Method for the synthesis of semitransparent wide band dielectric mirrors

A general method for the numerical design of wide band dielectric mirrors with non-zero transmission is given. The values of the optical parameters for twenty mirrors designed by this method are presented and discussed.     

Theory of quarter-wave-stack dielectric mirrors used in a thin fabry-perot filter

I present a new derivation of the analytic form for the phase shift near resonance and the optical penetration length upon reflection from a distributed dielectric mirror consisting of a quarter-wave stack. The requirement of proper termination to achieve high reflectivity is suspended to investigate large optical penetration depths. Separate equations, derived for N and N + 1/2 layer pairs, are convenient for the design of tunable Fabry-Perot filters with a specified tuning range. The analysis is also applicable to distributed Bragg reflectors, vertical-cavity surface-emitting lasers, and resonant photodiodes. I show that the penetration length can sharply reduce the overly broad free spectral range of an ultrathin Fabry-Perot filter that might be useful in applications such as tunable wavelength filters for wavelength division multiplexing applications. The results also demonstrate regimes of zero dispersion and of superluminal reflection in the dielectric mirrors, which are of particular interest in photonic bandgap structures.     

Resonant frequencies of Fabry-Perot interferometers with ultrathin mirror spacings

Fabry-Perot interferometers (FPIs) with multilayer dielectric mirrors and mirror spacings as low as 0.7% of the operating wavelength are studied. It is shown how these low-order FPIs are affected by the phase dispersion characteristics of multilayer dielectric mirrors. Because experimental results in the optical regime are extremely difficult to obtain, radio frequency experiments are performed with coaxial cable FPI structures. Experimental results show excellent agreement with theory. These phase effects in FPIs with ultrathin mirror spacings are of great interest in the design of tunable microcavities with possible applications in optical communications.     

Extension of the velocity detection range of a tracking novelty filter that uses LiNbO(3) and strontium barium niobate

A method for extending the velocity range of motion detection by an optical tracking novelty filter is described. Separate photorefractive crystals are used as phase-conjugate mirrors in a phase-conjugate Michelson interferometer. Such an arrangement can ensure a significant difference in response times between the two arms of the interferometer, so that the range of detectable velocity is greatly reduced. Also, this implementation of a tracking novelty filter does not require a lossless dielectric beam splitter.     

Thermally invariant dielectric coatings for micromirrors

Thermal expansion-induced curvature becomes a major effect in micromirrors as the mirror diameter exceeds 100 microm. Such mirrors are used for optical switching, scanning, and many other applications. By using multilayer coatings instead of a single metal reflector, one can use the mechanical properties of the multilayer to create mirrors with zero curvature across temperature. We demonstrate the fabrication of such thermally invariant mirrors using dielectric coatings. A semianalytic model based on free-plate elastic theory is developed that uses empirical parameters in place of the true thermal expansion coefficients of the coating materials. Micromirrors are demonstrated that maintain their design curvature to within lambda/60 for lambda = 633 nm across an operating range from 21 degrees C to 58 degrees C.     

A Microwave Bandpass Filter on Dielectric Layers with Metal Grids

A bandpass filter of new design comprising dielectric layers with surface metal grids is developed and studied. Dielectric layers act as half-wave resonators, while metal grids act as mirrors with preset reflectivity and ensure optimum coupling between adjacent resonators and between the boundary resonators and free space. A test prototype of the third-order filter with a central bandpass frequency of ~12 GHz and relative bandwidth ~17% showed good agreement of theory and experiment. The proposed design can be used in making panels radio-transparent within a preset bandwidth for covering microwave antennas.     

Unraveling mirror properties in time-delayed quantum feedback scenarios

Abstract

We derive in the Heisenberg picture a widely used phenomenological coupling element to treat feedback effects in quantum optical platforms. Our derivation is based on a microscopic Hamiltonian, which describes the mirror-emitter dynamics based on a dielectric, a mediating fully quantized electromagnetic field and a single two-level system in front of the dielectric. The dielectric is modelled as a system of identical two-state atoms. The Heisenberg equation yields a system of describing differential operator equations, which we solve in the Weisskopf–Wigner limit. Due to a finite round-trip time between emitter and dielectric, we yield delay differential operator equations. Our derivation motivates and justifies the typical phenomenologicalassumed coupling element and allows, furthermore, a generalization to a variety of mirrors, such as dissipative mirrors or mirrors with gain dynamics.     

Ultrahigh-efficiency, very narrowpassband, tunable optical filter

Recently developed technologies have been uniquely integrated to produce optical filters with unprecedented performance. The precise design and fabrication of narrow-passband and high-efficiency optical filters with a central frequency of 532 nm are reported. Measurements with these filters demonstrate a performance that accurately mirrors the design specification, with one filter having a passband of 70 pm and an efficiency greater than 90% and the second filter having a passband of 7 pm and an efficiency greater than 80%.     

Leaky polarizing beam splitter with adjustable leak ratio for operation in the wavelength range of 440-690 nm

We discuss the optomechanical design and fabrication of a novel wideband (440-690-nm), leaky polarizing beam splitter with an adjustable leak ratio. This beam splitter is an important component of a multiwavelength dynamic testbed that we have constructed for testing optical disks. The multilayer thin-film structure of the beam splitter is essentially a stacked pair of narrow-band dielectric reflectors that have been fine tuned for optimal performance. The characteristics of the fabricated device are in good agreement with our theoretical calculations.     

1D-photonic crystals prepared from the amorphous chalcogenide films

We describe the preparation and optical properties of the 15-layer chalcogenide dielectric mirrors with the first order stop bands in near infrared range. The high refractive index Sb–Se and low refractive index Ge–S layers were deposited on silicon and glass substrates using thermal evaporation method. To centre the stop bands of the prepared chalcogenide mirrors at 1.55 μm, the layer thicknesses, d(Sb–Se) = 117 and d(Ge–S) = 183 nm, were calculated from the quarter wave stack condition. The optical reflectivity measurements revealed the total reflection from the 15-layer chalcogenide mirrors in the range of 1,400–1,600 nm for the unpolarized light with normal incidence. The effect of annealing on the optical properties of the prepared chalcogenide mirrors was studied as well. Using spectral ellipsometry, we examined the angular dependence of the multilayers reflectivity for the light with s- and p-polarization. The preparation of the dielectric mirrors for near infrared region from chalcogenide films seems to be possible exploiting good optical quality of chalcogenide films and their simple deposition.     

Optical range microcavities and filters using multiple dielectric layers in metal-insulator-metal structures

We present a technique to adjust omnidirectional resonances in planar metallic microcavity structures. It is demonstrated numerically with realistic material parameters that by changing the thickness of different dielectric layers in metal-dielectric-metal structures, the omnidirectional resonance can be chosen to lie at an arbitrary frequency in the optical range. These ideas can also be applied to design a high-pass filter in the optical frequency range.     

Chromospheric Helium Imaging Photometer (an Instrument for High Time Cadence 1083-nm Wavelength Solar Observations)

The scientific motivation, design criteria, and specifications for a new ground-based instrument to observe the Sun in the He i 1083-nm spectral line is described. The instrument employs a liquid-crystal tunable Lyot-type spectral filter and an array detector that allows the full solar disk to be observed with a time cadence of minutes. We describe the telescope's optical and mechanical features and discuss computer interface and data-reduction procedures employed. Instrument performance during the initial year of operation of the telescope at its high-altitude site is summarized.     

Designs and investigations of anti-glare blue-tint side-view car mirrors

Recent developments for luxury car industries have been in favor of anti-glare color-tint side-view exterior car mirrors. In this study, we explore the designs, the fabrications, and the investigations of anti-glare blue-tint samples suitable for the side-view car mirrors. With an aid of the thin film design software, the TiO₂-based backside-coated optical systems are prepared by the homemade and the retailed sputtering systems, and examined for the reflection spectra and the chromaticity diagrams. From four major designs of the anti-glare blue-tint mirrors, the ultra-thin metallic layer and the dielectric stack with the bottommost reflective layer offer the blue-tint at 85% highest reflection. Although the design requires only 40 min of the deposition time, the careful control of the ultra-thin metallic film thickness is crucial.     

Properties of Laser Mirrors at Non-normal Incidence

For laser mirrors made out of lossless periodic dielectric mutlilayers, having a basic period of two layers (ZnS and MgF₂) with different refractive indices and equal effective optical thicknesses, both the reflectivity at the stopband centre and the width of the stopband are calculated as a function of the angle of incidence for radiation polarized perpendicular or parallel to the plane of incidence. The results of computer calculations for mirrors with up to 20 layers are presented in a number of graphs and are discussed in detail. The graphs simplify the design of laser mirrors according to prescribed specifications and make it possible to distinguish between a maximum or a minimum of the spectral reflectivity at the centre of the stopband.     

Determination of refractive indices of quarter-wavelength Bragg reflectors by reflectance measurements in wavelength and angular domains

We show that all the structural properties of periodic dielectric multilayers can be accurately determined by a combined measurement of the transmission as a function of the wavelength and of the reflection as a function of the angle of incidence when the wavelength of the incident light is fixed. This method is applied to determine the structural properties of two commercial dielectric mirrors, and the results obtained are compared with a measurement of the same structural parameters by use of another technique based on the more standard optical guiding method.     

Dielectric mirrors for high power laser applications

Development of low loss dielectric high reflecting mirrors for high power laser applications presents some problems in selecting suitable thin film materials and in understanding their optical constants. Some of these problems have been solved by a systematic study of the dependence of optical constants on different evaporation parameters for a number of thin film materials. Using the data thus obtained high reflecting dielectric mirrors for different laser applications in theuv, visible and near-infrared regions were successfully developed indigenously by the method of vacuum evaporation.     

Design of multilayer extreme-ultraviolet mirrors for enhanced reflectivity

We show numerically that the reflectivity of multilayer extreme-UV (EUV) mirrors tuned for the 11-14-nm spectral region, for which the two-component, Mo/Be and Mo/Si multilayer systems with constant layer thickness are commonly used, can be enhanced significantly when we incorporate additional materials within the stack. The reflectivity performance of the quarter-wavelength multilayers can be enhanced further by global optimization procedures with which the layer thicknesses are varied for optimum performance. By incorporating additional materials of differing complex refractive indices-e.g., Rh, Ru, Sr, Pd, and RbCl-in various regions of the stack, we observed peak reflectivity enhancements of as much as ~5% for a single reflector compared with standard unoptimized stacks. We show that, in an EUV optical system with nine near-normal-incidence mirror surfaces, the optical throughput may be increased by a factor as great as 2. We also show that protective capping layers, in addition to protecting the mirrors from environmental attack, may serve to improve the reflectivity characteristics.     

Tunable Bragg filters based on polymer swelling

We report on the optical properties of Bragg mirrors and filters fabricated from photo-cross-linked standard optical polymers. The transmittance spectra of these devices in the visible to near-infrared spectral range were measured. We demonstrate efficient tuning of the filter peak of the polymer Bragg filters over several hundred nanometers by adding organic solvents to the surrounding atmosphere of the filter. This represents what we believe to be a novel tuning principle for Bragg filters relying on the use of polymeric materials.