We analyze how a probing particle modifies the infrared electromagnetic near field of a sample. The particle, described by electric and magnetic polarizabilities, represents the tip of an apertureless scanning optical near-field microscope (SNOM). We show that the interaction with the sample can be accounted for by ascribing to the particle dressed polarizabilities that combine the effects of image dipoles with retardation. When calculated from these polarizabilities, the SNOM signal depends only on the fields without the perturbing tip. If the studied surface is not illuminated by an external source but heated instead, the signal is closely related to the projected electromagnetic local density of states (EM-LDOS). Our calculations provide the link between the measured far-field spectra and the sample's optical properties. We also analyze the case where the probing particle is hotter than the sample and evaluate the impact of the dressed polarizabilities on near-field radiative heat transfer. We show that such a heated probe above a surface performs a surface spectroscopy, in the sense that the spectrum of the heat current is closely related to the local electromagnetic density of states. The calculations agree well with available experimental data.

We report local spectra of the near-field thermal emission recorded by a Fourier transform infrared spectrometer, using a tungsten tip as a local scatterer coupling the near-field thermal emission to the far field. Spectra recorded on silicon carbide and silicon dioxide exhibit temporal coherence due to thermally excited surface waves. Finally, we evaluate the ability of this spectroscopy to probe the frequency dependence of the electromagnetic local density of states.

Surface-plasmon polaritons (SPPs) are electromagnetic waves which are bound at a metal/dielectric interface. SPPs dispersion relation allows bent propagation and can lead to sub-wavelength energy concentration. These properties, well known in the visible and near-infrared, are lost at mid-infrared and THz wavelengths. Here we demonstrate an integrated device which is able to recover and exploit the confinement properties of SPPs. It operates in the mid-infrared wavelengths by electrical injection, It generates plasmonic excitations whose dispersion is artificially tailored via proper patterning of a purely metallic surface. We illustrate the power of this approach by demonstrating bending, focusing and sub-wavelength energy concentration. We demonstrate a compact (<0.1 mm2) device, which is electrically driven and is able to generate, couple, propagate on a chip over macroscopic distances, and focus mid infrared radiation into a subwavelength region.

We demonstrate a compact integrated device, electrically driven, which is able to recover and exploit the confinement properties of SPPs at long wavelengths. It operates in the mid-infrared by electrical injection, It generates plasmonic excitations whose dispersion is artificially tailored via proper patterning of a purely metallic surface. We illustrate the power of this approach by demonstrating bending, focusing and sub-wavelength energy concentration.

We analyse how a probing particle modifies infrared electromagnetic near fields. The particle, assimilated to both electric and magnetic dipoles, represents the tip of an apertureless scanning optical near-field microscope (SNOM). We show that the interaction can be accounted for by ascribing to the particle effective dipole polarizabilities that add the effect of retardation to the one of the image dipole. Apart from these polarizabilities, the SNOM signal expression depends only on the fields without tip perturbation, shown to be closely related to the electromagnetic density of states (EM-LDOS) and essentially linked to the sample's optical properties, so that measuring local spectra of heated samples is equivalent to performing a local surface spectroscopy. We also analyse the case where the probing particle is hotter. We evaluate in this case the impact of the effective polarizabilities on the tip-sample near-field radiative heat transfer. We also show that such an heated probe above a surface also performs a surface spectroscopy. The calculations agree well with available experimental data.

While freely propagating photons cannot be focused below their diffraction limit, surface-plasmon polaritons follow the metallic surface to which they are bound, and can lead to extremely sub-wavelength energy volumes. These properties are lost at long mid-infrared and THz wavelengths where metals behave as quasi-perfect conductors, but can in principle be recovered by artificially tailoring the surface-plasmon dispersion. We demonstrate - in the important mid-infrared range of the electromagnetic spectrum - the generation onto a semiconductor chip of plasmonic excitations which can travel along long distances, on bent paths, to be finally focused into a sub-wavelength volume. The demonstration of these advanced functionalities is supported by full near-field characterizations of the electromagnetic field distribution on the surface of the active plasmonic device.

A surface plasmon polariton (SPP) mode is directly excited on a metal/air interface using an integrated mid-infrared (MIR) quantum cascade laser. We demonstrate the SPP generation and propagation via far-field and near-field MIR imaging. We also demonstrate bending and focusing of MIR surface-plasmons using a sub-wavelength metal patterning.

Scattering-type near-field optical microscopy (sNSOM) allows one to map the propagation of purely evanescent waves such as surface plasmons polaritons (SPPs). We have recently used it to image SPPs generated electrically at the surface of a mid-infrared (MIR) quantum cascade laser (QCL) including all the building blocks for an integrated active plasmonic device. This talk will report on sNSOM observations on our new generation of integrated active plasmonic devices operating in the MIR, in which SPPs are launched on a metallic waveguide at distances of several hundred of micrometers from the end facet of a QCL.

We present a basic building block for the realization of integrated active plasmonic devices: a distributed-feedback semiconductor laser working at room temperature and λ=1.3μm obtained with metal patterning on a thinned top cladding.

We report a fast imaging method based on full field heterodyne interferometry for the purpose of frequency resolved temperature imaging. An integrated circuit is supplied with a modulated current resulting into a temperature modulation. The frequency content for this modulation is detected using an object beam and a reference beam, frequency-shifted to create a beating of the interference pattern. We obtain frequency domain spectra of the temperature with excellent precision.

We demonstrate a compact device for surface plasmon polariton (SPP) generation. A SPP mode is directly excited on a metal/air interface using a mid-infrared quantum cascade laser (QCL) with a dry etched facet. We demonstrate the SSP generation and propagation via mid-infrared imaging, using a metallic diffraction grating and a micro bolometer imaging camera to probe the SPP propagation. We also use an aperture-less near-field scanning microscope (a-SNOM) to directly observe the generated SPP.

We demonstrate a compact semiconductor laser device for generation and launching of surface plasmon into a passive waveguide at room temperature. Surface-plasmons are generated electrically at a single frequency using a distributed-feedback quantum cascade laser in the mid-infrared wavelengths, they are then launched in a passive metal strip and detected using an aperture-less near field scanning optical microscope.

Surface-plasmon polaritons (SPPs) are propagating electromagnetic modes bound at a metal-dielectric interface. We report on electrical generation of SPPs by reproducing the analogue in the near field of the slit-doublet experiment, in a device which includes all the building blocks required for a fully integrated plasmonic active source: an electrical generator of SPPs, a coupler, and a passive metallic waveguide. SPPs are generated upon injection of electrical current, and they are then launched at the edges of a passive metallic strip. The interference fringes arising from the plasmonic standing wave on the surface of the metallic strip are unambiguously detected with apertureless near-field scanning optical microscopy.

We demonstrate a compact, integrated device in which surface plasmon polaritons (SPPs) are injected into a passive metal waveguide. We directly excite a SPP mode at a metal-air interface using a room-temperature midinfrared quantum cascade laser which is integrated onto the microchip. The SPP generation relies on end-fire coupling and is demonstrated via both far-field and near-field imaging techniques in the midinfrared. On one hand, a metallic diffraction grating is used to scatter in the far-field a portion of the propagating SPPs, thus allowing their detection with a microbolometer camera. On the other hand, direct images of the generated SPPs in the near-field were collected with a scanning optical microscope.