Full-silica metamaterial wave plate for high-intensity UV lasers

International audienceBringing light-matter interactions into novel standards of high-energy physics is a major scientific challenge that motivated the funding of ambitious international programs to build high-power laser facilities. The major issue to overcome is to avoid laser intensity heterogeneities over the target that weaken the light-matter interaction strength. Laser beam smoothing aims at homogenizing laser intensities by superimposing on the target laser speckle intensities produced by orthogonal left and right circularly polarized beams. Conventional wave plates based on anisotropic crystals cannot support the laser fluences of such lasers, and the challenge is now to design wave plates exhibiting a high laser induced damage threshold (LIDT). Fused silica exhibits high LIDT, but its isotropic dielectric permittivity prevents effects on polarization retardance. Metamaterials have been widely investigated to tailor the phase and polarization of light but with plasmonic or high-refractive-index materials, and applying this approach with silica is highly challenging due to the weak optical contrast between silica and air or vacuum. Here we design and fabricate a silica-based metasurface acting almost like a quarter-wave plate in the UV spectral range, fulfilling the numerous constraints inherent to highpower laser beamlines, in particular, high LIDT and large sizes. We numerically and experimentally demonstrate that fused silica etched by deep grooves with a period shorter than the wavelength at 351 nm operates the linear-to-quasi circular polarization conversion together with a high transmission efficiency and a high LIDT. The high aspect ratio of the grooves due to the short period imposed by the short wavelength and the deepness of the grooves required to overcome the weak optical contrast between silica and air is experimentally obtained through a CMOS compatible process

Linear-to-circular polarization conversion with full-silica meta-optics to reduce nonlinear effects in high-energy lasers

Abstract High-energy lasers have benefited from intense efforts to bring light-matter interactions to new standards and to achieve laser fusion ignition. One of the main issues to further increasing laser energy is the resistance of optical materials to high laser fluences, in particular at the final stage of the laser beamline where nonlinear Kerr effects can occur in optical materials and provoke laser filamentation. One promising way to mitigate this process is to reduce the nonlinear susceptibility of the material by switching the polarization from a linear to a circular state. Here, we report a significant reduction in the laser filamentation effect on glass by using a full-silica metamaterial waveplateable to switch the linear-to-circular polarization of high fluence laser beams. This result is achieved through the use of a large size full-silica meta-optics exhibiting nominal polarization conversion associated with an excellent transmission efficiency and wavefront quality, as well as a high laser damage resistance

Influence of the multilayer dielectric design on the laser damage resistance of pulse-compression gratings

International audienceMultilayer dielectric (MLD) gratings provide high diffraction efficiency and a high damage threshold. They represent the main solution to compressing a high-power laser beam. However, the laser resistance of MLD gratings limits the power of such facilities. The community devoted a lot of resources to increasing the damage threshold of those components. Today, it is well known that the etching profile plays a key role in the electric field distribution and consequently the laser resistance. In this paper, we focused our optimization on the multilayer dielectric stack to increase the laser-induced damage threshold (LIDT). We numerically and experimentally demonstrated the impact of the MLD stack on the electric field distribution and the LIDT. We manufactured two sets of three samples with identical etching profiles. The calculated electric field intensities were in good agreement with the measured LIDTs. These results demonstrated how to further optimize grating designs through the dielectric stack

Impact of the multilayer dielectric design on the laser-induced damage threshold of pulse compression gratings for petawatt-class lasers

The peak-power of petawatt-class lasers is limited by laser-induced damage to final optical components, especially on the pulse compression gratings. Multilayer Dielectric (MLD) gratings are widely used in compressor systems because they exhibit a high diffraction efficiency and high damage threshold. It is now well established that the etching profile plays a key role in the electric field distribution, which influences the laser damage resistance of MLD gratings. However, less attention has been devoted to the influence of the multilayer design on the laser damage resistance of MLD gratings. In this paper, we numerically and experimentally evidence the impact of the dielectric stack design on the Electric Field Intensity (EFI) and the laser-induced damage threshold (LIDT). Three different MLD gratings are designed and manufactured to perform laser damage tests. On the basis of the expected EFIs and diffraction efficiencies, the measured LIDTs show how the multilayer design influences the laser resistance of the MLD gratings. This result highlights the impact of the multilayer dielectric design on the electric field distribution and shows how to further improve the laser-induced damage threshold of pulse compression gratings

1 Million-Q Optomechanical Microdisk Resonators with Very Large Scale Integration

Cavity optomechanics have become a promising route towards the development of ultrasensitive sensors for a wide range of applications including mass, chemical and biological sensing. We demonstrate the potential of Very Large Scale Integration (VLSI) with state-of-the-art low-loss performance silicon optomechanical microdisks for real-world applications. We report microdisks exhibiting optical Whispering Gallery Modes (WGM) with 1 million quality factors. These high-Q microdisks allow their Brownian motion to be resolved at few 100 MHz in ambient air. Such performance shows our VLSI process is a viable approach for the next generation of high-end sensors operating in vacuum, gas or liquid phase

Sub-20 nm multilayer nanopillar patterning for hybrid SET/CMOS integration

International audienceSETs (Single-Electron-Transistors) arouse growing interest for their very low energy consumption. For future industrialization, it is crucial to show a CMOS-compatible fabrication of SETs, and a key prerequisite is the patterning of sub-20 nm Si Nano-Pillars (NP) with an embedded thin SiO2 layer. In this work, we report the patterning of such multi-layer isolated NP with e-beam lithography combined with a Reactive Ion Etching (RIE) process. The Critical Dimension (CD) uniformity and the robustness of the Process of Reference are evaluated. Characterization methods, either by CD-SEM for the CD, or by TEM cross-section for the NP profile, are compared and discussed

Mid-infrared integrated silicon–germanium ring resonator with high Q-factor

International audienceWe report the realization of a silicon–germanium on silicon ring resonator with high Q-factor at mid-infrared wavelengths. The fabricated ring exhibits a loaded Q-factor of 236 000 at the operating wavelength of 4.18 µm. Considering the combined waveguide propagation losses and bending losses, which are measured to be below 0.2 dB/cm, even higher Q-factors could be achieved on this platform. Furthermore, our dispersion engineering of the waveguides should make these microrings suitable for nonlinear optical applications. These results pave the way for sensing applications and nonlinear optics in the mid-infrared range

Building blocks of silicon photonics

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