrors are important because of their potential use in petawatt (PW) laser systems. The following two methods are known to increase the laser-induced damage threshold of low dispersion optical components: use of a wide-bandgap-material protective layer and control of electric field distribution. By controlling the electric field distribution of composite low-dispersion mirrors (CLDM), we shift the electric field peaks from the material interface into the wide-bandgap material. However, the damage threshold of modified-electric-field composite low dispersion mirror (E-CLDM) does not increase. Damage morphology shows that the initial damaged layer is Ta2O5. An immediate cause is the enhancement of the electric field in internal layers caused by surface electric field regulation. Theoretical calculations show that the damage threshold of CLDM or E-CLDM is determined by the competition results of bandgap and the electric field of layer materials. The CLDM with different materials or different protective layer periods can be optimally designed according to the electric field competition effect in the future.

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Strategies to increase laser damage performance of Ta_2O_5/SiO_2 mirrors by modifications of the top layer design

Cited by 16 publications

References 14 publications

Femtosecond Laser-Induced Damage Characterization of Multilayer Dielectric Coatings

Femtosecond Laser-Induced Damage Characterization of Multilayer Dielectric Coatings

High average power ultrafast laser technologies for driving future advanced accelerators

Effect of Electric Field Regulation on Laser Damage of Composite Low-Dispersion Mirrors

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