Laser Induced Contamination (LIC) is one of the major issues in high energy high repetition rate laser systems. The growth of contamination during the operation of the laser influences the components spectral performance and can lead to the catastrophic damage. Several previous investigations indicate that LIC growth depends on the coatings material and even its deposition method. In our work, we investigate electron-beam deposited HR mirrors for the wavelength of 800 nm. Three different designs were tested in vacuum conditions under high repetition and high energy laser irradiation using femtosecond pulses. Two of the designs are based on quarter wavelength optical thickness (QWOT) layers: last layer of the first mirror is high refractive index film, hafnia in our case, and for the second mirrors the last layer was double QWOT of low refractive index film, silica in our case. For the last coating the E-field was modified by changing the last silica layer thickness. All samples were irradiated below the damage threshold level and LIC observed under confocal microscope. Analysis were obtained by comparing the influence of the last layer and E-field distribution within the multilayer coatings. Conclusions and recommendations for LIC reduction will be presented.
All-silica mirrors manufactured using GLancing Angle Deposition (GLAD) are a promising approach for optics with improved LIDT. However, water content may increase over time due to the porosity of the low index silica layers, potentially changing the LIDT. Additionally, consecutive irradiation during LIDT testing may remove stored water and influence the LIDT.
Laser calorimetry, spectrophotometry and LIDT measurements, applying S-on-1 and R-on-1 methods, were used in order to determine the impact of laser-induced removal of stored water on the absorption, spectral behavior and laser damage resistance of all-silica mirrors. Influence of water reabsorption was investigated under different environmental atmospheric conditions.
Optical elements are the main parts in laser system, which limit the total generated output power due to optical resistivity. The increase of beam diameter dimensions may compensate the optical performance of elements, however it leads to the increase of laser system size. Thus, any improvement in optical coatings has impact on either higher output power or lowering the size of system itself. Glancing angle deposition method is presented to produce porous nanostructured coatings, which are characterized by low inner stress. Multilayer Bragg mirrors are formed using only silica material to achieve high laser-induced damage threshold value. Laser conditioning effect is applied, to improve optical performance in ns regime and reach LIDT values over 180 J/cm2.
Optical elements are the main parts in laser system, which limit the total generated output power due to optical resistivity. The increase of beam diameter dimensions may compensate the optical performance of elements, however it leads to the increase of laser system size. Thus, any improvement in optical coatings has impact on either higher output power or lowering the size of system itself. Glancing angle deposition method is presented to produce porous nanostructured coatings, which are characterized by low inner stress. Multilayer Bragg mirrors are formed using only silica material to achieve high laser-induced damage threshold value. Laser conditioning effect is applied, to improve optical performance in ns regime and reach LIDT values over 180 J/cm2.
Optical components are the main parts in laser systems, which limits the total generated output power due to laser-induced damage. At nanosecond laser pulses materials experiences thermal expansion phenomena, therefore optical coatings gain stress leading to breakdown. Moreover, the main resistance to laser radiation is limited by material itself (band gap). Glancing angle deposition method is presented to produce porous nanostructured coatings, which are characterized by low inner stress. Optical resistivity dependance on porosity of several materials such as aluminium, niobium and silicium oxides singlelayers was evaluated. Furthermore, all-silica Bragg mirror is formed and optical properties investigated in different environments to achieve stable and superior optical resistance.
Optical components are the main parts in laser systems, which limit the total generated output power due to laser-induced damage. At nanosecond laser pulses materials experience thermal expansion, therefore optical coatings gain stress leading to breakdown. Moreover, the main resistance to laser radiation is limited by material itself (band gap). Glancing angle deposition method is presented to produce porous nanostructured coatings, which are characterized by low inner stress. Optical resistivity dependance on porosity of several materials such as aluminium and niobium oxides single layers were evaluated. Furthermore, all-silica Bragg mirrors are formed and optical properties investigated in different environments to achieve stable and superior optical resistance.
In this work we present a new all-silica coating - polarizer, which is also capable to withstand high density of radiation. In order to demonstrate the versatility of presented approach, several coating designs have been modelled and two of them fabricated together with the full-scale measurements and analysis necessary for polarizers implementation into high power microlaser systems. Two polarizing coatings at the wavelength of 355 nm have been formed using two stepper motors based GLAD system. Afterwards optical and structural analysis have been performed including spectrophotometric, atomic-force microscopy (AFM), scanning electron microscopy (SEM) and optical resistivity measurements.
Optical components are the main parts in laser systems and also the limiting factor for high power laser. All-silica based optical components proved to have extremely high laser induced damage threshold and were already tested on standard glass substrates. Such coatings are fabricated by employing glancing angle deposition method, combination of nanostructured porous low refractive index and dense high refractive index thin films were fabricated. Anti-reflection coatings and mirrors with required reflection were achieved, which have superior LIDT values (50.7 J/cm2). Antireflection coating was deposited directly on BBO crystal and results are demonstrated. In this work, the possibility to improve microlaser systems with all-silica coatings is presented.
In present work, oblique angle deposition technique was employed to form nano-structured anisotropic layers evaporating amorphous materials. The combination of birefringent nano-structured and isotropic layers allows to form highly transparent (T ~ 99 %) wave-plates. Furthermore, such combination can be used to form two spectrally separated Bragg reflection zones for perpendicular polarizations. This feature allows to form polarizers for zero angle applications. Both elements can be manufactured using only one material by changing only its structural morphology what leads to superior LIDT value. In this work, the possibility to evaporate waveplates and polarizers for zero angle applications was shown.
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