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We report on a novel starting design structure of highly-dispersive mirror (HDM) which combines quarter-wavelength structure and multi-cavities, introducing more wavelength-dependent storage times of incident radiation and group delay (GD). Based on such structure, a HDM with new advanced group delay dispersion (GDD) of −20 000 fs2 in the wavelength range of 1035–1045 nm is designed, fabricated and characterized. Our proposed initial multilayer structure is instructive in designing HDM aiming at introducing large GDD. Our HDM further pushes the maximum negative GDD allowed by the design’s total physical thickness to its limitation. It offers an ideal trade-off between GDD and total mirror thickness. The HDM has been applied in a fiber-chirped system, providing a considerable compensation of GDD reaching −200 000 fs2 with only 10 reflections between two mirrors, and laser pulse compression from 2.8 ps to 213 fs is realized.

A low-dispersion mirror (LDM), an important component in ultrafast laser systems, requires both a broad low-dispersion laser-induced damage threshold (LIDT). It is difficult for a traditional quarter-wavelength-based dielectric LDM to achieve these characteristics at the same time. We propose a novel, to the best of our knowledge, low-dispersion mirror (NLDM) that combines periodic chirped layers at the top and alternating quarter-wavelength layers at the bottom. Low dispersion is achieved by introducing a large same group delay (GD) for different wavelengths, so the bandwidth is broadened greatly. In addition, owing to the staggered electric field intensity peak effect in the structure, the NLDM shows the potential for high laser damage resistance. The experiments demonstrated that the NLDM doubles the low-dispersion bandwidth, while the LIDT is also increased compared with the LDM. This novel concept results in improved performance and paves the way toward a new generation of the LDM for ultrafast bandwidth and a high laser applications.

Metal-dielectric low dispersion mirrors (MLDM) have a promising application prospect in petawatt (PW) laser systems. We studied the damage characteristics of MLDM and found that the damage source of MLDM (Ag + Al2O3+SiO2) is located at the metal-dielectric interface. We present the effect of the interface on the femtosecond laser damage of MLDM. Finite element analysis shows that thermal stress is distributed at the interface, causing stress damage which is consistent with the damage morphology. After enhancing the interface adhesion and reducing the residual stress, the damage source transfers from the interface to a surface SiO2 layer, and the damage threshold can be increased from 0.60 J/cm2 to 0.73 J/cm2. This work contributes to the search for new techniques to improve the damage threshold of MLDM used in PW laser systems.

The dispersion oscillation and damage threshold of a dispersive mirror (DM) are the key influencing factors for high-quality pulses and outputting high power density. Here, we studied the femtosecond damage behavior of low-oscillation DMs(LODM) with SiO2 sculptured layer. The monochromatic standing wave field(SWF) distribution widely used in ultrafast laser damage analysis is sufficient in Bragg mirror. In more complex systems, the actual electric field intensity(typically smaller) will dynamically change due to the broad bandwidth and the time difference of pulse propagation. Time-domain dynamic electric field intensity displays that the spatio-temporal evolution of the pulse within the stacks averages the electric field intensity, especially the electric field in the deeper layers. The dynamic effect of few-cycle pulses or attosecond pulses damage will be more meaningful. The time-domain dynamic electric field model can elucidate the ultrafast laser damage behavior. Introducing the time-domain dynamic electric model into the merit function can help us design optical coatings with high damage thresholds.

As important part of components for 193 nm lithography, AlF3 coatings deposited by resistive heating method acquire advantages like lower optical loss and higher laser damage threshold, but they also possess some disadvantages like worse stability, which is what aging effect focuses on. AlF3 single-layer coatings were deposited; optical property, surface morphology and roughness, and composition were characterized in different periods. Owing to aging effect, refractive index and extinction coefficient increased; larger and larger roughness caused more and more scattering loss, which was in the same order with absorption at 193.4 nm and part of optical loss; from composition analysis, proportional substitution of AlF3 by alumina may account for changes in refractive index as well as absorption.

Low dispersive with broad bandwidth mirrors serve as indispensable elements in ultrafast laser systems. We report on three coatings, quarter-wave high reflection mirror, metal-dielectric mirror and ternary composite mirror, which are suitable for broad bandwidth high reflection (BBHR) with 800nm center wavelength. Mirrors based on quarterwave Ta2O5/SiO2 layers are designed and fabricated. By depositing the quarter-wave HfO2/SiO2 layers on the metallic material, we have achieved the mirror with lager low-dispersive bandwidth, this design takes advantage of broad high reflection bandwidth of metal and high laser induced damage threshold (LIDT) of HfO2. Moreover, we have deposited HfO2/SiO2 layers on Ta2O5/SiO2 layers, since HfO2 demonstrates higher damage threshold than Ta2O5, such combination reach an ideal trade-off between the low-dispersive bandwidth and high LIDT comparing with traditional quarter-wave Ta2O5/SiO2 layers. Our BBHR mirrors are produced by means of dual-ion-beam sputtering technique. The designs afford low group delay dispersion (GDD) for reflected light over the broad bandwidth in order to minimize temporal broadening of the fs pulses. The design’s GDD behaves in a smooth way, and its electric field intensities show promise for high LIDTs. Reflectivity and GDD measurements indicate good performance of the BBHR design. LIDTs of the produced BBHR mirrors are also tested and compared.

We propose an initial multilayer structure to design high dispersive mirror (HDM) and aim at introducing large group delay dispersion (GDD). In film deposition, based on the uniformity, a HDM pair reduce the GDD oscillation effectively.

A broadband antireflection film was prepared with SiO2 by glancing angle deposition. The refractive index of the SiO2 film was tuned from 1.15 to 1.45 by adjusting the deposition angle. A novel broadband antireflection film was designed with the graded index film. The average reflectivity of antireflection film is less than 0.41% between 400 nm and 1800 nm wavelength range at 0° incident angle.

A broadband, polarization-independent, and wide angle metamaterial absorber (MA) with tapered cylinder structures is investigated with finite difference time domain simulations. The titanium nitride (TiN) and indium tin oxide (ITO) thin film are introduced as the tapered cylinder structures. The unit cell structure is mainly composed of two pairs of TiN/ITO layers and one TiN base layer. The absorption is higher than 99% between the wavelength 700 nm and 1000 nm. The broadband, polarization independent average absorption remains above 95% between 400 nm and 1200 nm with a wide range of incident angles from 0° to 40°. The electrical field intensity distributions are studied to disclose the broadband absorption mechanism. This designed broadband absorber appears to be very promising applications in the plasmonic sensing and photovoltaic devices.

Complementary analysis techniques are applied in this work to study the interface structure of Mo/Si multilayers. The samples are characterized by grazing incident x-ray reflectivity, x-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and extreme ultraviolet reflectivity. The results indicate that the layer thickness is controlled well with small diffusion on the interface by forming MoSi2. Considering MoSi2 as the interface composition, simulating the result of our four-layer model fits well with the measured reflectivity curve at 13.5 nm.

Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation. Spectral measurement results showed that as the deposition temperature increased from 100°C to 300°C, the transmittance of the films in the wavelength range from 350 nm to 2100 nm decreased. After annealing in air at 500°C, the transmittance significantly increased and approached that of uncoated fused quartz. Based on the Tauc plot method and Mott–Davis–Paracrystalline model, the optical band gap of Ge films was calculated and interpreted. The difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing, while having little effect on the optical band gap after annealing. Furthermore, due to oxidation of Ge films, the optical band gap was significantly increased to ∼5.7 eV after annealing.

Space laser systems are widely used in communication, altimeter and Doppler radar. UV laser, which possesses high spectral resolution and provides with the detection of the parallel polarized molecular (Rayleigh) and particle (Mie) backscattered signals has promising use in atmosphere detection and Doppler radar. No orbiting satellite carrying with 355nm laser has yet been launched owing to the laser induced damage of coatings. Coatings for spaceborne laser system are widely used in spacecraft with laser system to improve the transmittance of the optical system and to adjust the laser beams. An effective way to improve the lifetime of the coatings and the resistance to the environment is to increase laser induced damage threshold (LIDT). The subsurface damage (SSD) of the substrate is one of the major harmful factors in laser induced damage. In our study, 355nm high-reflection (HR) and anti-reflective (AR) coatings deposited by dual-ion beam sputtering (DIBS) were stable and showed lit

The plasma scald damage is the most typical laser damage morphology presented on the laser conditioned HfO 2 /SiO 2 mirrors. In order to provide guidance for defining the acceptance quantitative specification for the plasma scald on these laser conditioned mirrors, the simulations about the downstream beam modulations of the plasma scald are investigated based on its damage characteristics and the diffraction theory. The single plasma scald with the typical size, induced by the laser conditioning, can hardly cause damage to the downstream optics and its influence on the beam contrast can be reduced easily with the increment of the propagation distance. Those with small size and large depth, or those with big size and shallow depth can also hardly induce downstream damage, but the beam contrasts become worse with the increment of the size of the concave part as well as its depth. For a maximum plasma scald observed on the laser conditioned mirror, the intensity modulation peak is close to 1.3 and the beam contrast reaches to 25% even at 2 m downstream from the mirror. For multi plasma scalds, more diffraction rings show up in the downstream beam and further decrease the overall uniformity of the beam. The uniformity of the beam gets worse as the number of the plasma scald is increased. When the density of the plasma scald with the typical size in these 1ωHfO 2 /SiO 2 mirrors reaches 20 per 1 cm 2 , the beam contrast is less than 6%.

A broadband metamaterial absorber (MA) based on the titanium nitride (TiN) nano-disk array is studied using finite difference time domain simulations. The semiconducting indium tin oxide (ITO) thin film is introduced as the space layer in this sandwiched structure. Utilizing the symmetrical geometry of the MA structure, polarization insensitivity of the broadband absorption was gained. The absorber with TiN nano-disk array shows a peak absorbance of 99 % and larger than 98 % from 560 to 675 nm by numerical simulation. This compact design may have potential applications in the plasmonic sensing and photovoltaic devices.

The combination of deep wet etching and a magneto-rheological finishing (MRF) process is investigated to simultaneously improve laser damage resistance of a fused-silica surface at 355 nm. The subsequently deposited SiO2 coatings are researched to clarify the impact of substrate finishing technology on the coatings. It is revealed that a deep removal proceeding from the single side or double side had a significant impact on the laser-induced damage threshold (LIDT) of the fused silica, especially for the rear surface. After the deep etching, the MRF process that followed does not actually increase the LIDT, but it does ameliorate the surface qualities without additional LIDT degradation. The combination guarantee both the integrity of the surface’s finish and the laser damage resistance of the fused silica and subsequent SiO2 coatings.

Nanosecond single- and multiple-pulse laser damage studies on HfO2/SiO2 high-reflection (HR) coatings are performed at 532 nm. For single-pulse irradiation, the damage is attributed to the defects and the electric intensity distribution in the multilayer thin films. When the defect density in the irradiated area is high, delamination is observed. Other than the 1064 nm laser damage, the plasma scalding of the 532 nm laser damage is not pits-centered for normal incidence, and the size of the plasma scalding has no relation to the defect density and position, but increases with the laser fluence. For multiple-pulse irradiations, some damage sites show deeper precursors than those from the single-shot irradiation due to the accumulation effects. The cumulative laser-induced damages behave as pits without the presence of plasma scalding, which is unaffected by the laser fluence and shot numbers. The damage morphologies and depth information both confirm the fatigue effect of a HfO2/SiO2 HR coating under 532 nm laser irradiation.

We prepare SiO2 coatings on different substrates by either electron-beam evaporation or dual ion-beam sputtering. The relative transmittances of the SiO2 coatings are measured during the heating process. The SiO2 coating microstructures are studied. Results indicate that the intensity and peak position of moisture absorption are closely related to the microstructures of the coatings. The formation of microstructures depends not only on the preparation process of the coatings but also on the substrate characteristics.

We present the design and fabrication approach of a rugate narrow band minus filter. A method for the fabrication of graded-index coatings by rapidly alternating deposition of low (SiO2) and high (Al2O3) refractive index materials is introduced, and this technology was used to fabricate a rugate structure. This paper mainly discusses about rugate narrow band minus filter design and fabrication approach. The experimental results show the measured transmittance spectra are in good agreement with the designed value. The laser-induced damage threshold (LIDT) of the narrow band rugate minus filter is measured.

We describe the design, fabrication and performance of an optimized one-dimensional subwavelength grating for use in 1064 nm wavelength laser systems. The laser-induced damage threshold (LIDT) under the irradiation of 12 ns 1064 nm pulses on the grating was performed, and a higher LIDT was obtained compared with LIDT of traditional antireflective coatings. Laser irradiation produces some morphological modifications on grating. Light interferometric surface profiler, scanning electron microscope and atomic force microscope were used to study these modifications, and these studies indicate the significant ablation and resolidification have occurred. To understand possible damage mechanisms, the role of electric field distribution inside the grating during the laser radiation process was investigated by a three-dimensional finite difference time-domain method, and the simulation result indicates the temperature distribution resulting from the internal electric field may be the main factor behind the damage.

Wave propagation of symmetry incidence on the biaxial birefringent film is discussed in this paper based on the characteristic matrix method. Furthermore, based on the refractive index surface, the refractive indices and effective optical admittances of the forward and backward propagating extraordinary waves (p-polarized wave) are analyzed in detail. With regard to the symmetry incidence, optical properties, such as the input optical admittance, transmittance and reflectance, are not identical for an extraordinary wave under common condition, i.e., angular selectivity. Based on an analysis of refractive index surface, the effective optical admittances of the forward and backward propagating extraordinary waves are equal in this particular case; transmittance and reflectance under the symmetry incidence are completely overlapped, similar to findings in the isotropic thin film. We validate our analysis using the developed software package. Based on the novel theory analysis, we can gain a new perspective of symmetry incidence about angular selectivity for the biaxial birefringent film.

Commercial fused silica (50 mm diameter × 5 mm thickness) irradiated by single pulse of Nd:YAG laser (1064 nm, 12 ns) is experimentally investigated. The exit surface of fused silica is easier to be damaged than the entrance surface, so in this paper we only study the damage formed on the exit surface. The typical damage morphologies, irradiated at normal and oblique incidence, were observed with scanning electron microscope and atomic force microscope. The concentric ring structures with a central defect precursor are appeared in all damage sites. Furthermore, the whole damage sites are filled with the surface periodic striped structures, which direction is perpendicular to the incident electric field. Further analysis show that the incident energy has great effect on the size of damage sites, the depth of damage sites, and also the depth of the ripples, but has no effect on the period of the ripples. Additional experiments are performed to investigate the dependency between the period of ripples and the incident angle.

Four mirror coatings were designed for transporting 1064 nm light, and prepared under the same process parameters. The laser induced damage threshold (LIDT), electric field distribution, as well as the damage morphology of the prepared transport mirror coating was investigated. The results indicate that the SiO2 overcoat layer and electric field distribution have a great impact on the LIDT and damage morphology of the transport mirror coating. A thicker SiO2 overcoat layer can suppress the delamination damage morphology, and significantly increase the LIDT. For the designs with similar SiO2 overcoat layer thickness, the nano-absorbing defects can survive at higher laser fluence in the design with lower electric field intensity. In addition, the HfO2 over SiO2 interface has a better interfacial strength and less “invisible” nano-absorbing defects than the SiO2 over HfO2 interface, suggesting that improving the SiO2 over HfO2 interfacial quality will be an effective way to enhance the laser damage performance of the transport mirror coating.

As important components in deep-ultraviolet (DUV) optics, especially 193 nm lithographic systems, high-reflectivity (HR) mirrors with excellent optical properties and long lifetimes are needed urgently. In this study, we designed and produced three HR coatings for 193 nm on fused quartz substrates: Al2O3/AlF3 coating, LaF3/AlF3 coating and a double stack mirror with combined Al2O3/AlF3 and LaF3/AlF3. The reflectance of the Al2O3/AlF3 coating with 14 layer pairs reached 98.0% at 193 nm. However, the absorption of Al2O3 prevented the reflectance to increase further. The maximum reflectance of the LaF3/AlF3 coating with 15 layer pairs reached 98.1%, with initial micro-cracks formation. The reflectance decreased as the number of layer pairs increased to 16 because of numerous micro-cracks. The mirror with combined Al2O3/AlF3 and LaF3/AlF3 coatings which combined their advantages obtained a reflectance of 98.8% at 193 nm after deposition. This value could still reach 98.5% at 4 months after deposition and remain stable thereafter. Therefore, the combined coating of Al2O3/AlF3 and LaF3/AlF3 is an excellent candidate for practical application.

A model is developed to improve thickness uniformity of coatings on spherical substrates rapidly and automatically using fixed shadow masks in a planetary rotation system. The coating thickness is accurately represented by a function composed of basic thickness, self-shadow effect, and shadow mask function. A type of mask with parabolic contours is proposed, and the thickness uniformity of coatings on spherical substrates can be improved in a large range of ratios of clear aperture (CA) to radius of curvature (RoC) by optimizing shadow masks using a numerical optimization algorithm. Theoretically, the thickness uniformity improves to more than 97.5% of CA/RoC from -1.9 to 1.9. Experimentally, the thickness uniformities of coatings on a convex spherical substrate (CA/RoC = 1.53) and on a concave spherical substrate (CA/RoC=-1.65) improve to be better than 98.5% after corrected by the shadow masks.

Coating stacks of HfO 2 /SiO 2 and Ta 2 O 5 /SiO 2 were separately prepared by electron beam evaporation and dual ion beam sputtering. Damage characteristics at the interlayer interfaces were analyzed after irradiation of the coatings by a 1064 nm laser. The cross-sectional morphologies of damage spots indicated that peeling-off damages always occurred at the interface where the low refractive index material (SiO 2 ) was deposited on the high refractive index material (HfO 2 or Ta 2 O 5 ). The effects of interface microstructure and components on peeling-off damages were also discussed. The microstructure of the interface was not a major factor that influenced peeling-off damages. Incomplete oxides (SiO x ) and Na, K, Li ions accumulated near the interface and caused the formation of micro-defects layers with nano-sized thicknesses. Micro-defects layers maybe reduced adhesion of different interfaces and formed plasmas by absorbing laser energy. Finally stripping damages happened from micro-defects layers during irradiation by a 1064 nm laser.

Antireflective sub-wavelength structures with high laser-induced damage threshold on fused silica are fabricated using a self-assembly technique, in which a porous yttrium oxide film is deposited as a mask followed by alkaline etching. By controlling the etching time, several sub-wavelength structures with different height, density and diameter have been made. The best reflectance is less than 2.87% for wavelengths from 300 to 1000 nm after 1.5 h etching. The laser-induced damage threshold of the etched glass measured by a 10 ns Nd:YAG laser at a wavelength of 532 nm was as high as 30 J/cm2 compared to 16 J/cm2 of blank glass. The specular reflectance of structures matches the theoretical simulation using a thin-film multilayer model, and the results reveal that the shape of the structures is similar to the calculated parabolic shape. Achieving antireflective sub-wavelength structures on fused silica paves the way for applications in laser systems.

We present a monitoring strategy based on using two pieces of witness glass, which are brought to the measuring position in a specially chosen sequence, each witness glass is monitored by one single wavelength. To reduce the thickness error, some thick layers are divided into two layers and monitored by different witness glasses. Theoretical analysis and experimental results have demonstrated that the proposed monitoring strategy can achieve spectral performance close to the theoretical design.

Multiple laser irradiations induce a critical issue as regards the lifetime of optical components. HfO 2 /SiO 2 AR coatings for 1064 nm were prepared by conventional electron beam deposition. The evolution of laser-induced damage threshold (LIDT) and 100% damage probability threshold with shot numbers were investigated to illustrate the incubation mechanism of defect-induced damages and the intrinsic material modifications of coatings. It was found that the multi-shot LIDTs were lower than that of single-shot because of “fatigue effect”. The 100% damage probability threshold also decreased with increasing shot numbers. This incubation phenomenon implied laser-induced modifications to the coating material that weaken it to subsequent pulse exposures. LID probability curves simulated with a statistical model assuming Gaussian distribution of defect threshold were used to highlight information on defects. Simulation results showed that the thresholds of different kinds of defects decreased with the increase of shot numbers. Optical microscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and step profiler were employed in mapping damage morphology features and damage depth to discuss the initiators and mechanism of damage initiation. Additionally, damage regions were accessed by X-ray photoelectron spectroscopy (XPS) to indicate the changes in elemental content and valence of the materials with increasing pulse numbers.

Metal multi-layer dielectric gratings (MMDG) for pulse compressors in high-energy laser systems should provide broad bandwidth as well as high laser-induced damage thresholds. The non-uniform optical near-field distribution of MMDG is an important factor that limits damage resistant capabilities. MMDG for pulse compressors operating at 800 nm with a corrugated SiO2 layer are designed by using a genetic algorithm and the Fourier mode method. The diffraction efficiency, bandwidth, and near-field distribution of the MMDG are theoretically investigated. For the single dielectric match layer grating, the bandwidth is 140 nm, if the thickness and refractive index of the match layer are changed, the maximum electric field in the grating ridge, match layer, and metal layer of the grating increases with the decrease in grating diffraction efficiency. For the multi-dielectric match layer grating, the bandwidth and the maximum electric field in the metal layer decrease with the increase in high- and low-index material pairs, and the maximum electric field in the grating ridge and match layer initially decreases and then increases. Over a wide wavelength range, the maximum electric field in the grating ridge, match layer, and metal layer is minimal near the central wavelength. Moreover, MMDG should be used at larger incident angles while keeping enough bandwidth to reduce the electric field in the grating.

In the pursuit for 355 nm high laser resistant dielectric coatings, layer-pair number of 10 and 15 LaF3/AlF3 high reflectors with and without SiO2 undercoat were prepared on BK7 substrates. The results indicate considerable increase in 355 nm laser-induced damage threshold (LIDT) for samples with undercoat. The samples were analyzed in Normalized Electric Field Intensity distribution, total stress, damage depth and damage morphology, revealing that SiO2 undercoat benefits fluoride coatings by shielding substrate defects and reducing coating defects.

Laser resistance and stress-free mirrors, windows, polarizers, and beam splitters up to $400~\mathrm{mm} \times 400~\mathrm{mm} $ are required for the construction of the series SG facilities. In order to improve the coating quality, a program has been in place for the last ten years. For the small-aperture pick-off mirror, the laser-induced damage threshold (LIDT) is above $60~\mathrm{J} / {\mathrm{cm} }^{2} $ (1064 nm, 3 ns), and the reflected wavefront is less than $\lambda / 4~(\lambda = 633~\mathrm{nm} )$. The Brewster-angle polarizing beam splitter ($\Phi 50\times 10~\mathrm{mm} $) shows the best LIDT result, up to $29. 8~\mathrm{J} ~{\mathrm{cm} }^{- 2} $ (1064 nm, 10 ns) for a p-polarized wave in the 2012 damage competition of the XLIV Annual Boulder Damage Symposium. For the larger-aperture mirror and polarizer, the LIDT is above $23~\mathrm{J} ~{\mathrm{cm} }^{- 2} $ (1064 nm, 3 ns) and $14~\mathrm{J} ~{\mathrm{cm} }^{- 2} $ (1064 nm, 3 ns), respectively. The reflected wavefront is less than $\lambda / 3~(\lambda = 633~\mathrm{nm} )$ at the used angle.

Porous antireflective (AR) coatings were prepared by the neutral solution leaching of borosilicate glass. The textured surfaces typically exhibit broadband and wide-angle AR behavior with an extremely low scattering over 300–1400 nm spectral range. The coating thickness increases with increase in the solution concentration, temperature and etching time, leading to the tunable transmittance spectra in the entire wavelength range. And the thickness and corresponding refractive index of AR coatings can be calculated using transmittance simulation. The relationship of experimental variations, coating thickness and etching rate was obtained and discussed. These porous AR coatings with controlled thickness and refractive index would have broad potential applications.

In this study a new design concept of the Fabry-Perot filter, constructed with an anisotropic space layer and a couple of isotropic mirrors, was proposed based on the Maxwell equations and the characteristic matrix method. The single- and double-cavity Fabry-Perot filters were designed, and their optical properties were investigated with a developed software package. In addition, the dependence of the transmittance and phase shift for two orthogonal polarization states on the column angle of the anisotropic space layer and the incidence angle were discussed. We demonstrated that the polarization state of electromagnetic waves and phase shifts can be modulated by exploiting an anisotropic space layer in a polarization F-P filter. Birefringence of the anisotropic space layer provided a sophisticated phase modulation with varied incidence angles over a broad range, resulting in a wide-angle phase shift. This new concept would be useful for designing optical components with isotropic and anisotropic materials.

As an important component in 193nm laser system, high-reflectance (HR) coatings with excellent optical and mechanical properties are needed urgently. In this study, we designed and produced three different HR coatings at 193nm, Al2O3/ AlF3 coating, LaF3/ AlF3 coating and a double stack mirror with combination of Al2O3/ AlF3 and LaF3/ AlF3. With 14 layer pairs, the reflectance of Al2O3/ AlF3 coating could reach 98% which could not get higher duo to the absorption of Al2O3. The reflectance of LaF3/ AlF3 coatings could achieve 98.13% with 15 layer pairs. When the layer pair increased to 16, the reflectance lessened ascribed to steep rise in scattering loss caused by micro-cracks occurred in the coatings. A mirror with combination of Al2O3/ AlF3 and LaF3/ AlF3 could obtain the reflectance of 98.78% as deposited. Even 4 months later the value could still reach 98.47% which was an excellent candidate for practical application.

Thin-film polarizers are essential components of large laser systems, switching the beam out of the primary laser cavity and/or protecting the system from back-reflected light. The requirements for a polarizer include specific spectral performance, high laser-induced damage resistance and low surface figure deformation. Generally speaking, a polarizer coating has a thicker thickness than a mirror coating, and a narrower bandwidth that fulfills the specific spectral specification, which makes the design and fabrication of polarizer coating challenging. Large aperture (up to ~900 mm in diameter) polarizer coating deposited on both BK7 and fused silica substrates with p -polarized transmittance higher than 98%, s-polarized reflectance higher than 99% at 1053 nm, and can tolerance a fluence higher than 17 J/cm 2 (9 ns) at 1053 nm has been achieved.

Thin film beam splitters with high reflectivity at 532 nm and high transmittance at 1064 nm were deposited via reactive electron-beam evaporation with optimized parameters. The damage performance of the samples was investigated under irradiations of 532 nm laser only, 1064 nm laser only, and various combined laser fluences. The damages induced by the 1064 nm laser were primarily attributed to the initiators at the interface between the coatings and substrate. Under 532 nm laser irradiation only, two distinctive damage pits initiated by the submicron absorptive defects located at different coating depths and correlated to interfaces were observed. The damage effect under simultaneous irradiation in multilayer films was also investigated. The respective sensitive defects of the two lasers remained the precursors for causing damage. However, the dominant damage factors in simultaneous irradiation changed with the 1064 nm laser fluence, which also determined the coupling effect between the two lasers in terms of causing damage. Finally, correlative analysis methods were used to discuss the different coupling effects.

In contrast to uncoated substrate, a nonlinear relationship of phase shift with the thicknesses of the thin film makes the calculation of wavefront aberration complicated. A program is compiled to calculate the wavefront aberration of multilayer thin film produced by thickness nonuniformity. The physical thickness and the optical phase change on reflection are considered. As an example, the wavefront aberration of the all-dielectric mirror is presented in ArF excimer lithography system with a typical thickness distribution. In addition, the wavefront errors of the thin film at wavelengths of 193 and 633 nm are compared in the one-piece and two-piece arrangements. Results show that the phase shift upon reflection of the thin film produced by thickness nonuniformity is very sensitive to the incident angle, wavelength, and polarization.

Dispersive mirrors in the wavelength range of 960–1110 nm, 700–900 nm, 950–1150 nm, 600–900 nm, 900–1200 nm, 600–1000 nm and 550–1050 nm are designed, respectively. From the design results, we analyse the choice of material and the approach to dispersion compensation. Furthermore, along with the increase of bandwidth, interaction between group delay dispersion (GDD) oscillation and high reflectivity, and influence of bandwidth on both GDD ripple and reflectivity are discussed.

Polarizers respectively with broad polarizing region bandwidth, large layer thickness error tolerance and high extinction ratio are designed and prepared. Transmittance spectra of the prepared samples are measured at Brewster's angle, and the results show that different requirements can be fulfilled by optimized designs. Spectral performance of designs with higher layer thickness error tolerance coincides better with the theoretical spectra. Laser induced damage threshold of the prepared samples are evaluated. Electric field distribution, defect, film absorption, and damage morphology are investigated, and the results indicate that electric field distribution in high index layers is the main reason that causes the difference of laser induced damage threshold. For both p polarized and s polarized light, the lower the electric field peak value and the farther the layer, which has the strongest electric field away from air, the higher the laser induced damage threshold.

A combined-method based on local optimization and needle optimization is proposed to design broadband dispersion mirrors. The broadband dispersion mirrors are designed by using needle optimization combined with cross application of local optimization and changing high refractive index materials. We combine high efficiency of the local optimization and accuracy of needle optimization. This method can efficiently prevent optimizing process from being captured in a local minimum and obtain higher reflectivity and more smooth group delay dispersion (GDD) curves. The designed dispersion mirrors have a few numbers of layers, which do not have the thin layers that are not easily deposited.

Conventional HfO2/SiO2 and Al2O3/HfO2/SiO2 double stack high reflective (HR) coatings at 532 nm are deposited by electron beam evaporation onto BK7 substrates. The laser-induced damage threshold (LIDT) of two kinds of HR coatings is tested, showing that the laser damage resistance of the double stack HR coatings (16 J/cm2) is better than that of the conventional HR coatings (12.8 J/cm2). Besides, the optical properties, surface conditions, and damage morphologies of each group samples are characterized. The results show that laser damage resistance of conventional HR coatings is determined by absorptive defect, while nodular defect is responsible for the LIDT of double stack HR coatings.

Soft X-ray multilayer reflectors must be deposited on super-smooth surface such as super-polished silicon wafers or glasses, which are complicate, time-consuming and expensive to produce. To overcome this shortage, C films deposited by RF magnetron sputtering were considered to smooth the K9 glass substrates’ surface in the present paper. The structure of C films was systematically studied by XRD and Raman spectrum. The surface morphology and rms-roughness were obtained by AFM. Then, we calculated the impact of the C layers on the reflectivity curve of Mo/Si soft X-ray multilayer reflector around 13.5 nm. The C films exhibit typical amorphous state. With the increasing of power and thickness, the content of sp3 hybrid bonding decreases while the amount or size of well-organized graphite clusters increases. The surface rms-roughness decreases from 2.4 nm to 0.62 nm after smoothed by an 80 nm thick C layer deposited in 500 W, which is the smoothest C layer surface we have obtained. The calculation results show that the theoretical normal incidence reflectivity of Mo/Si multilayer at 13.5 nm increases from 7% to 63%.

Traditional periodic multilayer reflector working in the soft X-ray region should be placed at the designed incidence angle and wavelength, which is extremely difficult and complicate in practice especially for “near water window region” (4.43–6.50 nm). In this region, Ni-like-Ta laser working at the wavelength 4.48 nm provides a possible source which has caught a lot attention. In this paper, to overcome the shortcoming of the periodic structure, top-flat broad band (normal incidence) and broad angular (around quasi-Brewster angle) Cr/C non-periodic multilayer reflector have been designed for the 4.48 nm soft X-ray optical system. In the wavelength region 4.473–4.488 nm, 4.455–4.496 nm and 4.435–4.529 nm, mean theoretical normal-incidence reflectivity can get 35.0%, 24.2% and 12.6%, respectively, by the top-flat broad band reflectors. In the grazing incidence angle region 44.85–45.16°, 44.54–45.46° and 44.02–45.98°, mean s -component theoretical reflectivity at 4.48 nm can get 39.7%, 23.1% and 13.0%, respectively, by the top-flat broad angular reflectors.

Antireflection coatings (AR), beam splitter coatings (BS) and high-reflectance coatings (HR) were prepared to study the effect of material properties and stack structures on the laser induced damage behaviors of coatings at a wavelength of 248 nm. All the coatings were deposited on fused silica substrates by electron beam reactive evaporation technique with the materials of aluminum oxide and silicon dioxide. Laser-induced damage thresholds (LIDTs), damage morphologies and profiles of damage sites of multilayer coatings were characterized to investigate the damage mechanism of coatings irradiated by the excimer laser. Besides, the temperature fields were calculated to better understand the damage mechanism with our programmed software. The results indicate that the absorption of defects and the electric field distribution of thin film greatly contribute to LIDTs of thin films.

Basing on some growth models of thin film, we have investigated the growth mechanism of glancing angle deposition (GLAD) film. The simulation verifies that the overhangs/vacancies also contribute to the columnar growth as well as the self-shadowing effect for GLAD thin film. Besides, we have studied the effect of the deposition rate, surface and bulk diffusions on the microstructure of thin film using the time-dependent Monte Carlo method. The results show that the surface and bulk diffusions can significantly enhance the packing density of thin film in GLAD growth, and the increase of the deposition rate induce the moderate decrease of the packing density. (c) 2006 Elsevier B.V. All rights reserved.

Metal multilayer dielectric gratings (MMDGs) for pulse compressors used in high-energy laser systems should enable high efficiency, as well as provide broad bandwidths and high laser-induced damage thresholds. The effects of duty cycle and the ridge slope angle on the MMDG bandwidth is investigated. Keeping all other parameters constant, the bandwidth remains nearly the same with increasing duty cycle and decreasing slope angle. Importantly, the results show a linear relationship between the duty cycle and slope angle of the large bandwidth MMDG. The trapezoidal MMDG designs can be obtained base on the linear relationship and a optimize rectangle grating result. A 200 nm bandwidth (from 700 nm to 900nm) MMDG with efficiency exceeding 90% is obtained using the method. This method can be effectively used in the design of pulse compression grating.

The laser damage resistance of the coatings for high-power laser systems depends greatly on the surface quality of the substrate. In our work, experimental approaches were employed to understand the interface coupling effect of the substrate surface and coatings on the laser resistance of the coatings. A 1064 nm anti-reflection (AR) coating was deposited by an e-beam coater onto fused silica with and without micro-scale pits (structural defects). The micro-scale pits were precisely fabricated by femtosecond laser processing to prevent the emergence of subsurface cracks. Different deposition temperatures were characterized in order to verify the intensity of the interface coupling effect of the substrate and coating layers. Our experimental results indicate that impurities that are introduced in the finishing process, shifted to the substrate surface, and aggregated during the heating process, play a much more crucial role than structural defects (length: ∼7 μm; width: ∼3 μm; depth: ∼0.8 μm) in the laser-induced damage process. By effectively reducing the intensity of the interface coupling effect, the e-beam AR coatings, whose laser-induced damage resistance was closed to the bare substrate, was prepared.

The multilayer ridge metal/multilayer-dielectric gratings (MMDGs) for pulse compressors show high efficiency, broad bandwidths, large fabrication tolerances and high laser-induced damage thresholds. The diffraction efficiency, bandwidth, and near-field distribution of the multilayer structure ridge MMDG are theoretically investigated. Simulation results show that the film structure of the grating ridge has a great influence on the bandwidth and near-field distribution. The maximum electric field is located in the high-index layer of the grating ridge with high -1st diffraction efficiency. As the thickness of the high-index layer decreases, the maximum electric field moves to the low-index layer of the grating ridge with. Base on the results, the sandwich ridge MMDG is an ideal pulse compression grating for chirped pulse amplification systems.

In this paper, metallic pulse compression gratings (MPCG) with three kinds of grating structures are manufactured. The diffraction efficiency and bandwidth of samples are measured and it can be found that the different grating structure has different diffraction efficiency and bandwidth. Laser damage tests of samples are implemented by an 800±30 nm laser at pulse duration of 31 fs and it can be also found that the different grating structure has different laser-induced damage threshold. Experimental measurements illustrate that the grating structure has a great influence on bandwidth, diffraction efficiency and damage threshold. The typical damage morphologies of MPCG reveal that the damage is induced by absorption and thermal stress.