Design and fabrication of As2S3-based non-quarterwave multi-cavity Fabry-Perot filters with the laser-adjustable central wavelength.

We present a thorough study of the use of As2S3 thin films for the fabrication of high-performance multi-cavity bandpass filters. We show that such layers can be used inside a non-quarterwave multi-cavity Fabry-Perot structure to produce local changes of the central wavelength of the filter using photosensitive properties of this material. In particular, we study the impact of these index changes on the spectral performances of the filters and show how to adapt the design of the Fabry-Perot structures to produce a spectral shift without degrading the bandpass profile. Double- and three-cavity Fabry-Perot filters are theoretically and experimentally studied.

In-situ interferometric monitoring of optical coatings.

We present a new method for the in situ measurement of the amplitude and phase of the reflection coefficient of a plane substrate installed in a mechanical holder rotating at high speed (120 turns per minute) during the deposition of optical thin films. Our method is based on digital holography and uses a self-referenced scheme to cancel the effects of the severe constraints generated by the vibrational and thermal environment of the deposition machine.

Angularly tunable bandpass filter: design, fabrication, and characterization.

We present a thorough study of a bandpass filter for the near-infrared (IR) region, with bandwidth below 20 nm, high transmission, and a broad rejection band [350-1100] nm. This filter is angularly tunable between 0 and 50° and shows a shift of the central wavelength from 970 nm down to 880 nm, without major changes in its bandwidth and spectral shape for unpolarized light. We first provide a description of the design procedure and then carry out an experimental demonstration by using plasma-enhanced reactive magnetron sputtering. We finally present an accurate characterization of this class of filter by using a custom optical system.

High-performance thin-film optical filters with stress compensation.

We present a thorough description of high-performance thin-film optical filters with high flatness. These components can combine several tens or hundreds of layers and are manufactured using plasma-assisted reactive magnetron sputtering. Stress compensation is achieved using dual-side coatings with appropriate spectral function. Examples are described of highly reflecting mirrors at 515 nm with 15 nm flatness peak-to-valley up to and over 75 mm diameter aperture, narrow bandpass filters, and filters with broadband controlled transmission.

Trinary mappings: a tool for the determination of potential spectral paths for optical monitoring of optical interference filters.

An alternative new technique for the determination of efficient optical monitoring strategies of optical interference filters is presented. This technique relies on the analysis of optical monitoring signals for different optical monitoring wavelengths and the comparison of these signals with some pre-defined criteria in order to generate potential spectral paths compatible with a dedicated trigger point monitoring technique. Trinary mappings are then generated in order to determine possible optical monitoring strategies. This technique is finally implemented on various filter designs and experimentally validated.

Use of a broadband monitoring system for the determination of the optical constants of a dielectric bilayer.

This paper extends a method previously applied to the determination of the optical constants of a high-index thin film to a dielectric bilayer. This method is based on the time recording of the spectral transmittance of the stack during its deposition with the help of an in situ broadband monitoring system.

Coating stress analysis and compensation for iridium-based x-ray mirrors.

Iridium-based coatings for mirrors of x-ray telescopes are studied. In particular, stress-induced deformation is characterized and shown to be compressive and equal to -1786 MPa. Two methods for stress compensation are then studied. One relies on the deposition of silica on the back surface of the substrate and a second one relies on the deposition of a chromium sublayer. Advantages and drawbacks of each of these techniques are presented.

Accurate analysis of mechanical stress in dielectric multilayers.

We present a systematic study of a stress coefficient of dielectric materials (SiO2, Nb2O5, and HfO2). In particular, we show a thickness dependence of the stress coefficient on layer thickness, which shows that the determination of this coefficient is complex and requires careful analysis. We then apply the different models of the stress coefficient to multilayer structures and show that stress-induced deformation can be precisely predicted in final components with a few percent accuracy.

Micromirrors with controlled amplitude and phase.

This paper describes the fabrication of circular micromirrors with diameters between 50 and 150 µm with controlled amplitude and phase. Design, manufacturing, and characterization method are presented.

All-Dielectric Silicon Nanogap Antennas To Enhance the Fluorescence of Single Molecules.

Plasmonic antennas have a profound impact on nanophotonics as they provide efficient means to manipulate light and enhance light-matter interactions at the nanoscale. However, the large absorption losses found in metals can severely limit the plasmonic applications in the visible spectral range. Here, we demonstrate the effectiveness of an alternative approach using all-dielectric nanoantennas based on silicon dimers to enhance the fluorescence detection of single molecules. The silicon antenna design is optimized to confine the near-field intensity in the 20 nm nanogap and reach a 270-fold fluorescence enhancement in a nanoscale volume of λ(3)/1800 with dielectric materials only. Our conclusions are assessed by combining polarization resolved optical spectroscopy of individual antennas, scanning electron microscopy, numerical simulations, fluorescence lifetime measurements, fluorescence burst analysis, and fluorescence correlation spectroscopy. This work demonstrates that all-silicon nanoantennas are a valid alternative to plasmonic devices for enhanced single molecule fluorescence sensing, with the additional key advantages of reduced nonradiative quenching, negligible heat generation, cost-efficiency, and complementary metal-oxide-semiconductor (CMOS) compatibility.

Advanced optical interference filters based on metal and dielectric layers.

In this paper, we investigate the design and the fabrication of an advanced optical interference filter based on metal and dielectric layers. This filter respects the specifications of the 2016 OIC manufacturing problem contest. We study and present all the challenges and solutions that allowed achieving a low deviation between the fabricated prototype and the target.

Broadband spectral transmittance measurements of complex thin-film filters with optical densities of up to 12.

A new transmittance measurement setup, based on the use of a tunable laser source and a low-noise scientific-grade CCD camera operating in perfect integration mode, is proposed to achieve the spectrally resolved characterization of thin-film filters with optical densities from 0 to 12 in a wavelength range between 400 and 1000 nm. The first experimental results obtained on dedicated components demonstrate the efficiency of this new measurement scheme.

Versatile Multilayer Metamaterial Nanoparticles with Tailored Optical Constants for Force and Torque Transduction.

The ability to apply force and torque directly to micro- and nanoscale particles in optical traps has a wide range of applications. While full control of both force and torque in three dimensions has been realized using top-down fabrication of rod-shaped particles composed of birefringent crystalline materials, widespread usage of such particles is limited as the optical constants of the predominant birefringent materials (quartz SiO2 and rutile TiO2) preclude coverage of the full application space of optical trapping. Here, we show that multilayer metamaterial nanoparticles provide access to a wide range of optical constants that can be specifically tuned for each application. Selecting the material pair Nb2O5/SiO2 from the library of amorphous dielectrics as our metamaterial, we show that its refractive index and birefringence can be designed by adapting the ratio of layer thicknesses. Using a robust top-down fabrication process, we show that uniformly sized, free-floating Nb2O5/SiO2 particles with high birefringence at moderate refractive index are obtained at high yield. Using an optical torque wrench, we show that these particles function as joint force and torque transducers while maintaining excellent stability in aqueous solutions and can be controllably optimized for particular physical characteristics such as maximal torque transfer or rapid response time. We expect that such customizable birefringent metamaterial nanoparticles whose properties surpass those of conventional crystalline particles will provide a means to unleash the full potential of optical trapping applications.