The field of infrared (IR) photonics is currently undergoing remarkable progress, moving rapidly towards practical sensing applications demanded by medical therapy and diagnostics (theranostics). The Developments can be divided into three main categories: (i) novel devices and measurement concepts including advanced updates of classical approaches that push medical sensing into the spotlight; (ii) new demonstrations of photonic integrated circuit (PIC-)based IR devices enabling highly miniaturized sensors for point-of-care application as well as medical and wellness wearables; and (iii) technologically-mature IR demonstrators that enable first medical sensing and treatment applications. This roadmap paper provides a consolidated overview of this highly dynamic and interdisciplinary research field with a focus on the major roadblocks that limit the widespread adoption of IR photonics in large-scale medical diagnostics. Special attention is given to the ambivalence between the molecular-level spectroscopic interpretation and a broader health-state assessment, highlighting the need for a common framework. Additionally, the paper discusses the critical importance of unified measurement standards, calibration protocols, and medical certification processes to ensure the validity of experimental results, reproducibility, and clinical trust, particularly when novel experimental techniques and AI algorithms are involved. Perspectives from major past and current contributors to application-oriented IR photonics will be provided.

A long-standing challenge in ultrafast magnetism and functional materials research, in general, has been the generation of a universal, ultrafast stimulus able to switch between stable magnetic states. Solving this problem would open up many new opportunities for fundamental studies, potentially impacting future data storage technologies. Ideally, step-like magnetic field transients with infinitely fast rise time would serve this purpose. Here we develop a new approach to generate ultrafast magnetic field steps by quenching supercurrents in a superconductor. We achieve magnetic field steps with millitesla amplitude, picosecond rise times and slew rates approaching 1 GT s-1. We test the potential of this technique by coherently rotating the magnetization in a ferrimagnet. Although in the current geometry, the magnetic field step is not sufficient to achieve complete switching, suitable improvements in the device geometry could make these magnetic steps both larger and faster. We foresee new applications ranging from quenches across phase transitions to complete switching of magnetic order parameters.

Fourier-transform infrared spectroscopy (FTIR) has matured into a versatile technique with relevance for environmental monitoring, pharmaceutical research, and food safety applications. However, compared to other spectroscopic methods, it experiences slower progress in terms of power optimization, miniaturization, and adoption by industry. To overcome this limitation, we developed an ultra-broadband room-temperature FTIR instrument relying on commercially available components that offers a spectral coverage from 1.6 mu m to 31 mu m (9.7-190 THz) without changing optics at a single-watt-level of electrical power consumption. To demonstrate the capabilities of the instrument, we measured atmospheric species in multiple spectral regions with better than 1.5 cm-1 resolution.

In response to single-cycle THz pulses, we measured the linearity parameter of lithium tantalate pyroelectric detectors, over nearly three orders of magnitude in pulse energy, up to 2 mu J. The response was linear up to 1 mu J pulse energy and 25 mu J/cm(2) energy flux, and sublinear at higher irradiations. This finding shows the importance of characterizing the detector response linearity for accurate THz metrology. The detectors had high sensitivity in single-pulse detection mode up to 10 kHz repetition rate.

Using a lithium tantalate (LiTaO3) pyroelectric detector and a thermal incoherent source we demonstrate broadband room-temperature Fourier transform spectrometry from the near-infrared to THz range without changing optics. Atmospheric species are measured with GHz resolution.

FTIR spectroscopy holds significant untapped potential for materials analysis and laser characterization, but new developments are limited by the availability of simple, universal, and scalable components. Addressing this challenge, pyroelectric receivers PR No1 IR and PR No2 IR, and detectors ALUT3151 with sub-pixel binning and Diff ALUT3151 with additional true differential output have been developed. All models are based on thin LiTaO3, cover a wide wavelength range, do not require cooling, and operate at high Detectivity (D*) in the kHz range while being rugged and linear over four orders of IR flux magnitude. In this paper, we will focus on recent results towards a people´s-FTIR with reduced TTWS (Time Towards Working Setup). Besides the detector, the thermal source and the beamsplitter have been identified as critical components.

Coherent optical driving in quantum solids is emerging as a research frontier, with many reports of interesting non-equilibrium quantum phases1-4 and transient photo-induced functional phenomena such as ferroelectricity5,6, magnetism7-10 and superconductivity11-14. In high-temperature cuprate superconductors, coherent driving of certain phonon modes has resulted in a transient state with superconducting-like optical properties, observed far above their transition temperature Tc and throughout the pseudogap phase15-18. However, questions remain on the microscopic nature of this transient state and how to distinguish it from a non-superconducting state with enhanced carrier mobility. For example, it is not known whether cuprates driven in this fashion exhibit Meissner diamagnetism. Here we examine the time-dependent magnetic field surrounding an optically driven YBa2Cu3O6.48 crystal by measuring Faraday rotation in a magneto-optic material placed in the vicinity of the sample. For a constant applied magnetic field and under the same driving conditions that result in superconducting-like optical properties15-18, a transient diamagnetic response was observed. This response is comparable in size with that expected in an equilibrium type II superconductor of similar shape and size with a volume susceptibility χv of order -0.3. This value is incompatible with a photo-induced increase in mobility without superconductivity. Rather, it underscores the notion of a pseudogap phase in which incipient superconducting correlations are enhanced or synchronized by the drive.

Attosecond science has demonstrated that electrons can be controlled on the sub-cycle time scale of an optical wave, paving the way toward optical frequency electronics. Using controlled few-cycle optical waveforms, the study of sub-cycle electron emission has enabled the generation of attosecond ultraviolet pulses and the control of attosecond currents inside of solids. However, these experiments rely on high-energy laser systems not suitable for integration with microcircuits. To move towards integrated optical frequency electronics, a system suitable for integration into microcircuits capable of generating detectable signals with low pulse energies is needed. While current from plasmonic nanoantenna emitters can be driven at optical frequencies, low charge yields have been a significant limitation. In this work we demonstrate that large-scale electrically-connected plasmonic nanoantenna networks, when driven in concert, enable a much higher charge yield sufficient for shot-to-shot carrier-envelope phase detection, which is a hallmark of the underlying sub-cycle processes. We use a tailored sub-2-cycle mid-infrared waveform of only tens of nanojoules of energy to drive in excess of 2000 carrier-envelope-phase-sensitive electrons from interconnected plasmonic nanoantenna arrays that we detect on a single-shot basis using conventional electronics. Our work shows that electronically integrated plasmonic nanoantennas are a viable approach to integrated optical frequency electronics. By engineering the nanoantennas to the particular use case, such as carrier-envelope phase detection, and optimizing the density and total amount, the output signals are fully controlled. This approach to optical frequency electronics will further enable many interesting applications, such as petahertz-bandwidth electric field sampling or the realization of logic gates operating at optical frequencies.

John Fleming demonstrated in 1905 the first vacuum diode based on thermionic electron emission for the rectification of AC electric fields and started an avalanche of developments in microwave electronics such as sensitive wireless receivers or signal amplifiers [1]. Around 100 years later, lasers connected the optical domain with the microwave domain by coherently locking optical frequencies to microwave frequencies with carrier-envelope (CE) offset stable frequency combs, enabling many applications such as precision metrology [2]. To directly drive electronic systems with optical frequencies, many approaches based on carrier-envelope phase (CEP) stable few-cycle NIR pulses, directly driving sub-cycle electron currents at optical frequencies in dielectrics, metal-vacuum-metal junctions, or gases have been investigated [3]–[6]. We present an approach based on the large-scale integration of metallic nanoantennas into conventional electronic readout circuitry; see Figs. 1 a and b. When irradiating an array of $\sim 1000$ antennae with 18 fs, CE-stable pulses having a center wavelength of 2640 nm, repetition rate of 50 kHz, and peak field strengths up to 1.7 Vnm −1 , we observe shot-to-shot changes in CE phase dependent charge amplitudes up to $\sim 3000 \ \mathrm{e}$ , see Fig. 1 c. We further investigated the CE sensitive charge amplitude as a function of field strength and found excellent agreement with models based on the quasi-static tunneling approximation extracting an effective field enhancement of 8 by the antenna structure, in very good agreement with our electromagnetic simulation; see Fig. 1 d.

We report single-shot detection of the carrier-envelope phase of few-cycle mid-infrared waveforms using petahertz electronic networks. Leveraging large-area networks, we demonstrate a charge amplitude of 2,500 electrons per shot, enabling the detection at the full laser repetition rate of 50 kHz.

We describe a mid-infrared pump - terahertz-probe setup based on a CO2 laser seeded with 10.6 μm wavelength pulses from an optical parametric amplifier, itself pumped by a Ti:Al2O3 laser. The output of the seeded CO2 laser produces high power pulses of nanosecond duration, which are synchronized to the femtosecond laser. These pulses can be tuned in pulse duration by slicing their front and back edges with semiconductor-plasma mirrors irradiated by replicas of the femtosecond seed laser pulses. Variable pulse lengths from 5 ps to 1.3 ns are achieved, and used in mid-infrared pump, terahertz-probe experiments with probe pulses generated and electro-optically sampled by the femtosecond laser.

The design of a velocity map imaging (VMI) spectrometer is presented with a novel gas capillary integrated into the repeller electrode. The capillary is made of semiconductive lead glass, which replicates the electrostatic field of the VMI lenses. Thus, the target gas can be directly supplied to the interaction zone without degrading the VMI resolution. With this design, a high gas density and a large free aperture to focus long wavelength radiation into the VMI spectrometer have been achieved, which facilitates time resolved experiments with intense terahertz (THz)-light fields. The performance of the VMI spectrometer is demonstrated with momentum maps of electrons from multiphoton ionization of xenon and a first extreme ultraviolet-THz-streak experiment.

Far and mid infrared optical pulses have been shown to induce non-equilibrium unconventional orders in complex materials, including photo-induced ferroelectricity in quantum paraelectrics, magnetic polarization in antiferromagnets and transient superconducting correlations in the normal state of cuprates and organic conductors. In the case of non-equilibrium superconductivity, femtosecond drives have generally resulted in electronic properties that disappear immediately after excitation, evidencing a state that lacks intrinsic rigidity. Here, we make use of a new optical device to drive metallic K_3C_60 with mid-infrared pulses of tunable duration, ranging between one picosecond and one nanosecond. The same superconducting-like optical properties observed over short time windows for femtosecond excitation are shown here to become metastable under sustained optical driving, with lifetimes in excess of ten nanoseconds. Direct electrical probing becomes possible at these timescales, yielding a vanishingly small resistance. Such a colossal positive photo-conductivity is highly unusual for a metal and, when taken together with the transient optical conductivities, it is rather suggestive of metastable light-induced superconductivity.

High power mid-infrared light pulses of tunable pulse length were generated to stabilize light-induced superconductivity in K 3 C 60 for nanoseconds. This metastable state showed a vanishing electrical resistance at five times the material’s equilibrium critical temperature.

We use resonant soft x-ray diffraction to track the photoinduced dynamics of the antiferromagnetic structure in a NdNiO3 thin film. Femtosecond laser pulses with a photon energy of 0.61 eV, resonant with electron transfer between long-bond and short-bond nickel sites, are used to excite the material and drive an ultrafast insulatormetal transition. Polarization-sensitive soft x-ray diffraction, resonant to the nickel L-3 edge, then probes the evolution of the underlying magnetic spiral as a function of time delay with 80 ps time resolution. By modeling the azimuthal dependence of the scattered intensity for different linear x-ray polarizations, we benchmark the changes of the local magnetic moments and the spin alignment. The measured changes are consistent with a reduction of the long-bond site magnetic moments and an alignment of the spins towards a more collinear structure at early time delays.

Angle resolved spectra of photoelectrons generated by multiphoton ionization in the presence of THz-light fields were measured. We observed a strong electron modulation for different THz phases, which we attribute to momentum transfers caused by rescattering at the ionic core.

Temendous developments of novel ultrafast light sources based on High Harmonic Generation (HHG) or Free-Electron-Lasers (FELs) in the last decade have opened up new experimental regimes in the vacuum-ultraviolet (VUV), extreme-ultraviolet (XUV) down to X-ray spectral regions. Especially, the unique combination of coherent intense radiation with short pulse duration holds very promising perspectives for time-resolved molecular movies by obtaining information on molecular structure and function on atomic length scale with time resolution down to the attosecond domain. An understanding of the way how an intense X-ray light interacts with matter is of fundamental importance for studies of molecular structure and dynamics. Therefore this research topic is actively pursued by theoretical and experimental work within the photon science community. The main objective of the Extreme Light Infrastructure – ELI-Beamlines project – in Dolní Břežany near Prague, Czech Republic is to establish an international user facility for fundamental and applied research with advanced laser sources. The research group for applications in molecular, biomedical, and material sciences works on the development of experimental capabilities using secondary sources that are driven by the unique ELI-Beamlines lasers. A central activity is the development of the multi-purpose user end-station (MAC) for experiments in atomic, molecular, and optical sciences and coherent diffractive imaging. The MAC user end-station is equipped with electron/ion time-of-flight spectrometers, Velocity Map Imaging detector, a detector for coherent diffractive imaging and state-of-the-art sample delivery systems to enable advanced photon science experiments on low density targets (atoms, molecules, clusters, nanometer size single intact free of substrate organic and inorganic particles and crystals, vacuum compatible tens of nanometers to a few micrometers thick liquid sheets formed with gas and by colliding jets technique, cylindrical GDVN jets and aerosols) in a broad range of the electromagnetic spectrum from THz to (soft) X-rays. The THz-field driven streaking is a novel experimental technique to study the electronic response of many-electron systems to irradiation with intense ultra-short (soft) X-rays pulses [1]. The effect of lightfield streaking can be understood as an additional momentum acquired by the free electrons in the presence of a dressing electric field [2]. By changing the time-delay between the ionizing XUV pulse with respect to the streaking field and measuring the electron kinetic energy spectra, a streaking spectrogram is obtained. In the streaking experiment half of the oscillation period of the streaking field has to be shorter than the temporal width of the electron distribution [2]. Therefore, to resolve the electron dynamics that is initiated by the femtosecond (soft) X-ray pulse, a THz-field is used [1].

We demonstrate the generation of narrowband (<1 THz) high-energy (~2 uJ) carrier-envelope phase-stable pulses, tunable between 4 and 18 THz as achieved by difference-frequency mixing between chirped near-infrared pulses in organic DSTMS.

Molecular wave-packet dynamics in oxygen are studied in the time domain, using a single-color VUV-pump-VUV-probe scheme. 17-fs VUV pulses, centered at 161 nm are generated via high-order harmonic generation driven by an intense 800-nm pulse leading to VUV pulse energies that reach 1.1 mu J per pulse. An all-reflective interferometric pump-probe scheme is used for studying the delay dependence of the molecular oxygen ion signal with simultaneous nonresonant photoionization of krypton as a precise timing-reference. Access to the excited dissociative state lifetime is provided by the resulting delay-dependent O-2(+) signal, ultimately limited by the molecular ionization window. The ability to use a two-photon VUV probe provides the delay-dependent detection of O+ as an additional observable, extending the dissociation observation window.