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We report Si/SiO2 mirrors operating in the spectral range 2-3.2 um. The coatings exhibit reflectance exceeding 99.6% and provide group delay dispersion of (-100 fs2) and (-200 fs2.) The mirrors are key elements of Cr:ZnS/Cr:ZnSe femtosecond lasers and oscillators.

We developed broadband dichroic filters for pump-probe spectroscopy studying ultrafast dynamics of biological molecules. The filters operating at Brewster angle of ZnSe transmit mid-infrared and reflect near-infrared radiation. Thin-film material combinations were ZnS/YbF3 and Ge/YbF3.

The broadband dispersive mirror based on Si/SiO2 thin-film materials and providing group delay dispersion of -200 fs2 in the spectral range from 2 to 3.2 µm have been successfully developed and produced for the first time. The mirrors open a new avenue in the development of ultrafast optics operating in the infrared spectral range and push forward the ultrafast mid-infrared technology.

A new design approach allowing optimizing absorptance in an individual layer or in a group of layers of an optical coating is proposed. This approach can be used for designing multilayers for solar cells and other absorptive coatings.

We present a compact mid-infrared spectrometer employing a bright, phase-coherent, 100-MHz source spanning the wavelength region between 9 and 15 µm (at −30dB) and field-resolved detection via electro-optical sampling, with a dynamic range of 107.

An approach to developing an inhomogeneous thin film model is proposed and demonstrated for HfO2 and MgF2 single layers. The single layer models are then used to optimize the spectral performance of visible broadband antireflection coatings.

Production of polarizers for high-intensity applications based on ZrO2/SiO2 pair of thin film materials is discussed. A special type of direct broad band optical monitoring providing good manufacturing results is described.

A new class of multilayer synthesis problems is addressed. We consider changes of the electric field phase with respect to the pulse envelope after a reflection from a mirror and solve related multilayer optimization problems.

Design and production of multilayer optical coatings is considered as multi-stage integral problem. The combination of state-of-the-art design methods and modern deposition techniques advances coating performance to theoretical limits.

Here we report a highly-dispersive mirror with a group delay dispersion of -10000 fs2 for wavelengths 1025 -1035 nm. This allows power scaling in a 300-fs Yb:YAG oscillator.

Electro-optic sampling is a valuable tool in the terahertz range for sensitive, time-resolved electric field measurement. We show that this technique can be extended to the near infrared for unambiguous measurement of broadband, phase-locked pulses.

Design technique taking into account bulk inhomogeneity of coating layers directly in a course of designing is presented. Its application to two classes of design problems where effects of bulk inhomogeneity are essential is demonstrated.

Approach to solving all types of design problems in spectral regions from X-ray to EUV is presented. It employs the most efficient general design tools and special technique aimed at taking into account interface roughness.

Half-wave-hole problem, mainly caused by refractive index inhomogeneity of hafnia, had greatly influenced the spectra and application of HfO2/SiO2 dichroic laser mirrors. Two approaches to eliminate the half-wave-hole effect had been proposed.

We developed a method for group delay and group delay dispersion measurements, based on location of interference resonance peaks. Using simultaneous processing of the data acquired for different spacer distances we achieved high quality results.

Previously elaborated indirect monitoring strategy is modified in order to raise an accuracy of layer thickness monitoring. This strategy is applied for deposition of a specially chosen hot mirror design with no thin layers.

We propose a new numerical algorithm allowing one to design multilayer optical coatings which are stable to refractive index variations. Application of the algorithm is demonstrated using two practical design problems.

We study TiO2 films deposited at different substrate temperatures. The films are carefully characterized on the basis of in situ and ex situ measurements. The results will be useful for further laser-induced damage threshold investigations.

We apply a reliable reverse engineering approach for post-production characterization of an optical coupler. We perform reverse engineering on the basis of in situ data analysis and validate results using transmittance and group delay measurements.

A new synthesis technique allowing to design a set of robust designs is proposed. Efficiency of this technique is demonstrated using AR coating, hot mirror, and broadband filter design examples.

Indirect broadband optical monitoring can be successfully applied for the production of three-line minus filters. Pre-coating of witness substrates used to monitor low index layers raises an accuracy of depositions of these layers.

Definition of an error self-compensation mechanism associated with direct broadband optical monitoring is proposed and a research approach for studying this effect is developed. Existence of a strong error self-compensation is demonstrated for cold mirrors.

The design approach originally developed for WDM filters is applied for designing wide bandpass filters. Obtained multicavity filters can be successfully manufactured using turning point optical monitoring combined with quartz crystal monitoring.

A method for creating a database of dispersive refractive indices of thin film materials is outlined. Refractive indices for the most widely used metal oxide films produced under different deposition conditions are presented.

Pre-production estimations of manufacturing yields of several theoretical designs can be used for choosing the most manufacturable design. Practical application of such choice is demonstrated using designs with ramp spectral transmittance.

Using results of the probability theory, we estimate a number of computational experiments required for choosing the most manufacturable design with a sufficient confidence level. Experiments with broadband optical monitoring are used as examples.

Computational manufacturing experiments are used for estimating expected production yields and for choosing the most manufacturable design and respective optimal monochromatic monitoring strategy.

We propose an approach to the determination of thicknesses of individual coating layers from on-line monitoring data. We demonstrate an application of this approach to the analysis of the 52-layer filter.

We demonstrate the potentialities of our new optical monitor (OptiMon) to perform transmission measurements, re-engineering and recalibration of quartz monitor tooling factors during a deposition process. Examples include single layers as well as high-low stacks.

We propose direct monochromatic monitoring strategy that allows one to control each new coating layer independently of errors in previously deposited layers.

We propose a new scheme for obtaining multiple solutions to a design problem. Using hot mirror designs we demonstrate that this scheme can be used for choosing designs satisfying additional practical criteria of better manufacturability.

We demonstrate that comparative pre-production analysis of expected production errors can be useful for choosing the most practical design from a series of theoretical designs with various combinations of principal design parameters.

A new optical coating design algorithm using the equivalent layers theory is presented. The algorithm is based on the merit function constrained optimization in the accessible domain of equivalent phase thicknesses and equivalent refractive indices.

We present theoretical estimation predicting: maximum value of electric field inside multilayer-high-reflector cannot be reduced below value specified by refractive index of ambient medium and highest-layer refractive index. Estimation valid for high-reflecting-coating of arbitrary type.

The proposed automated monitoring approach is based on the ideas of the theory of inverse problems. Computer simulation proves the robustness of the approach and provides insight on the influence of measurement errors.

A simple relationship between the radiant energy transmittance and group delay in the passband region is established. This relationship is based on the consideration of complex poles of the amplitude transmittance.

A system for on-line characterization and reoptimization of evaporated hafnia/silica coatings has been developed, incorporating inhomogeneity of evaporated films and changes in properties between vacuum and air. Tests verify the capability of improving manufactured coatings.

Results of the optical characterization of dielectric thin films depend on the quality of experimental data. This work investigates the iinfluence of systematic errors in measurement data on the determination of thin film parameters.

The designing of WDM filters is a specific integer optimization problem. An automated approach to the design of such filters combines the ideas of classical design approaches with the advanced concepts of integer optimzation.

It is shown that large scale and small scale surface roughness harmonics impact the amplitude reflection and transmission coefficients of optical thin films in different ways. An effective calculation algorithm taking into account surface roughness effect is proposed.

To enable the enhancement of few-cycle pulses in high-finesse passive optical resonators, a novel complementary-phase approach is considered for the resonator mirrors. The design challenges and first experimental results are presented., 3 pages