Surface damage induced by micropores in transparent ceramics under nanosecond laser irradiation.

The increasing use of transparent ceramics in laser systems presents a challenge; their low damage threshold has become a significant impediment to the development of powerful laser systems. Consequently, it is imperative to undertake research into the damage sustained by these materials. Micropores, the most common structural defects in transparent ceramics, inevitably remain within the material during its preparation process.

Determining femtosecond laser fluence for surface engineering of transparent conductive thin films by single shot irradiation.

In recent years, there has been increasing interest in optoelectronic applications of transparent conductive oxide (TCO) thin-film-based materials and devices fabricated using patterning techniques. Meanwhile, femtosecond laser processing is a convenient method that further improves the performance of TCO-based functional devices and expands their application prospects. In this study, we proposed a simple and effective strategy to determine the fluences required for laser processing TCOs.

Study on defect-induced damage behaviors of ADP crystals by 355 nm pulsed laser.

High-quality ammonium dihydrogen phosphate (NHHPO, ADP) crystals were grown in Z direction and in defined crystallographic direction (θ=90°, φ=45°) by the rapid growth method, respectively. Defect-induced damage behavior in 355 nm of three types of ADP samples cutting in type-II matching and third harmonic generation direction from the as-grown crystals were investigated, including the initial laser induced damage (LID) characteristics and the physical and chemical properties of defects which serve as the damage precursors. The evaluations of damage behaviors include the "sampling" laser induced damage threshold (LIDT) by 1-on-1 and R-on-1 methods, bulk damage growth and bulk damage morphology.

Laser-damage characteristics of Nd:glass active mirrors.

The active-mirror architecture is widely used in high-power laser systems. In this study, the laser-damage characteristics of Nd:glass active mirrors are investigated. They are exposed to nanosecond 1064 nm laser incident from the Nd:glass.

Method of mitigation laser-damage growth on fused silica surface.

A reliable method, combining femtosecond (fs) laser mitigation and chemical (HF) etching, has been developed to mitigate laser-damage growth sites on a fused silica surface. A rectangular mitigation site was fabricated by an fs laser with a raster scan procedure; HF etching was then used to remove the redeposition material. The results show that the mitigation site exhibits good physical qualities with a smooth bottom and edge.

Investigations on the catastrophic damage in multilayer dielectric films.

HfO2/SiO2 coatings are always fluence-limited by a class of rare catastrophic failures induced by a nanosecond laser with a wavelength of 1053 nm. The catastrophic damage in HfO2/SiO2 coatings behaves as the damage growth with repeated laser irradiation, and thus eventually limits the mirror performance. Understanding the damage processes and mechanisms associated with the catastrophic damage are important for reducing the occurrence of the catastrophic failure and allowing the HfO2/SiO2 coatings to survive at the high fluence required by high laser systems.

Etching of subwavelength periodic stripes by using a nanosecond laser pulse.

In this study, porous silica films, which have particle accumulation microstructure, were prepared using the sol-gel method. For comparison, compact silica films were deposited using the electron-beam-heating method. These films were then irradiated using nanosecond-pulsed laser beams with wavelengths of 1064 and 532 nm.

Femtosecond laser-induced damage of HfO2/SiO2 mirror with different stack structure.

Laser-induced damage of the "standard" (λ/4 stack structure) and "modified" (reduced standing-wave field) HfO(2)/SiO(2) mirrors were investigated by a commercial 800 nm Ti:sapphire laser system. Three kinds of pulse duration of 50 fs, 105 fs, and 135 fs were chosen. The results show that the single-shot damage threshold of the "modified" mirror was about 14%-23% higher compared to that of the "standard" mirror.

Effect of nanosecond laser pre-irradiation on the femtosecond laser-induced damage of Ta2O5/SiO2 high reflector.

The effect of nanosecond laser pre-irradiation on the femtosecond laser-induced damage behaviors of 800 nm 0° AOI Ta(2)O(5)/SiO(2) high reflectors fabricated by e-beam evaporation was explored. Laser pre-irradiation was carried out by Raster-scanning with scanning mode of 1-on-1 and scanning velocities timed such that there was a beam overlap at 70% of the peak fluence, utilizing 5 Hz 1064 nm 12 ns Nd:YAG fundamental lasers. Femtosecond laser damage was investigated by 1 kHz 800 nm 135 fs Ti: sapphire laser system with 1-on-1 mode test.

Characteristics of plasma scalds in multilayer dielectric films.

Plasma scalding is one of the most typical laser damage morphologies induced by a nanosecond laser with a wavelength of 1053 nm in HfO(2)/SiO(2) multilayer films. In this paper, the characteristics of plasma scalds are systematically investigated with multiple methods. The scalding behaves as surface discoloration under a microscope.

Geometrical characteristics and damage morphology of nodules grown from artificial seeds in multilayer coating.

Nodules have been planted in an HfO(2)/SiO(2) multilayer system with absorptive gold nanoparticle seeds located on the surface of a substrate. The topography of nodules was scanned by an atomic force microscope and imaged by a scanning electron microscope. The underlying characteristics of nodules were revealed by a focused ion beam.

Further investigation of the characteristics of nodular defects.

To increase the understanding of the damage sensitivity of nodular defects and provide exact evidence for theoretical study, the structures and the damage behavior of nodular defects in electron-beam deposited mirrors of HfO(2)/SiO(2) are systemically investigated with a double-beam microscope (focused ion beam, scanning electron microscope). Nodular defects are classified into two kinds. In one kind the boundaries between nodules and the surrounding layers have become continuous for the last deposited materials, and in the other there are discontinuous boundaries between nodules and the surrounding layers.

Temperature field analysis of TiO2 films with high-absorptance inclusions.

To deduce the location of absorptive inclusions in thin films, temperature distributions in pure TiO(2) films and TiO(2) films with high-absorptance inclusions are analyzed based on temperature field theory. According to our theoretic simulations, the surface temperature rise increases when absorptive inclusions are incorporated into thin films and shows different values for different inclusions. With the increase of inclusion thickness, the surface temperature rise varies and has a maximum value.

Effect of multiple wavelengths combination on laser-induced damage in multilayer mirrors.

The damage effect of the combined irradiation of 1omega and 3omega in multilayer films was investigated. The experiments were held in both the Laser Induced Damage Threshold (LIDT) mode and the damage probability mode. Moreover, the effect of the laser pre-conditioning was also discussed.

Temperature field analysis of single-layer TiO2 films.

A method is presented to evaluate optical absorption at a random wavelength by calculating temperature distribution in single-layer TiO(2) films. Temperature distribution in single-layer TiO(2) films was analyzed based on temperature field theory. Through our calculations, optical absorption variation was obtained to be similar to that of surface temperature rise in films.