Two-photon absorption measurements of deep UV transmissible materials at 213  nm

Abstract

We report on two-photon absorption measurements at 213 nm of deep UV transmissible media, including LiF, MgF, CaF, BaF, sapphire (AlO), and high-purity grades of fused-silica (SiO). A high-stability 24 ps Nd:YAG laser operating at the 5th harmonic (213 nm) was used to generate a high-intensity, long-Rayleigh-length Gaussian focus inside the samples. The measurements of the fluoride crystals and sapphire indicate two-photon absorption coefficients between 0.004 and 0.82 cm/GW. We find that different grades of fused silica performed near identically for two-photon absorption; however, there are differences in linear losses associated with purity. A low two-photon absorption cross section is measured for MgF, making it an ideal material for the propagation of high-intensity deep UV lasers.

Deep-UV optical properties of KDP-family crystals: a comprehensive characterization

“…In the measurement of absorption coefficients, two wedged beam splitters (WBSs, wedge angle: 5 degrees) were used to sample the deep-UV laser energy. Since the MgF 2 crystal has a high transmittance and a very weak TPA effect in the deep-UV spectral region, 59 MgF 2 was employed for the material of the WBSs. In addition, to minimize the influence of sampling materials on the results in the measurement process, the reflection scheme of the back surface was adopted to characterize the incident laser energy before the sample, while the laser energy output from the sample was measured by the reflection scheme of the front surface.…”

The LCLS-II Photoinjector Laser Infrastructure

“…The minimum UV power stability is 1% and the minimum point stability is 10 μm. To improve this efficiency, we plan to use higher-quality optical materials [64], as we will introduce in the IIIb subsection. Additionally, we will consider enlarging the beam size on the transport optics to further enhance transmission.…”

“…We expect to achieve long-term high throughput operation without color center formation with Corning 8655, which has a purity of <1ppm of OH content. In the future, we will consider MgF2 and LiF as well [64]. The summarized optics damage tests are shown in Table III.…”

Accurate Determination of the Low-Light-Level Absorption of DUV-Fused Silica at 193 nm with Laser Calorimetry

“…Still, the accurate determination of the internal transmission is difficult, as it is related only to the low-light-level linear absorption or called initial absorption [14]. However, in absorption measurement with LCA, LID or WFS in which an ArF excimer laser is used as the irradiation light source, the measured absorption normally includes the contributions from the surface absorption, the linear absorption, the nonlinear or twophoton absorption, and defect-related absorption [6,15,16]. Some of these contributions are irradiation fluence and repetition rate dependent [17].…”