At the end of the 1970s, it was confirmed that dielectric multilayers can sustain Bloch surface waves (BSWs). However, BSWs were not widely studied until more recently. Taking advantage of their high-quality factor, sensing applications have focused on BSWs. Thus far, no work has been performed to manipulate and control the natural surface propagations in terms of defined functions with two-dimensional (2D) components, targeting the realization of a 2D system. In this study, we demonstrate that 2D photonic components can be implemented by coating an in-plane shaped ultrathin ( l/15) polymer layer on the dielectric multilayer. The presence of the polymer modifies the local effective refractive index, enabling direct manipulation of the BSW. By locally shaping the geometries of the 2D components, the BSW can be deflected, diffracted, focused and coupled with 2D freedom. Enabling BSW manipulation in 2D, the dielectric multilayer can play a new role as a robust platform for 2D optics, which can pave the way for integration in photonic chips. Multiheterodyne near-field measurements are used to study light propagation through micro-and nano-optical components. We demonstrate that a lens-shaped polymer layer can be considered as a 2D component based on the agreement between near-field measurements and theoretical calculations. Both the focal shift and the resolution of a 2D BSW lens are measured for the first time. The proposed platform enables the design of 2D all-optical integrated systems, which have numerous potential applications, including molecular sensing and photonic circuits. Keywords: Bloch surface wave; 2D optics; manipulation; micro-and nano-optics; nanophotonics; platform INTRODUCTION One or several elements are considered to comprise a two-dimensional (2D) optical system if they fulfill two conditions. First, the in-plane light propagation must have two spatial non-imaginary propagation constants. Second, the corresponding optical elements should have a 2D degree of freedom in shape. The previous statements may appear to imply that the reduction from three-dimensional (3D) to 2D is primarily a reduction in the degree of freedom. However, one of the main advantages is that 2D elements can have arbitrary shapes, which is difficult to achieve in 3D.There are various methods for addressing a 2D optical environment. One approach is represented by the use of wave-guiding media wherein the light is confined and propagated in a sandwiched structure. However, in the case of slab waveguides, the light is almost completely buried in the inner layers of the waveguide; thus, direct spatial mapping remains difficult or impossible. As an alternative to waveguides, a second route for 2D optics is represented by surface plasmons (SPPs) on smooth planar or structured metallic films. SPPs are electronic-electromagnetic modes sustained at an appropriate metallic/dielectric interface wherein the field reaches its maximum intensity at the surface of the metal.
A germanium (Ge) strip waveguide on a silicon (Si) substrate is integrated with a microfluidic chip to detect cocaine in tetrachloroethylene (PCE) solutions. In the evanescent field of the waveguide, cocaine absorbs the light near 5.8 mm, which is emitted from a quantum cascade laser. This device is ideal for (bio-)chemical sensing applications.
The frequency noise properties of commercial distributed feedback quantum cascade lasers emitting in the 4.6 μm range and operated in cw mode near room temperature (277 K) are presented. The measured frequency noise power spectral density reveals a flicker noise dropping down to the very low level of <100 Hz(2)/Hz at 10 MHz Fourier frequency and is globally a factor of 100 lower than data recently reported for a similar laser operated at cryogenic temperature. This makes our laser a good candidate for the realization of a mid-IR ultranarrow linewidth reference.
We report a prototype CO 2 gas sensor based on a simple blackbody infrared source and a spectrally narrow quantum cascade detector (QCD). The detector absorption spectrum is centered at 2260 cm −1 (4.4 μm) and has a full width at half maximum of 200 cm −1 (25 meV). It covers strong absorption bands of two spectrally overlapping CO 2 isotopomers, namely the P-branch of 12 CO 2 and the R-branch of 13 CO 2 . Acquisition of the spectral information and data treatment were performed in a Fourier transform infrared (FTIR) spectrometer. By flushing its sample compartment either with nitrogen, dry fresh air, ambient air, or human breath, we were able to determine CO 2 concentrations corresponding to the different gas mixtures. A detection limit of 500 ppb was obtained in these experiments.
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