How laser damage resistance of HfO2/SiO2 optical coatings is affected by embedded contamination caused by pausing the deposition process
Abstract not provided.
Publications
Overview of large optics coating capabilities and operations at Sandia National Laboratories
Abstract not provided.
Cleaning protocols for increased laser damage resistance of antireflection coatings
Abstract not provided.
Design and Production of an Optical Coating for High Reflection of Femtosecond Petawatt-Class Laser Pulses at 45deg Incidence P Polarization
Abstract not provided.
Analysis of laser damage tests on a coating for broad bandwidth high reflection of femtosecond pulses
Proceedings of SPIE - The International Society for Optical Engineering
We have designed and produced an optical coating suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of petawatt (PW) class fs laser pulses of ∼ 900 nm center wavelength. We have produced such BBHR coatings consisting of TiO
Design and laser damage properties of a dichroic beam combiner coating for 22.5° incidence and S polarization with high-transmission at 527nm and high-reflection at 1054nm
Proceedings of SPIE - The International Society for Optical Engineering
We have designed a dichroic beam combiner coating consisting of 11 HfO2/SiO2 layer pairs deposited on a large fused silica substrate. The coating provides high transmission (HT) at 527 nm and high reflection (HR) at 1054 nm for light at 22.5° angle of incidence (AOI) in air in S polarization (Spol). The coating's design is based on layers of near half-wave optical thickness in the design space for stable HT at 527 nm, with layer modifications that provide HR at 1054 nm while preserving HT at 527 nm. Its implementation in the 527 nm/1054 nm dual wavelength beam combiner arrangement has two options, with each option requiring one or the other of the high intensity beams to be incident on the dichroic coating from within the substrate (from glass). We show that there are differences between the two options with respect to the laser-induced damage threshold (LIDT) properties of the coating, and analyze the differences in terms of the 527 nm and 1054 nm E-field intensity behaviors for air → coating and glass → coating incidence. Our E-field analysis indicates that LIDTs for air → coating incidence should be higher than for glass → coating incidence. LIDT measurements for Spol at the use AOI with ns pulses at 532 nm and 1064 nm confirm this analysis with the LIDTs for glass → coating incidence being about half those for air → coating incidence at both wavelengths. These LIDT results and the E-field analysis clearly indicate that the best beam combiner option is the one for which the high intensity 527 nm beam is incident on the coating from air and the 1054 nm high intensity beam is incident on the coating from glass.
How reduced vacuum pumping capability in a coating chamber affects the laser damage resistance of HfO2/SiO2 antireflection and high-reflection coatings
Proceedings of SPIE - The International Society for Optical Engineering
Optical coatings with the highest laser damage thresholds rely on clean conditions in the vacuum chamber during the coating deposition process. A low base pressure in the coating chamber, as well as the ability of the vacuum system to maintain the required pressure during deposition, are important aspects of limiting the amount of defects in an optical coating that could induce laser damage. Our large optics coating chamber at Sandia National Laboratories normally relies on three cryo pumps to maintain low pressures for e-beam coating processes. However, on occasion, one or more of the cryo pumps have been out of commission. In light of this circumstance, we decided to explore how deposition under compromised vacuum conditions resulting from the use of only one or two cryo pumps affects the laser-induced damage thresholds of optical coatings. The coatings of this study consist of HfO2 and SiO2 layer materials and include antireflection coatings for 527 nm at normal incidence, and high reflection coatings for 527 nm, 45° angle of incidence (AOI), in P-polarization (P-pol).
Design and development of laser damage resistant low group delay dispersion optical coatings for high reflection at 45o incidence P polarization and wavelengths from 800 to 1000 nm
Sandia journal manuscript; Not yet accepted for publication
This paper describes the modelling and design development of an optical coating that is suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) and fs-class laser pulses whose frequencies correspond to wavelengths from 800 to 1000 nm, and that can eventually be produced uniformly on meter-class optical substrates. The coating design process was guided by specifications of not only high reflection but also high laser-induced damage threshold (LIDT) as well as low group delay dispersion (GDD) for reflected light over the broad, 200 nm bandwidth in order to minimize temporal broadening of the fs pulses upon reflection. The coating is based on TiO2/SiO2layer pairs by means of e-beam evaporation with ion-assisted deposition (IAD). We used OptiLayer Thin Film Software to explore coating designs with a limited optimization process starting from TiO2/SiO2 layer pairs with layer thicknesses in an opposite “chirp” arrangement. This approach proved to be successful, leading to a design with R > 99.5% from 801 – 999 nm and GDD < 20 fs2 from 843 – 949 nm (45° AOI, Ppol). The GDD behaves in a smooth way that lends itself to compensation of GDD effects. Also, the electric field intensities are favorable to high LIDT in that they quench rapidly into the outer coating layers or are of moderate strength, or they are located in the higher band gap SiO2 layers.
Comparative STEREO-LID (Spatioorally REsolved Optical Laser-Induced Damage) studies of critical defect distributions in IBS, ALD, and electron-beam coated dielectric films
Proceedings of SPIE - The International Society for Optical Engineering
The laser damage behavior of high quality coatings under nanosecond pulse illumination is controlled by statistically distributed defects, whose physical nature and defect mechanisms are still largely unknown. Defect densities are often retrieved by modeling the fluence dependence of the damage probability measured by traditional damage test (TDT) methods, based on âdamage' or âño damage' observations. STEREO-LID (Spatioorally REsolved Optical LaserInduced Damage) allows the determination of the damage fluence (and intensity) in a single test by identifying the initiation of damage both temporally and spatially. The advantages of this test method over the TDT are discussed. In particular, its ability to retrieve detailed defect distribution functions is demonstrated by comparison of results from HfO2 films prepared by ion-assisted electron beam evaporation, ion-beam sputtering, and atomic layer deposition.
Impact of different cleaning processes on the laser damage threshold of antireflection coatings for Z-Backlighter optics at Sandia National Laboratories
Optical Engineering
We have examined how different cleaning processes affect the laser-induced damage threshold of antireflection coatings for large dimension, Z-Backlighter laser optics at Sandia National Laboratories. Laser damage thresholds were measured after the coatings were created, and again 4 months later to determine which cleaning processes were most effective. There is a nearly twofold increase in laser-induced damage threshold between the antireflection coatings that were cleaned and those that were not cleaned. Aging of the coatings after 4 months resulted in even higher laser-induced damage thresholds. Also, the laser-induced damage threshold results revealed that every antireflection coating had a high defect density, despite the cleaning process used, which indicates that improvements to either the cleaning or deposition processes should provide even higher laser-induced damage thresholds.
Design and Development of Laser Damage Resistant Low Group Delay Dispersion Optical Coatings for High Reflection at 45deg Inciidence P Polarization and Wavelengths from 800 to 1000 nm
Abstract not provided.
Repair of a Mirror Coating on a Large Optic for High Laser Damage Applications using Ion Milling and Over-Coating Methods
Abstract not provided.
Broad Bandwidth Coating Development: Coating Design Report
Abstract not provided.
Demonstration of Electrothermal Instability Mitigation by Using Thick Dielectric Coatings on Magnetically Imploded Conductors
Physical Review Letters
Abstract not provided.
Reactive ion-assisted deposition of e-beam evaporated titanium for high refractive index TiO2layers and laser damage resistant, broad bandwidth, high-reflection coatings
Applied Optics
High-reflection coatings with broad bandwidth can be achieved by pairing a low refractive index material, such as SiO2, with a high refractive index material, such as TiO2. To achieve high refractive index, low absorption TiO2films, we optimized the reactive, ion-assisted deposition process (O2levels, deposition rate, and ion beam settings) using e-beam evaporated Ti. TiO2high-index layers were then paired with SiO2low-index layers in a quarter-wave-type coating to achieve a broader high-reflection bandwidth compared to the same coating composed of HfO2/SiO2layer pairs. However, the improved bandwidth exhibited by the TiO2/SiO2coating is associated with lower laser damage threshold. To improve the laser damage resistance of the TiO2/SiO2coating, we also created four coatings where HfO2replaced some of the outer TiO2layers. We present the laser damage results of these coatings to understand the trade-offs between good laser damage resistance and high-reflection bandwidth using TiO2and HfO2.
Repair of a mirror coating on a large optic for high laser damage applications using ion milling and over-coating methods
Proceedings of SPIE - The International Society for Optical Engineering
When an optical coating is damaged, deposited incorrectly, or is otherwise unsuitable, the conventional method to restore the optic often entails repolishing the optic surface, which can incur a large cost and long lead time. We propose three alternative options to repolishing, including (i) burying the unsuitable coating under another optical coating, (ii) using ion milling to etch the unsuitable coating completely from the optic surface, and then recoating the optic, and (iii) using ion milling to etch through a number of unsuitable layers, leaving the rest of the coating intact, and then recoating the layers that were etched. Repairs were made on test optics with dielectric mirror coatings according to the above three options. The mirror coatings to be repaired were quarter wave stacks of HfO2 and SiO2 layers for high reflection at 1054 nm at 45° incidence in P-polarization. One of the coating layers was purposely deposited incorrectly as Hf metal instead of HfO2 to evaluate the ability of each repair method to restore the coating's high laser-induced damage threshold (LIDT) of 64 J/cm2. The repaired coating with the highest resistance to laser-induced damage was achieved using repair method (ii) with an LIDT of 49-61 J/cm2.
Reactive Ion-Assisted Deposition of E-Beam Evaporated Ti for High Refractive Index TiO2 Layers and High Reflection Coatings Exhibiting Increased Bandwidth and Laser Damage Resistance
Abstract not provided.
2013 OIC Measurement Problem Contest Entry by Sandia National Laboratories
Abstract not provided.
Reactive, Ion-Assisted Deposition of E-Beam Evaporated Ti for High Refractive Index TiO2 Layers and Laser Damage Resistant, Broad Bandwidth, High Reflection Coatings
Applied Optics
Abstract not provided.
Reactive, Ion-Assisted Deposition of E-Beam Evaporated Ti for High Refractive Index TiO2 Layers and Laser Damage Resistant, Broad Bandwidth, High Reflection Coatings
Applied Optics
Abstract not provided.
Results 51–70 of 70