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Spintronic metal thin films excited by femtosecond laser pulses have recently emerged as excellent broadband sources of terahertz (THz) radiation. Unfortunately, these emitters transmit a significant proportion of the incident excitation laser, which causes two issues: first, the transmitted light can interfere with measurements and so must be attenuated; second, the transmitted light is effectively wasted as it does not drive further THz generation. Here, we address both issues with the inclusion of a high-reflectivity (HR) coating made from alternating layers of SiO2 and Ta2O5. Emitters with the HR coating transmit less than 0.1% of the incident excitation pulse. Additionally, we find that the HR coating increases the peak THz signal by roughly 35%, whereas alternative attenuating elements, such as cellulose nitrate films, reduce the THz signal. To further improve the emission, we study the inclusion of an anti-reflective coating to the HR-coated emitters and find the peak THz signal is enhanced by a further 4%.

Chirped mirrors with porous top layer (CMPTL) feature broadband dispersion control. In this work, CMPTL for broadband spectral range was designed and deposited. Additionally, sensitivity of CMPTL spectral parameters to humidity in air was investigated.

The effectiveness of ultrashort pulse compression depends on the coatings group delay dispersion (GDD) characteristics in chirped mirror (CM)-based optical systems. Current porous-layer-based CMs with low GDD oscillations are limited to less than half optical octave spectral bandwidth and the stability of their spectral parameters is still unknown. In order to address these limitations, a broadband CM (covering 400 nm bandwidth) with a porous top layer was deposited and spectral parameters were measured at different environmental conditions. The modeled refractive index of the porous layer varied by approximately 1% due to the changes in humidity. Deposited coatings exhibited low sensitivity of GDD oscillations to deposition errors of porous layer and humidity in the surrounding environment.

A novel metal–dielectric three-layer cube broad-angle non-polarizing beam splitter (nPBS) with an ultrathin copper layer was designed, prepared and characterized. Our nPBS structure (270 nm thick) is optimized around the wavelength of 1064 nm (reflectance in between 25 and 35% and transmittance in between 55 and 65% for the incidence angle range of 35–55°). For comparison, a 24-layer design for 45° incidence angle solution (6193 nm thick) using dielectric–dielectric nPBS was shown. For manufacturing point of view, reducing the layer number in the coating let eliminate undesirable mistakes during preparation of every layer thickness and decrease the time of whole structure fabrication. During or after multilayer deposition it is necessary to minimize the possibility of metal oxidation by choosing material with low affinity to oxygen. Additionally, it is important to reduce the product price by avoiding more expensive metals like gold and silver. Our nPBS structure was prepared in a single process by using of magnetron sputtering. The measured transmittance and reflectance values are in agreement with the design and the target values. Every single layer thickness error analysis was done.

Laser damage resistance of a transparent optical component significantly depends on its substrate surface quality. In this work low energy oxygen plasma etching of fused silica (FS) substrates was investigated in terms of plasma ion energy and etching depth. Laser induced damage threshold (LIDT) and surface roughness of experimental samples were measured and compared. The LIDT of plasma treated uncoated FS substrate increased from 5.0 ± 0.3 J/cm2 up to 75 ± 4 J/cm2 for 355 nm laser ns pulses without any surface roughness deterioration. Anti-reflective (AR) optical interference coating for 355 nm wavelength was deposited on plasma etched and non-etched substrates. Measured LIDT of plasma etched and AR coated component was 3.4 times higher comparing to coated non-etched substrate case and reached 14 ± 0.7 J/cm2. These results demonstrate successful application of low energy oxygen plasma etching for improving laser induced damage performance of uncoated and AR coated fused silica substrate without deterioration of surface roughness. This application could be also successfully extended for production of other transparent high power UV laser optics like polarizers, beam splitters, etc.

Scandium oxide films were deposited on fused silica substrates by reactive pulsed DC magnetron sputtering. The use of feed-back optical emission monitoring enabled high-rate reactive deposition of films with tunable stoichiometry and properties. The under-stoichiometric, stoichiometric and over-stoichiometric scandium oxide films were prepared. The compressive stress in films was between 235 and 530 MPa. We showed that phase structure, density, surface roughness and optical properties of the scandium oxide are affected by the film stoichiometry and deposition conditions. Transparent scandium oxide films were slightly hydrophobic (94 ± 3°), homogeneous with a crystallite size of 20 ± 5 nm. The lowest extinction coefficient 0.7 × 10 −3 , the highest refractive index 2.08 (both quantities at the wavelength of 355 nm) and the highest density 4.1 ± 0.1 g cm −3 exhibited film prepared with the stoichiometric composition. Stoichiometric scandium oxide can be used in various optical applications as high refractive index and wide bandgap material. Transitions to under- or over-stoichiometry lead to a decrease of film density, refractive index and increase of the extinction coefficient.

The decrease of laser-induced damage threshold (LIDT) when exposed with high number of laser pulses is a well-known phenomenon in dielectrics. In the femtosecond regime this fatigue is usually attributed to the incubation of laser-induced lattice defects. In this work, a computational model is used to combine the data from time-resolved digital holographic microscopy measurements together with results of S-on-1 laser-induced damage threshold test in order to investigate fatigue of ZrO

Chirped mirrors covering 200 nm bandwidth were deposited for laser-induced damage threshold (LIDT) testing. Coating designs were optimized to achieve better LIDT performance. After LIDT testing morphology of damage sites was analyzed.

The total generated output power in high-power laser systems is mainly limited by the laser-induced damage phenomena in coated optics. A significant part of optics include high reflectivity coatings. A research was conducted for the development of advanced high reflectivity mirrors, capable to withstand extreme laser fluence and featuring spectral stability at different ambient conditions. A concept of combination of IBS and GLAD technologies was proposed and implemented to form a hybrid multilayer mirror for the 355 nm wavelength. An optical and structural properties were investigated to evaluate the advantages of both technologies. The relation between the number of sculptured silica layers and standard mirrors performance under the high power of laser radiation was determined. The results of analysis show an improved reflectivity and optical resistance of consolidated coatings. LIDT measurements indicate the potential of reaching 90 J/cm2 for 355 nm wavelength (pulse duration 2.5 ns) while maintaining the reflectivity value higher than 99.5%. New findings indicate the superiority of hybrid coatings if compared to both classical and all-silica coatings. This knowledge opens up the new possibilities in further development of extreme light sources.

Back-side coated (BASIC) chirped mirror is characterized by very smooth group delay dispersion (GDD) curve over extremely wide spectral bandwidth. However, these optical elements suffer from poor flatness since they combine as thin as possible substrate and highly stressed sputtered coating. Several stress compensating techniques may be combined to produce fully stress-compensated BASIC chirped mirror. Ion beam sputtering technology was used to deposit BASIC chirped mirror based on Nb2O5/SiO2 mixtures and post-deposition annealing was implemented to compensate coating stress and fabricate optical element with sufficient flatness. Chirped mirror for 150 nm wavelength range and −300 fs average GDD was deposited on 0.35 mm thickness substrate. Final optical element featured initial flatness of uncoated substrate and close to maximum achievable GDD, considering coating thickness and wavelength range.

Standard high reflectivity coatings consist of materials with high and low refractive indexes. Typically, optical resistivity of such elements is limited by the threshold value of material with high index. Combination of two deposition methods, namely ion-beam sputtering and oblique angle deposition, was used to form high reflectivity coatings for the wavelength of 355 nm. Variation of the design of standard coating and the number of top layers, deposited at oblique angle have been investigated. Laser induced damage thresholds, optical scattering, surface roughness, spectral performance etc. were tested for the experimental samples. Analysis indicate that combination of both deposition methods allows to enhance the optical resistivity of typical high reflictivity mirrors. Introducing standard method also allows to stabilize the spectra and reduce the losses of total optical component.

Standard high reflectivity mirrors consist of layers with high and low refractive indexes. Typically, optical resistivity of such elements is limited by the threshold value of material with high index. Combination of two deposition methods, namely ion-beam sputtering and glancing angle deposition, was used to form high reflectivity mirrors for the wavelength of 355 nm. Variation of the design for standard coating and the number of top layers, deposited at oblique angle have been investigated. Laser induced damage thresholds, surface roughness, spectral performance etc. were tested for all the experimental samples. Analysis indicate that combination of both deposition methods allows to enhance the optical resistivity of typical high reflictivity mirrors. Fully sculptured thin film based mirrors also exhibit spectral instability and optical losses. Introducing standard method allows to stabilize the spectra and reduce the losses of total optical component.

This paper investigates niobia/silica mixed oxide thin films deposited by reactive pulse-DC/RF magnetron co-sputtering of Nb and Si metal targets at room temperature. The reactive gas flow during the sputtering processes was either controlled by direct mass flow rate (i.e. constant reactive gas flow) or by an active feedback process control system. 61% and 137% higher deposition rates of Nb2O5 and SiO2 layers, respectively, were obtained using the latter technique as compared to constant reactive gas flow. Films exhibited bulk or near-bulk density. All mixture films produced in this study had an amorphous structure. A volume law of mixtures was used to determine the coating composition. It is shown that the fraction of SiO2 or/and Nb2O5 has a linear dependency on sputter target power density. On this basis, rugate filter coating designs can be easily deposited, where refractive index gradually varies between that of pure Nb2O5 and pure SiO2. Substantially less inhomogeneity of coating mixtures was found in films produced using a reactive sputtering process with feedback-control.

Laser induced damage of optical coatings has been one of the most important targets during many decades of intensive research. Different techniques were used and explored with the aim to increase the resistance of multilayer systems to laser pulses. In this work, LIDT results of different “base” structures made by ion beam sputtering of Al2O3, SiO2 and their mixtures are presented, and further enhancement possibilities are discussed by applying additional layer structure using higher bandgap material – fluorides and glancing angle deposited SiO2.

Band-gap and refractive index are known as fundamental properties determining intrinsic optical resistance of multilayer dielectric coatings. By considering this fact we propose novel approach to manufacturing of interference thin films, based on artificial nano-structures of modulated porosity embedded in high band-gap matrix. Next generation all-silica mirrors were prepared by GLancing Angle Deposition (GLAD) using electron beam evaporation. High reflectivity (HR) was achieved by tailoring the porosity of highly resistant silica material during the thin film deposition process. Furthermore, the proposed approach was also demonstrated to work well in case of anti-reflection (AR) coatings. Conventional HR HfO2 and SiO2 as well as AR Al2O3 and SiO2 multilayers produced by Ion Beam Sputtering (IBS) were used as reference coatings. Damage performance of experimental coatings was also analyzed. All-silica based GLAD approach resulted in significant improvement of intrinsic laser damage resistance properties if compared to conventional coatings. Besides laser damage testing, other characteristics of experimental coatings are analyzed and discussed – reflectance, surface roughness and optical scattering. We believe that reported concept can be expanded to virtually any design of thin film coatings thus opening a new way of next generation highly resistant thin films well suited for high power and UV laser applications.

In this paper, the relation between the laser-induced damage threshold (LIDT) and the electric field intensity (EFI) distribution inside a CM is investigated experimentally. We show that it is possible to increase the LIDT values by slightly modifying the electric field of a standing wave distribution without loss of spectral and dispersion performance. Suggested CM design improvement could increase reliability and LIDT performance of both CM elements and high-power systems they are used in.

The decrease of laser-induced damage threshold (LIDT) when exposed with high number of laser pulses is a well-known phenomenon in dielectrics. In the femtosecond regime this fatigue is usually attributed to the incubation of laser-induced lattice defects. In this work, a computational model is used to combine the data from time-resolved digital holographic microscopy measurements together with results of S-on-1 laser-induced damage threshold test in order to investigate fatigue of ZrO 2 single layer coating. Two distinct damage modes were identified and shown to follow different fatigue behaviors: formation of catastrophic damage is highly nonlinear in time, while incubation of color-change mode appears to be linear in time.

The nonlinear LBO (LiB3O5) crystal is widely used in many Nd : YAG, Yb : KGW and Nd : YLF lasers in order to generate higher optical harmonics. However, the most limiting factor in such applications is the optical resistance of their coated surfaces described by the so-called Laser Induced Damage Threshold (LIDT) parameter. In this work we investigate the “fatigue” (multi-pulse) behaviour of LIDTs in LBO crystals coated with different types of (single AR@355 nm and triple AR@355+532+1064 nm wavelength) anti-reflective coatings while optimising the refractive index designs and selecting appropriate sub-layer materials. All the coatings were produced of different oxide materials (ZrO2, Al2O3, SiO2) and ZrO2-SiO2 mixtures by using the ion beam sputtering (IBS) deposition technique. The optical damage resistance of both fixed and transient refractive index coatings is of special interest. Besides the spectral properties, the resistance to laser irradiation is characterised at the wavelength of 355 nm with laser pulses of nanosecond duration. The conclusions are drawn about the AR coated LBO with the most successful designs by the means of optical resistance.

We present the flat focusing mirror - the dielectric mirrors capable to focus and image the narrow beams in reflections. The mirrors are flat, and transversally invariant, i.e. have no optical axis. We consider two different configurations of such mirrors: 1) Bragg-like mirrors, consisting of structure of specially designed dielectric layers; 2) periodically modulated surface on a subwavelength scale. We also discuss the combined case - the longitudinally chirped photonic crystals.

We present results obtained during investigation of synchronously pumped optical parametric oscillator (SPOPO) with broadband complementary chirped mirror pairs (CMP). The SPOPO based on β– BBO nonlinear crystal is pumped by second harmonic of femtosecond Yb:KGW laser and provides signal pulses tunable over spectral range from 625 to 980 nm. More than 500 mW are generated in the signal beam, giving up to 27 % pump power to signal power conversion efficiency. The plane SPOPO cavity mirror pairs were specially designed to provide 99 % reflection in broad spectral range corresponding to signal wavelength tuning (630–1030 nm) and to suppress group delay dispersion (GDD) oscillations down to ±10 fs 2 . Dispersion properties of designed mirrors were tested with white light interferometer (WLI) and attributed to the SPOPO tuning behaviour.

Recently, the principle of flat focusing based on one-dimensionally chirped dielectric mirrors has been proposed and experimentally demonstrated. The flat chirped mirror causes anomalous diffraction of the beam during reflection, opposite to the normal diffraction in free space propagation. The anomalous diffraction compensates the normal diffraction of the beam resulting in focusing after reflection. For a better focusing performance and for a larger near-field focal distance, a stronger anomalous diffraction is required. We show that the anomalous diffraction can be enhanced by introducing a defect layer in the chirped mirror, as the structure becomes similar to a Gires-Tournois interferometer. The focal distance can be substantially increased due to the defect layer. In our specific structure, the focal distance shows an increase from 19 to 39 mu m, numerically.

The laser damage resistance of an optical element in high power laser systems depends significantly on the surface quality of the optical substrate. In this experiment, commercially polished fused silica substrates were etched in argon plasma generated by a RF source and their surface roughness, flatness and optical properties were investigated. This method can be applied in a vacuum chamber prior to deposition of the multilayer coatings without breaking the vacuum. It was shown that by etching the resistance to 355 nm, laser radiation could be improved more than 8 times. However, it strongly related with primary substrate quality. The etching depth from 100 nm suggests the optimum performance of surface quality in terms of surface low roughness, high flatness, and high laser damage threshold. These results are of significant importance for the manufacture of high quality laser optics on fused silica substrates. As an example of an application of our technology, anti-reflective and polarizing optical interference coatings were deposited on etched substrates and the increase of their resistance to laser radiation was measured.

In this work we report an experimental investigation of subsurface damage (SSD) in conventionally polished fused silica (FS) substrates which are widely used in laser applications and directly influence performances of optical elements. Two procedures were developed: 1 – acid etching and 2 – superpolishing. Additionally, surface roughness and total integrated scattering (TIS) measurements were performed to find correlation between the main surface properties and laser induced damage threshold (LIDT) as circumstantial evidence of elimination of SSD. Different durations of acid etching have been used to study LIDT of FS substrates. These experiments revealed that the optimal etching time is ~1 min. for a given acid concentration. Laser induced damage threshold of etched and SiO2 layer coated FS samples increased ~3 times, while of the ones that were not coated - 4 times. It has been revealed that for nonetched surface a single nano- to micro-scale absorbing defect ensemble most likely associated with polishing particles within Beilby layer was dominant, while damage morphology in ~1 min etched FS sample had no point defects observed. More than 5 times lower roughness value (RMS) was obtained by superpolishing procedure using colloidal silica abrasive particles. LIDT of such superpolished fussed silica substrates was also strongly increased and compared with conventional CeO2 abrasive polishing.

In the past years the usage of mixed oxides coatings lead to an important improvement of laser damage threshold and quality of optical elements. In this study influence of post treatment procedure - ex-situ annealing - is examined in terms of quality, optical constants and laser induced damage threshold (LIDT) of mixed HfO 2 and SiO 2 coatings. Monolayer thin films containing different fractions of HfO 2 are deposited with ion beam sputtering technology (IBS.) All samples are post annealed at different temperatur es and optimal regimes are defined. Re fractive index and absorption coefficient dispersion is evaluated from transmission spectra measurements. Surface roughness of all samples is characterized before and after deposition and annealing, using atomic for ce microscopy (AFM). Microstr uctural changes are identified from changes in surface topography. Furt her, optical resistance was characterized by 5.7 ns duratio n pulses for 355 nm wavelength laser radiation, performing 1-on-1 sample exposure tests with high resolution micro-focusing approach for monolayer samples and S-on-1 tests for multilayer reflectors. Morphology of damaged sites was analyzed through optical microscopy. Finally, conclusions about annealing effect for mixed HfO

We propose and demonstrate a novel functionality of chirped mirror for monochromatic light beams: a diffraction control in reflections resulting in focusing or imaging of beams. The chirped mirrors, commonly used for manipulating temporal profiles of pulses, here are applied for manipulating the spatial dispersion of a monochromatic beam. By penetrating into dielectric layers of chirped mirror, the monochromatic beam experiences the negative diffraction, therefore the beam diverge propagating in front and behind the structure in normal diffraction region can be compensated inside this structure with negative diffraction. The result is focusing or imaging of the reflected beam from a flat interface of chirped mirror without optical axis.

Y. C. Cheng,1 M. Peckus,2 S. Kicas,2 J. Trull,1 C. Cojocaru,1 R. Vilaseca,1 R. Drazdys,2 and K. Staliunas1,3 1Departament de Fisica i Enginyeria Nuclear, Universitat Politecnica de Catalunya, Colom 11, 08222 Terrassa, Barcelona, Spain 2Center for Physical Sciences and Technology, Savanoriu Ave. 231, LT-02300, Vilnius, Lithuania 3Institucio Catalana de Recerca i Estudis Avancats (ICREA), Pg. Lluis Companys, 23, 08010 Barcelona, Spain (Received 21 December 2012; published 15 April 2013)

Optical and physical properties of magnetron sputtered Nb2O5-SiO2 mixtures are reported. Deposition rate and properties of mixtures produced were improved significantly by using fast feedback reactive sputtering process control.

Despite the growing improvement in optical polishing and deposition technologies optical resistance of the laser components used for high-power UV applications remains insufficient in many cases. In this study influence of different fused silica substrate preparation, post treatment processing and de position techniques are exam ined in terms of surface roughness, optical scattering and laser damage performance. The conventional techniques of polishing, etching, and finally surface cleaning of substrates have been investigated. Further, a part of samples were also coated with SiO 2 monolayer by Ion Beam Sputte ring (IBS) technique. Su rface quality was characterized prior to and after the treatment and deposition processes by the means of total integrated scattering (TIS) and atomic force microscopy (AFM). The experimental results of surface roughness measurements exhibited a good correlation between AFM and TIS methods. Further optical resistance was characteri zed with 10 ns duration pulses for 355 nm wavelength laser radiation performing 1-on-1 sample exposure test with high resolution micro-focusing approach. A dominating damage precursor ensembles produced during manufacturing processes were identified and directly compared. Finally, the conclusions about the quality influencing factors of investigated processes were drawn. Keywords: laser damage threshold, total integrated scattering, polishing, cleaning, etching, coating, ion-beam sputtering.

In this work, the influence of using ion beam sputtered mixtures instead of pure materials and the impact of applied post deposition annealing to residual stress is investigated. Single layer pure films and mixtures of Nb2O5 / SiO2 as well as multilayer coatings are examined by the means of residual stress. High residual compressive stress was measured for all as-deposited samples. Pure and mixed monolayer samples were annealed at various temperatures and residual stress was determined after each annealing routine. Residual changes in optical constants, layer thickness and surface roughness upon annealing are examined to explain stress behavior. Obtained data was used to make optimization of high reflectivity structures with completely eliminated residual stress. The proposed method can be used to coat very thin substrates where flatness requirements are essential.

We report on the laser damage resistance of thin films prepared by Ion Beam Sputtering. The samples are fused silica substrates coated with single layer films of pure oxides (SiO 2 , Nb 2 O 5 , ZrO 2 , HfO 2 , Ta 2 O 5 , Al 2 O 3 , Sc 2 O 3 ) and oxide mixtures with various ratios (Nb 2 O 5 /SiO 2 , ZrO 2 /SiO 2 , HfO 2 /SiO 2, Ta 2 O 5 /SiO 2 , Al 2 O 3 /SiO 2 and Sc 2 O 3/ SiO 2 ). For this study the LIDT of more than 60 different samples have measured at 1030nm with pulse durations of 500fs with single pulse irradiation. The results are expressed and compared in terms of LIDT as a function of the measured band gap energy and refractive index. For simple oxide materials a linear evolution of the LIDT with bandgap is observed, with the exception of Sc 2 O 3 material where a very high damage threshold is observed, compared to other high index materials. In the case of mixtures, a more complex behavior is evidenced.

Mixed metal oxide coatings of ZrO2 / SiO2 , and Nb2 O5 / SiO2 as well as films of pure SiO2 , ZrO2 and Nb2 O5 have been prepared by the Ion Beam Sputtering (IBS) technique and characterized on their physical properties. The Laser-Induced Damage Thresholds (LIDT) of these samples have been measured at 1064 nm with the 1-on-1 mode in the nanosecond regime. The optical resistance results obtained from laser damage probability curves indicate a decrease of the LIDT in both sets of the mixtures when the content of the high index material is increased. By comparing the LIDT to the bandgap values (Eg) that have been measured, a dependence of LIDT to Eg is evidenced. Following these results, comparisons are made with the case of 500fs LIDT that have been measured on the same samples. It is found that the same behavior is observed on both cases (ie LIDT dependence with Eg). Discussions are then conducted on the possible physical mechanisms to explain the results and it is found that in the case of the nanosecond regime, the LIDT dependence on Eg can be explained by a critical temperature reached during the laser damage process that exhibit a dependence on the band-gap of the material. The influence of the film thermal conductivity on the values of the critical temperature is studied.

Summary form only given. We explore reflections of narrow beams from one-dimensionally modulated photonic structures, where the modulation period varies across the structure (the so called chirped dielectric mirrors). It is known, that the plane waves reflected in a normal direction from the chirped mirrors, can show modified temporal dispersion [1]. Different frequency components reflect from the different depth of the structure, as illustrated in Fig. 1a. As a consequence the pulses reflected from such mirrors can obtain a chirp, or contrarily, a pulse chirp of opposite sign can be compensated and eliminated by reflection. We argue, that the character of reflection of narrow beams can be also peculiar from such a chirped structure. The plane wave components of the beam also reflect from the different depth of the structure (see illustration in Fig. 1b), which can result in modification of the spatial dispersion. The beam, in this way could obtain important spatial transformations during reflections. In particular a focalisation of the beam could be possible under particular conditions, as illustrated in Fig. 1c.

We report on the laser damage resistance of ion beam—sputtered oxide materials (Al2O3, Nb2O5, HfO2, SiO2, Ta2O5, ZrO2) and mixtures of Al2O3-SiO2, Nb2O5-SiO2, HfO2-SiO2, Ta2O5-SiO2, and ZrO2-SiO2, irradiated by single 500 fs pulses at 1030 nm. Laser-induced damage threshold (LIDT), refractive index, and bandgaps of the single-layer coatings are measured. For pure oxide materials a linear evolution of the LIDT with bandgap is observed. The results are in accordance with our simulations based on photo-ionization and avalanche-ionization. In the case of mixtures, however, deviations from the previous behaviors are evidenced. The evolution of the LIDT as a function of the refractive index is analyzed, and an empirical description of the relation between refractive index and LIDT is proposed.

We present the investigation of a synchronously pumped optical parametric oscillator (SPOPO) based on beta barium borate (BBO) nonlinear crystal with broadband complementary chirped mirror pairs (CMPs). Three SPOPO cavity configurations with slightly different intracavity dispersion were explored. Dispersion properties of cavity mirrors were characterized using a white light interferometer and found to be the key factor determining the gap-free tuning range as well as simultaneous multiwavelength generation. The SPOPO is pumped by the second harmonic of a Yb:KGW oscillator and provides signal pulses tunable over a spectral range from 625 to 980 nm. Signal pulse duration ranges from 102 to 268 fs in various intracavity dispersion regimes. In addition, signal beam power in excess of 500 mW is demonstrated, corresponding to 27% conversion efficiency from pump to signal wave.

We report an experimental investigation in the laser-induced damage threshold (LIDT) of optical coatings materials. The samples are single layers of Al2O3, Nb2O5, HfO2, SiO2, Ta2O5, ZrO2 deposited through different deposition techniques (evaporation or sputtering with/without ion assistance) and mixtures of Al2O3/SiO2, Nb2O5/SiO2, HfO2/SiO2, Ta2O5/SiO2 and ZrO2/SiO2 on silica substrates. The LIDT is measured at 1030nm, 500fs in single shot mode. The results are expressed and compared in term of LIDT as a function of bandgap and LIDT as a function of refractive index.

ZrO2-SiO2 and Nb2O5-SiO2 mixture coatings as well as those of pure zirconia (ZrO2), niobia (Nb2O5), and silica (SiO2) deposited by ion-beam sputtering were investigated. Refractive-index dispersions, bandgaps, and volumetric fractions of materials in mixed coatings were analyzed from spectrophotometric data. Optical scattering, surface roughness, nanostructure, and optical resistance were also studied. Zirconia-silica mixtures experience the transition from crystalline to amorphous phase by increasing the content of SiO2. This also results in reduced surface roughness. All niobia and silica coatings and their mixtures were amorphous. The obtained laser-induced damage thresholds in the subpicosecond range also correlates with respect to the silica content in both zirconia- and niobia-silica mixtures.

In this study, we report on our recent progress in research of single layer mixed zirconia-silica and niobia-silica composite coatings prepared by Ion Beam Sputtering technique. All coatings of the same optical thickness were characterized in terms of reflection/transmission spectrometry, X-ray diffraction, atomic force and optical microscopy, optical back-scattering and optical resistance (laser-induced damage threshold - LIDT) in subpicosecond mode. The optical resistance, TIS and LIDT results reveal clear dependence on high refractive index material content in composite coating and its crystalline structure. The results are interpreted and discussed by the means of different models available in literature.

In this study, we present our recent progress in research of mixed zirconia/silica and niobia/silica coatings prepared by Ion Beam Sputtering technique. Single-layer coatings of the same optical thickness were characterized with respect to LIDT.

A novel application of chirped dielectric mirrors for narrow beam focalization is proposed and demonstrated numerically and experimentally. Analogy to temporal dispersion compensation by chirped dielectric mirrors is discussed.

A novel use of chirped mirrors for narrow beam focalization is proposed. Focusing in reflection from flat chirped mirror has been demonstrated numerically and experimentally. Analogy to temporal dispersion mirrors is discussed.