Investigation of parameters governing damage resistance of nematic liquid crystals for high-power or peak-intensity laser applications.

We investigate the damage resistance of saturated and unsaturated liquid crystals (LC's) under a wide range of laser excitation conditions, including 1053-nm pulse durations between 600 fs and 1.5 ns and nanosecond pulse excitation at 351 nm and 532 nm. This study explores the relationship between the LC's resistance to laser-induced breakdown (damage) and the electronic structure (π-electron delocalization) of the constituent molecules.

Influence of absorption-edge properties on subpicosecond intrinsic laser-damage threshold at 1053 nm in hafnia and silica monolayers.

Owing to their relatively high resistance to laser-induced damage, hafnia and silica are commonly used in multilayered optical coatings in high-power laser facilities as high- and low-refractive-index materials, respectively. Here, we quantify the laser-induced-damage threshold (LIDT) at 1053 nm in the short-pulse regime of hafnia and silica monolayers deposited by different fabrication methods, including electron-beam evaporation, plasma ion-assisted deposition and ion-assisted deposition. The results demonstrate that nominally identical coatings fabricated by different deposition techniques and/or vendors can exhibit significantly different damage thresholds.

Spectroscopic setup for submicrometer-resolution mapping of low-signal absorption and luminescence using photothermal heterodyne imaging and photon-counting techniques.

A spectroscopic setup that enables the mapping of absorption and photoluminescence with submicrometer spatial resolution and high sensitivity is described. A photothermal heterodyne imaging pump/probe technique is employed for absorption mapping, and low-signal, spatially resolved photoluminescence is recorded using photon counting. High-spatial-resolution mapping is accomplished by using high-numerical-aperture microscope objective focusing laser beams (pump and probe) into a submicrometer spot and raster-scanning sample mounted on the nanopositioning translation stage.

Optical properties of oxygen vacancies in HfO thin films studied by absorption and luminescence spectroscopy.

Hafnium oxide thin films with varying oxygen content were investigated with the goal of finding the optical signature of oxygen vacancies in the film structure. It was found that a reduction of oxygen content in the film leads to changes in both, structural and optical characteristics. Optical absorption spectroscopy, using nanoKelvin calorimetry, revealed an enhanced absorption in the near-ultraviolet (near-UV) and visible wavelength ranges for films with reduced oxygen content, which was attributed to mid-gap electronic states of oxygen vacancies.

Enhanced laser conditioning using temporally shaped pulses.

Laser conditioning was investigated as a function of the temporal shape and duration of 351 nm nanosecond pulses for fused-silica substrates polished via magnetorheological finishing. The aim is to advance our understanding of the dynamics involved to enable improved control of the interaction of laser light with the material to optimize laser conditioning. Gaussian pulses that are temporally truncated at the intensity peak are observed to enhance laser conditioning, in comparison to a Gaussian pulse shape.