Damage Of Optical Thin Films Research Articles

Study the Damage Effects of Different Laser Pulses on the Pyrotechnic Bridge

lasers are used more and more widely in daily life, medicine and aerospace fields, which promoted the development of all kinds of laser and laser technology. With the continuous breakthroughs in the research field, the application of high power lasers is also more extensive. When the frequency doubling light is emitted from the laser, different wavelengths will act on the separation film simultaneously. Therefore, it is necessary to investigate the damage of optical thin films by laser of single wavelength or multiple wavelengths. The film was irradiated repeatedly by laser aiming, and the damage radius and damage morphology were studied under the action of 1064nm laser and 532nm laser alone and together, as well as the primary and secondary relationship of the damage induced by the two wavelengths. Then, the distribution of explosive damage temperature field was analyzed by simulation. It is concluded that the damage radius at 532nm is larger than that at 1064nm, and the damage depth is deeper. When the two pulses work together, 532nm laser plays a dominant role in the damage process. This study is helpful to better understand the damage mechanism of bridge film and provide reference for the preparation of damage-resistant explosive bridge and laser ignition.

Study the Damage Effects of Different Laser Pulses on the Pyrotechnic Bridge

lasers are used more and more widely in daily life, medicine and aerospace fields, which promoted the development of all kinds of laser and laser technology. With the continuous breakthroughs in the research field, the application of high power lasers is also more extensive. When the frequency doubling light is emitted from the laser, different wavelengths will act on the separation film simultaneously. Therefore, it is necessary to investigate the damage of optical thin films by laser of single wavelength or multiple wavelengths. The film was irradiated repeatedly by laser aiming, and the damage radius and damage morphology were studied under the action of 1064nm laser and 532nm laser alone and together, as well as the primary and secondary relationship of the damage induced by the two wavelengths. Then, the distribution of explosive damage temperature field was analyzed by simulation. It is concluded that the damage radius at 532nm is larger than that at 1064nm, and the damage depth is deeper. When the two pulses work together, 532nm laser plays a dominant role in the damage process. This study is helpful to better understand the damage mechanism of bridge film and provide reference for the preparation of damage-resistant explosive bridge and laser ignition.

Light Field Intensification in Optical Films Induced by Intercoupling of Defects and Organic Contamination.

Based on the finite-difference time-domain method, light field intensification in optical films due to the intercoupling of defects and organic contamination was analyzed. The results show that the intercoupling between the defect and the organic contamination droplet leads to an increase in the local electric field and the coupling effect enhances with the decreasing distance between the defect and the organic contamination droplet and the increasing diameter of the organic contamination droplet. The coupling effect of the defect and the organic contamination layer depends on not only the thickness of the organic contamination layer but also the refractive index of the organic contamination layer. With the thickness and the refractive index of the organic contamination layer increasing, the peak value of the electric field decreases. This work deepens the physical understanding of the degradation mechanism of laser-induced damage in optical thin films used in vacuum.

Material ejection and layer peeling-off in HfO2/SiO2 thin-film beam splitters induced by 1ω and 3ω lasers

Nanosecond pulse laser-induced damage is associated with nodular defects and nano-precursors in hafnium oxide (HfO2)/silica (SiO2) multilayer films. In this study, the dynamic evolution of material ejection and layer peeling-off in HfO2/SiO2 thin-film beam splitters used for third harmonic separation were examined by time-resolved shadowgraph technique under the fundamental frequency of 1064 nm (1ω) and third harmonics 355 nm (3ω) laser beam, respectively. The initial material ejection and subsequent peeling-off of layers were studied to clarify most thin films damage events caused by 1ω and 3ω lasers. The peeling-off of films under 1ω laser was mainly caused by thermomechanical effect. In contrast, the peeling-off of films under 3ω laser was mainly affected by laser-induced mechanical damage. The different transmission forms of layers peeled off from the films revealed the influence of mechanical strength and thermal strength on damage progression. The Taylor–Sedov theoretical model was used to analyze the propagation characteristic shock waves after nanosecond laser irradiation of films. In summary, identification of propagation forms and speed of peeling-off layers provides helpful insights into the damage mechanisms during nanosecond laser-induced damage of optical thin films.

Insight into the degradation mechanism resisting the laser-induced damage of optical films in vacuum by evolution of laser-induced defects

The degradation mechanism resisting the laser-induced damage of optical thin films in a vacuum may be understood by the evolution of laser-induced defects. The accumulation of these newly created defects with irradiated shot numbers results in the severe fatigue effects of multiple-pulse laser damage in the vacuum. The correlative theory was used to further explain this degradation mechanism of multi-pulse irradiation in a vacuum.

Laser-induced damage of optical thin films submitted to 343, 515, and 1030 nm multiple subpicosecond pulses

Optical materials submitted to multiple subpicosecond irradiations are known to exhibit a decrease of the laser-induced damage threshold (LIDT) with the applied number of pulses, an effect referred to as “fatigue” or “incubation.” In this work, we experimentally investigate this effect for the case of optical thin films submitted to multiple exposures with 500 fs pulses at different wavelengths: 1030, 515, and 343 nm. Niobia, hafnia, and silica films made with dense coating techniques (magnetron sputtering, ion-assisted deposition, and reactive low voltage ion plating) are studied, as well as the surface of a fused silica substrate. These samples have been exposed to different pulse numbers (from 1 to 100,000) at a low-frequency repetition rate (less than 1 kHz) and the LIDT has been measured. The results reveal the differences between materials and for the various wavelengths such as the decrease rate of the LIDT or the stabilization level that is reached after multiple exposures. All the results evidence the role of native- and laser-induced defects that we discuss on the basis of published works on the subject.

Transient interference implications on the subpicosecond laser damage of multidielectrics

Laser-induced damage in optical thin films with subpicosecond pulses is investigated. A model dedicated to optical interference coatings and based on the rate equation for free electron generation is introduced. It takes into account the transient interference effects induced by changes in the dielectric function during the laser pulse and its feedback effect on the electron density distribution in the multilayer stack. Simulations are compared to experiments on HfO2 and Ta2O5 films with pulses ranging from 45 fs to 1 ps. It is shown that this approach can improve the interpretation of femtosecond and picosecond laser induced damage in thin films.

The pulsed laser damage sensitivity of optical thin films, thermal conductivity

Pulsed laser induced damage of optical thin films is, in general, initiated by the absorption of laser radiation by imperfections in the films or at interfaces between film layers and/or the substrate. A heat flow analysis of this process stresses the importance that the thermal conductivity of both the thin film host and that of the substrate play in establishing the laser-induced damage threshold. Unfortunately, recent work, which will be reviewed in this presentation, indicates that the thermal conductivity of thin films can be several orders of magnitude lower than that of the corresponding material in bulk form. This situation arises as a consequence of the film structure resulting principally from the deposition process. The importance of thermal conductivity will be compared to parameters such as absorption mechanisms, film materials, composition, and other variables. Its implication for the ultimate optical strength of materials and the direction in which thin film research and processing should proceed will be highlighted.

The role of thermal conductivity in the pulsed laser damage sensitivity of optical thin films

Pulsed-laser-induced damage of optical thin films is, in general, initiated by the absorption of laser radiation by imperfections in the films or at interfaces between film layers and/or the substrate. A heat flow analysis of this process stresses the importance that the thermal conductivity of both the thin film host and the substrate play in establishing the laser-induced damage threshold. Unfortunately, recent work which will be reviewed in this presentation indicates that the thermal conductivity of thin films can be several orders of magnitude lower than that of a corresponding material in bulk form as a consequence of the film structure which results principally from the deposition process. The importance of thermal conductivity will be related to parameters such as absorption mechanisms, film materials, composition and other variables. Its implication for the ultimate optical strength of materials and the direction in which thin film research and processing should proceed will be highlighted.

Defect-induced laser damage of optical thin films

Defect-induced laser damage of optical thin films

Photoacoustic study of laser damage in thin films

We have developed a photoacoustic method that is capable of detecting the occurrence of laser damage in optical thin films and of providing new data about energy transfer processes in the presence of damage.