East China Normal University（华东师范大学）；Chongqing Institute of East China Normal University（华东理工大学重庆研究院）；Shanxi University（山西大学）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）；Guangyang Bay Laboratory（广阳湾实验室）
High-order edge-enhanced imaging enables precise feature localization and effective background suppression, offering a powerful tool for real-time recognition and high-contrast visualization. Extending this capability to the mid-infrared (MIR) regime is particularly valuable for applications such as biomedical diagnostics, material inspection, and remote sensing, yet remains limited by inadequate spatial-frequency modulation fidelity and low detection sensitivity. Here, we demonstrate a high-sensitivity MIR upconversion differentiator operating at 3 $μ$m, which achieves isotropic high-order edge enhancement by optically imprinting topological complex-amplitude patterns onto MIR Fourier components via nonlinear parametric interaction. Vortex transfer functions $t(k_r, ϕ) \propto k_r^\ell e^{i\ellϕ}$ are precisely encoded on a phase-only spatial light modulator to enable tunable MIR differentiation from first- to fourth- order, with real-time switching at up to 60 Hz. Benefiting from a low-noise upconversion process and a single-photon-sensitive silicon camera, the system achieves high-contrast edge imaging under low-light conditions. Experimental results confirm accurate edge extraction and background suppression for both amplitude and phase objects, hence underscoring its potential for noninvasive diagnostics and label-free material analysis.
A fully stabilized mid-infrared optical frequency comb spanning from 2.9 to 3.4 um is described. The comb is based on half-harmonic generation in a femtosecond optical parametric oscillator, which transfers the high phase coherence of a fully stabilized near-infrared Er-doped fiber laser comb to the mid-infrared region. The method is simple, as no phase-locked loops or reference lasers are needed. Precise locking of optical frequencies of the mid-infrared comb to the pump comb is experimentally verified at sub-20 mHz level, which corresponds to a fractional statistical uncertainty of 2x10-16 a…
In this study, rigorous numerical calculation was utilized to characterize the focal properties of mid-infrared silicon microlens with the size about tens of micrometers. It is found that the focal shift phenomenon also exists in mid-infrared regime, which behaves differently from that of visual and near-infrared wavelength. Focal properties of silicon microlens were also measured experimentally, showing well coherence with simulation results. Our results provide systemic understanding of focal shift in mid-infrared regime, at that wavelength special consideration should be paid in micro-nano …
We demonstrate efficient generation of mid-infrared frequency combs based on continuous-wave-seeded femtosecond optical parametric generation in nonlinear waveguides. Conversion of the near-infrared pump to signal and idler light takes place with very high efficiency (74 %) and the threshold (25 pJ) is over 300 times lower than in bulk analogs. Relative intensity noise of the mid-infrared comb is exceptionally low, below 5*10-5 (detector-limited, integrated from 10 Hz to 2 MHz). Furthermore, the mid-infrared bandwidth can be increased by driving the process with broadband pump obtained via sup…
With growing interest in the mid-infrared spectral region, dysprosium has recently been revisited for efficient high-performance infrared source development. Despite historically receiving less attention than other rare earth ions, in recent years lasers utilizing the dysprosium ion as the laser material have set record mid-infrared performance, including tunability from 2.8 to 3.4 um (in addition to 4.3 um lasing), continuous wave powers exceeding 10 W, greater than 73% slope efficiencies, and even ultrafast pulsed operation. Herein, the unique energy level structure and spectroscopy of the d…
We report on the generation of nanosecond mid-infrared pulses having frequency tunability, a narrow linewidth, and a high pulse energy. These pulses are obtained by frequency mixing between injection-seeded near-infrared pulses in potassium titanyl arsenate crystals. A continuous-wave external cavity laser diode or a Ti:sapphire ring laser is used as a tunable seeding source for the near-infrared pulses. The typical energy of the generated mid-infrared pulses is in the range of 0.4-1 mJ/pulse. The tuning wavelength ranges from 3142 to 4806 nm. A narrow linewidth of 1.4 GHz and good frequency r…
Strong mid-infrared light-matter interaction has attracted extensive attention as it opens up new frontiers in nonlinear optics. Here we observe through simulations a novel aspect of mid-infrared pulse dynamics in a high-pressure gas-filled capillary, where a pulse with a power well below the critical power for Kerr self-focusing undergoes an astonishing rise of the peak intensity following an extremely efficient spectral broadening. This intensity enhancement is attributed to the Kerr-induced focusing of the supercontinuum. Our study provides an interesting perspective for controlling the las…
We measure the nonlinear refractive index coefficients in N$_2$, O$_2$ and Ar from visible through mid-infrared wavelengths (λ= 0.4 - 2.4 μm). The wavelengths investigated correspond to transparency windows in the atmosphere. Good agreement is found with theoretical models of $χ^{(3)}$. Our results are essential for accurately simulating the propagation of ultrashort mid-IR pulses in the atmosphere.
We report evidence of beam cleanup during stimulated Raman scattering in silicon. An amplified near-diffraction-limited Stokes beam is obtained from a severely aberrated pump beam.
We demonstrate for the first time a mid infrared silicon Raman amplifier. Amplification of 12 dB is reported for a signal at 3.39 micron wavelength. The active medium was a 2.5 cm long silicon sample that was pumped with 5ns pulses at 2.88 micron. The absence of the nonlinear losses which severely limit the performance of silicon Raman devices in the near infrared combined with unsurpassed crystal quality, high thermal conductivity render silicon a very attractive Raman medium. Such a technology can potentially extend silicon photonics application beyond data communication in the near infrared…
We demonstrate non-degenerate photon-pair generation by spontaneous parametric down conversion in a silver gallium sulfide AgGaS$_2$ crystal. By tuning the pump wavelength, we achieve phase matching over a large spectral range. This allows to generate idler photons in the mid-infrared spectral range above 6 $μm$ wavelength with corresponding signal photons in the visible. Also, we show photon pair generation with broad spectral bandwidth. These results are a valuable step towards the development of quantum imaging and sensing techniques in the mid-infrared.
For the first time, we demonstrated that a hyper-broadband from 2μm to 10μm can be generated with a high spectral flatness by using a ~4 um pump and an As2Se3 photonic crystal fiber. The broad and flat dispersion profile and the low guiding loss of the endlessly single-mode As2Se3 photonic crystal fibers combining with the high nonlinearity and wide mid-infrared transparent window of As2Se3 chalcogenide glass are essential for this high performance mid-infrared laser source.
Besides being the foundational material for microelectronics, in optics, crystalline silicon has long been used for making infrared lenses and mirrors. More recently, silicon has become the key material to achieve large-scale integration of photonic devices for optical interconnect and telecommunication. For optics, silicon has significant advantages: it offers a very high refractive index and is highly transparent in the spectral range from 1.2 to 8 micron. To fully exploit silicon's superior performance in a remarkably broad range and to enable new optoelectronic functionalities, here we des…
Silicon photonics has recently been proposed for a diverse set of applications at mid-infrared wavelengths, the implementation of which require on-chip photodetectors. In planar geometries, dopant-based extrinsic photoconductors have long been used for mid-infrared detection with Si and Ge acting as host materials. Leveraging the dopant-induced sub-bandgap trap-states used in bulk photoconductors for waveguide integrated mid-infrared detectors offers simple processing, integration, and operation throughout the mid-infrared by appropriate choice of dopant. In particular, Si doped with Zn forms …
We report a singly resonant continuous-wave optical parametric oscillator (SRO), which is pumped by a semiconductor laser system and operates in the mid-infrared region (2.9 to 3.6 μm). Fast tuning of the mid-infrared output wavelength by more than 200 nm is demonstrated by scanning the pump laser wavelength through only 1.25 nm, without any need to adjust the SRO settings. The exceptionally large tuning range is obtained by choosing a pump wavelength (780 nm) that corresponds to a turning point of the group velocity mismatch between the phase-matched signal and idler waves of the SRO.
Wavelength stability of free-electron lasers (FELs) is one of the important parameters for various applications. In this paper we describe two different methods to diagnose the wavelength stability of a mid-infrared (MIR) FEL. The first one is based on autocorrelation which is usually used to measure the pulse duration, and the second one is based on frequency upconversion through sum-frequency mixing (SFM).
We report on a high-power mid-infrared frequency comb source based on a femtosecond Er:fiber oscillator with a stabilized repetition rate at 250 MHz. The mid-infrared frequency comb is produced through difference frequency generation in a periodically poled MgO-doped lithium niobate crystal. The output power is about 120 mW with a pulse duration of about 80 fs, and spectrum coverage from 2.9 to 3.6 um. The coherence properties of the produced high-power broadband mid-infrared frequency comb are maintained, which was verified by heterodyne measurements. As the first application, the spectrum of…
We report the observation of modulation instability in the mid-infrared spectral region by pumping a hybrid polymer-chalcogenide optical microwire with a femtosecond optical parametric oscillator operating at 2.6 μm. It is further shown that this modulation instability occurs in the normal dispersion regime through negative fourth-order dispersion and leads to far detuned parametric frequency conversion at 2 μm and 3.5 μm, despite the presence of a strong absorption band around 2.8 μm. Stochastic nonlinear Schrödinger equation simulations of mid-infrared modulation instability are in excellent…
Light emitted from single-mode semiconductor lasers generally has large divergence angles, and high numerical aperture lenses are required for beam collimation. Visible and near infrared lasers are collimated using aspheric glass or plastic lenses, yet collimation of mid-infrared quantum cascade lasers typically requires more costly aspheric lenses made of germanium, chalcogenide compounds, or other infrared-transparent materials. Here we report mid-infrared dielectric metasurface flat lenses that efficiently collimate the output beam of single-mode quantum cascade lasers. The metasurface lens…
Simulation results, fabrication details and measurements are presented for a one dimensional aperture and grating array for the purpose of plasmonic beam shaping of the λ=3.99μm output of an optically pumped semiconductor laser.
Mid- and long-wavelength infrared computational ghost spectroscopy
Sichuan University（四川大学）；University of Electronic Science & Technology of China（电子科技大学）；Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Science（中国科学院上海光学精密机械研究所）；Tampere University（坦佩雷大学）
We report on the spatially resolved full amplitude and phase characterization of mid-infrared high intensity laser pulses generated in a three stage OPA. We use a spatially-encoded arrangement (SEA-)SPIDER with spectral filters for ancilla generation for spatially resolved characterization. Using five interchangeable filter sets we are able to characterize pulses from 1 to 2μm with one single device with minimal adjustments.
We explore broadband, wide-angle mid-infrared rectification based on nanopatterned hyperbolic metamaterials (HMM), composed of two dissimilar metals separated by a sub-nanometer tunnel barrier. The exotic slow-light modes supported by such periodically trenched HMMs efficiently trap incident radiation in massively parallel metal-insulator-metal tunnel junctions supporting ultrafast optical rectification induced by photon-assisted tunneling. This leads to highly efficient photon-to-electron conversion, orders of magnitude larger than conventional rectennas. Our results promise an impact on infr…
We experimentally demonstrate in a difference-frequency generation mid-infrared frequency comb source the effect of temporal overlap between pump- and signal- pulse to the relative intensity noise (RIN) of the idler pulse. When scanning the temporal delay between our 130 fs long signal- and pump pulses, we observe a RIN minimum with a 3 dB width of 20 fs delay and an RIN increase of 20 dB in 40 fs delay at the edges of this minimum. We also demonstrate active long-term stabilization of the mid-infrared frequency comb source to the temporal overlap setting corresponding to the lowest RIN operat…
Thin-film lithium niobate (TFLN) is an emerging platform for compact, low-power nonlinear-optical devices, and has been used extensively for near-infrared frequency conversion. Recent work has extended these devices to mid-infrared wavelengths, where broadly tunable sources may be used for chemical sensing. To this end, we demonstrate efficient and broadband difference frequency generation between a fixed 1-micron pump and a tunable telecom source in uniformly-poled TFLN-on-sapphire by harnessing the dispersion-engineering available in tightly-confining waveguides. We show a simultaneous 1-2 o…
We report a silica glass nested capillary anti-resonant nodeless fiber with transmission and low bending sensitivity in the mid-infrared around 4000 nm. The fiber is characterized in terms of transmission over 1700-4200 nm wavelengths, revealing a mid-infrared 3500-4200 nm transmission window, clearly observable for a 12 m long fiber. Bending loss around 4000 nm is 0.5 dB/m measured over 3 full turns with 40 mm radius, going up to 5 dB/m for full turns with 15 mm radius. Our results provide experimental evidence of hollow-core silica fibers in which nested, anti-resonant capillaries provide hi…
Mid-infrared dual-comb spectroscopy has the potential to supplant conventional high-resolution Fourier transform spectroscopy in applications that require high resolution, accuracy, signal-to-noise ratio, and speed. Until now, dual-comb spectroscopy in the mid-infrared has been limited to narrow optical bandwidths or to low signal-to-noise ratios. Using a combination of digital signal processing and broadband frequency conversion in waveguides, we demonstrate a mid-infrared dual-comb spectrometer that can measure comb-tooth resolved spectra across an octave of bandwidth in the mid-infrared fro…
Graphene plasmonic nanostructures enable subwavelength confinement of electromagnetic energy from the mid-infrared down to the terahertz frequencies. By exploiting the spectrally varying light scattering phase at vicinity of the resonant frequency of the plasmonic nanostructure, it is possible to control the angle of reflection of an incoming light beam. We demonstrate, through full-wave electromagnetic simulations based on Maxwell equations, the electrical control of the angle of reflection of a mid-infrared light beam by using an aperiodic array of graphene nanoribbons, whose widths are engi…
We demonstrate a new regime for mid-infrared optical parametric chirped pulse amplification (OPCPA) based on achromatic quasi-phase-matching. Our mid-infrared OPCPA system is based on collinear aperiodically poled lithium niobate (APPLN) pre-amplifiers and a non-collinear PPLN power amplifier. The idler output has a bandwidth of 800 nm centered at 3.4 $μ$m. After compression, we obtain a pulse duration of 44.2 fs and a pulse energy of 21.8 $μ$J at a repetition rate of 50 kHz. We explain the wide applicability of the non-collinear QPM amplification scheme we used, including how it can enable oc…
We experimentally demonstrate a wide band near perfect light absorber in the mid-wave infrared region using multiplexed plasmonic metal structures. The wide band near perfect light absorber is made of two different size gold metal squares multiplexed on a thin dielectric spacing layer on the top of a thick metal layer in each unit cell. We also fabricate regular non-multiplexed structure perfect light absorbers. The multiplexed structure IR absorber absorbs above 98% incident light over a much wider spectral band than the regular non-multiplexed structure perfect light absorbers in the mid-wav…
Filamentation of ultrashort laser pulses in the atmosphere offers unique opportunities for long-range transmission of high-power laser radiation and standoff detection. With the critical power of self-focusing scaling as the laser wavelength squared, the quest for longer-wavelength drivers, which would radically increase the peak power and, hence, the laser energy in a single filament, has been ongoing over two decades, during which time the available laser sources limited filamentation experiments in the atmosphere to the near-infrared and visible ranges. Here, we demonstrate filamentation of…
The newly-emergent two-dimensional topological insulators (TIs) have shown their unique electronic and optical properties, such as good thermal management, high nonlinear refraction index and ultrafast relaxation time. Their narrow energy band gaps predict their optical absorption ability further into the mid-infrared region and their possibility to be very broadband light modulators ranging from the visible to the mid-infrared region. In this paper, a mid-infrared mode-locked fluoride fiber laser with TI Bi2Te3 nano-sheets as the saturable absorber is presented. Continuous wave lasing, Q-swit…
We stabilize the idler frequency of a singly-resonant optical parametric oscillator directly to the resonance of a mid-infrared Fabry-Pérot reference cavity. This is accomplished by the Pound-Drever-Hall locking scheme, controlling either the pump laser or the resonant signal frequency. A residual relative frequency noise power spectral density below 10$^3$ Hz$^2$/Hz is reached, with a Gaussian linewidth of 920 Hz over 100 ms, which demonstrates the potential for reaching spectral purity down to the Hz level by locking the optical parametric oscillator against a mid-infrared cavity with state-…
We have demonstrated what we believe to be the first waveguide photonic crystal cavity operating in the mid-infrared. The devices were fabricated from Ge23Sb7S70 chalcogenide glass on CaF2 substrates by combing photolithographic patterning and focus ion beam milling. The waveguide-coupled cavities were characterized using a fiber end fire coupling method at 5.2 μm wavelength, and a loaded quality factor of ~ 2,000 was measured near the critical coupling regime.
We demonstrate thin-film metamaterials with resonances in the mid-infrared wavelength range. Our structures are numerically modeled and experimentally characterized by reflection and angularly-resolved thermal emission spectroscopy. We demonstrate strong and controllable absorption resonances across the mid-infrared wavelength range. In addition, the polarized thermal emission from these samples is shown to be highly selective and largely independent of emission angles from normal to 45 degrees. Experimental results are compared to numerical models with excellent agreement. Such structures hol…
We designed and simulated freestanding dielectric optical metasurfaces based on arrays of etched nanoholes in a silicon membrane. We showed $2π$ phase control and high forward transmission at mid-infrared wavelengths by tuning the dimensions of the holes. We also identified the mechanisms responsible for high forward scattering efficiency and showed that these conditions are connected with the well-known Kerker conditions already proposed for isolated scatterers. A beam deflector was designed and optimized through sequential particle swarm and gradient descent optimization to maximize transmis…
Mid-infrared femtosecond optical frequency combs were produced by difference frequency generation of the spectral components of a near-infrared comb in a 3-mm-long MgO:PPLN crystal. We observe strong pump depletion and 9.3 dB parametric gain in the 1.5 μm signal, which yields powers above 500 mW (3 μW/mode) in the idler with spectra covering 2.8 μm to 3.5 μm. Potential for broadband, high-resolution molecular spectroscopy is demonstrated by absorption spectra and interferograms obtained by heterodyning two combs.
We demonstrate a fibre-based approach that generates mid-infrared femtosecond pulses in the 3-4 μm spectral region with microjoule-level single pulse energy. This is realised in a piece of gas-filled antiresonant hollow-core fibre that is pumped by a two-micron light source. A rapid variation of the dispersion near a structural resonance of the fibre creates a phase-matching point in the mid-infrared, which mediates the frequency-down conversion. We generate femtosecond pulses centred at 3.16 μm wavelength with the pulse energy of more than 1 μJ, achieving the conversion efficiency as high as …
Mid-infrared optical frequency combs are of significant interest for molecular spectroscopy due to the large absorption of molecular vibrational modes on one hand, and the ability to implement superior comb-based spectroscopic modalities with increased speed, sensitivity and precision on the other hand. Substantial advances in mid-infrared frequency comb generation have been made in recent years based on nonlinear frequency conversion, microresonator Kerr frequency combs, quantum cascade lasers and mode locking regimes. Here we demonstrate a simple, yet effective method for the direct generati…
Mid-infrared (mid-IR) frequency combs have broad applications in molecular spectroscopy and chemical/biological sensing. Recently developed microresonator-based combs in this wavelength regime could enable portable and robust devices using a single-frequency pump field. Here, we report the first demonstration of a modelocked microresonator-based frequency comb in the mid-IR spanning 2.4 μm to 4.3 μm. We observe high pump-to-comb conversion efficiency, in which 40% of the pump power is converted to the output comb power. Utilizing an integrated PIN structure allows for tuning the silicon micror…
We demonstrate a multi-spectral polarization sensitive mid-infrared dots-in-a-well (DWELL) photodetector utilizing surface-plasmonic resonant elements, with tailorable frequency response and polarization selectivity. The resonant responsivity of the surface-plasmon detector shows an enhancement of up to 5 times that of an unpatterned control detector. As the plasmonic resonator involves only surface patterning of the top metal contact, this method is independent of light-absorbing material and can easily be integrated with current focal plane array processing for imaging applications.
We report on the mid-infrared nonlinear photothermal spectrum of the neat liquid crystal 4-Octyl-4'-Cyanobiphenyl (8CB) using a tunable Quantum Cascade Laser (QCL). The nonequilibrium steady state characterized by the nonlinear photothermal infrared response undergoes a supercritical pitchfork bifurcation. The bifurcation, observed in heterodyne two-color pump-probe detection, leads to ultrasharp nonlinear infrared spectra similar to those reported in the visible region. A systematic study of the peak splitting as function of absorbed infrared power shows the bifurcation has a critical exponen…
We propose and design an ultra-compact and broadband tunable multimode interference (MMI) splitter in mid-infrared based on graphene plasmonic waveguides. The size of the device is only 0.56μm*1.2μm, which corresponds to device area of only about 0.014λ^2, where λ is the vacuum wavelength. And the center wavelength of the device can be tuned in a broad band from 7μm to 9μm with the Fermi level of graphene varied from 0.5eV to 1eV. Furthermore, the device is easy to be fabricated on chip.
We demonstrate the generation of nanosecond mid-infrared pulses via fast modulation of thermal emissivity, enabled by the absorption of visible pump pulses in unpatterned silicon and gallium arsenide. The free-carrier dynamics in these materials result in nanosecond-scale modulation of thermal emissivity, leading to nanosecond pulsed thermal emission. To our knowledge, the nanosecond thermal-emissivity modulation demonstrated in this work is three orders of magnitude faster than what has been previously demonstrated. We also indirectly observed sub-nanosecond thermal pulses from hot carriers i…
We report on Mid-infrared (MIR) OCT at 4 $μ$m based on collinear sum-frequency upconversion and promote the A-scan scan rate to 3 kHz. We demonstrate the increased imaging speed for two spectral realizations, one providing an axial resolution of 8.6 $μ$m, and one providing a record axial resolution of 5.8 $μ$m. Image performance is evaluated by sub-surface micro-mapping of a plastic glove and real-time monitoring of CO$_2$ in parallel with OCT imaging.
The quantum cascade laser (QCL) has evolved to be a compact, powerful source of coherent mid-infrared (mid-IR) light. However, its fast gain dynamics strongly restricts the formation of ultrashort pulses. As such, the shortest pulses reported so far were limited to a few picoseconds with some hundreds of milliwatts of peak power, strongly narrowing their applicability for time-resolved and nonlinear experiments. Here, we demonstrate an alternative approach capable of producing near-transform-limited sub-picosecond pulses with several watts of peak power. Starting from a frequency modulated pha…
The mid-infrared spectral range (2 to 20 μm) is of particular importance for chemistry, biology and physics as many molecules exhibit strong ro-vibrational fingerprints. Frequency combs - broad spectral bandwidth coherent light sources consisting of equally spaced sharp lines - are creating new opportunities for advanced spectroscopy. Mid-infrared frequency comb sources have recently emerged but are still facing technological challenges, like achieving high power per comb line and tens of GHz line spacing as required for e.g. direct comb spectroscopy. Here we demonstrate a novel approach to cr…
We demonstrate mid-infrared (mid-IR) supercontinuum generation (SCG) with instantaneous bandwidth from 2.2 to 5 μm at 40 dB below the peak, covering the wavelength range desirable for molecular spectroscopy and numerous other applications. The SCG occurs in a tapered As2S3 fiber prepared by in-situ tapering and is pumped by femtosecond pulses from the subharmonic of a mode-locked Er-doped fiber laser. Interference with a narrow linewidth c.w. laser verifies that the coherence properties of the near-IR frequency comb have been preserved through these cascaded nonlinear processes. With this appr…
Mid-infrared silicon photonics has recently emerged as a new technology for a wide range of applications such as optical communication, lidar, and bio-sensing. One key component enabling this technology is the mid-infrared optical modulator used for encoding optical signals. Here, we present a GeSn electro-absorption modulator that can operate in the mid-infrared range. Importantly, this device is monolithically integrated on a silicon substrate, which provides compatibility with standard complementary metal-oxide-semiconductor technology for scalable manufacturing. By alloying Ge with Sn to e…
Mid-infrared photothermal microscopy is a new chemical imaging technology in which a visible beam senses the photothermal effect induced by a pulsed infrared laser. This technology provides infrared spectroscopic information at sub-micron spatial resolution and enables infrared spectroscopy and imaging of living cells and organisms. Yet, current mid-infrared photothermal imaging sensitivity suffers from a weak dependance of scattering on temperature and the image quality is vulnerable to the speckles caused by scattering. Here, we present a novel version of mid-infrared photothermal microscopy…
Nonlinear interferometers allow for mid-infrared spectroscopy with near-infrared detection using correlated photons. Previous implementations have demonstrated a spectral resolution limited by spectrally selective detection. In our work, we demonstrate mid-infrared transmission spectroscopy in a nonlinear interferometer using single-pixel near-infrared detection and Fourier-transform analysis. A sub-wavenumber spectral resolution allows for rotational-line-resolving spectroscopy of gaseous samples in a spectral bandwidth of over 700$\,$cm$^{-1}$. We use methane transmission spectra around 3.3$…
We present here our recent progress in the three-dimensional (3D) direct laser writing (DLW) of step-index core waveguides inside diverse technologically relevant dielectric substrates, with specific emphasis on the demonstration of DLW mid-infrared waveguiding in the whole transparency range of these materials.
We experimentally investigate the generation of above-threshold harmonics completely from argon atoms on an excited state using mid-infrared femtosecond laser pulses. The highly nonlinear dependences of the observed signal on the pulse energy and polarization of the driver laser pulses indicate its non-perturbative characteristic.
This article reports the advances on the development of mid-infrared integrated optics for stellar interferometry. The devices are fabricated by laser writing techniques on chalcogenide glasses. Laboratory characterizaton is reported and analyzed.
Mid-infrared light scatters much less than shorter wavelengths, allowing greatly enhanced penetration depths for optical imaging techniques such as optical coherence tomography (OCT). However, both detection and broadband sources in the mid-IR are technologically challenging. Interfering entangled photons in a nonlinear interferometer enables sensing with undetected photons making mid-IR sources and detectors obsolete. Here we implement mid-infrared frequency-domain OCT based on ultra-broadband entangled photon pairs. We demonstrate 10 $μ$m axial and 20 $μ$m lateral resolution 2D and 3D imagin…
We report on the fabrication and mid-infrared transmission properties of free-standing thin metal films, periodically patterned with holes at periods down to 2 microns and area of 3x3 mm2. Square grids were fabricated by electron beam lithography and deep-etching techniques and display substrateless holes, with the metal being supported by a patterned dielectric silicon nitride membrane. The mid-infrared transmission spectra of the substrateless grid display extraordinary transmission peaks and resonant absorption lines with a Q-factor up to 22. These spectral features are due to the interacti…
