ORCID Profile
0000-0002-1540-9920
Current Organisation
Centre National de la Recherche Scientifique
Does something not look right? The information on this page has been harvested from data sources that may not be up to date. We continue to work with information providers to improve coverage and quality. To report an issue, use the Feedback Form.
Publisher: The Optical Society
Date: 04-11-2015
Publisher: AIP Publishing
Date: 18-01-2010
DOI: 10.1063/1.3273056
Abstract: The use of integrated photonic structures to tailor the behavior of light is extremely promising for optimizing performance and for introducing advanced functionalities into optoelectronic devices. We demonstrate a powerful method based on photonic-band engineering which allows the optimization of the resonator quality factors of devices operating on band-edge photonic-crystal states. We also show that carefully designed π-shifts in two-dimensional photonic-resonators give enhanced beam properties. The application of these general techniques to terahertz quantum cascade lasers yields improved maximum operating temperatures, and angularly narrow, single-lobed surface emission of ≈12°×8°. The devices operate at ≈2.8/2.9 THz, with peak output powers of 5 mW at 78 K.
Publisher: Springer Science and Business Media LLC
Date: 2009
DOI: 10.1038/NATURE07636
Abstract: Semiconductor lasers based on two-dimensional photonic crystals generally rely on an optically pumped central area, surrounded by un-pumped, and therefore absorbing, regions. This ideal configuration is lost when photonic-crystal lasers are electrically pumped, which is practically more attractive as an external laser source is not required. In this case, in order to avoid lateral spreading of the electrical current, the device active area must be physically defined by appropriate semiconductor processing. This creates an abrupt change in the complex dielectric constant at the device boundaries, especially in the case of lasers operating in the far-infrared, where the large emission wavelengths impose device thicknesses of several micrometres. Here we show that such abrupt boundary conditions can dramatically influence the operation of electrically pumped photonic-crystal lasers. By demonstrating a general technique to implement reflecting or absorbing boundaries, we produce evidence that whispering-gallery-like modes or true photonic-crystal states can be alternatively excited. We illustrate the power of this technique by fabricating photonic-crystal terahertz (THz) semiconductor lasers, where the photonic crystal is implemented via the sole patterning of the device top metallization. Single-mode laser action is obtained in the 2.55-2.88 THz range, and the emission far field exhibits a small angular ergence, thus providing a solution for the quasi-total lack of directionality typical of THz semiconductor lasers based on metal-metal waveguides.
Publisher: The Optical Society
Date: 05-06-2012
DOI: 10.1364/OE.20.013738
Publisher: The Optical Society
Date: 27-11-2017
Publisher: AIP Publishing
Date: 22-06-2009
DOI: 10.1063/1.3158592
Publisher: Springer Science and Business Media LLC
Date: 03-03-2021
DOI: 10.1038/S41467-021-21659-6
Abstract: Millimeter wave (mmWave) generation using photonic techniques has so far been limited to the use of near-infrared lasers that are down-converted to the mmWave region. However, such methodologies do not currently benefit from a monolithic architecture and suffer from the quantum defect i.e. the difference in photon energies between the near-infrared and mmWave region, which can ultimately limit the conversion efficiency. Miniaturized terahertz (THz) quantum cascade lasers (QCLs) have inherent advantages in this respect: their low energy photons, ultrafast gain relaxation and high nonlinearities open up the possibility of innovatively integrating both laser action and mmWave generation in a single device. Here, we demonstrate intracavity mmWave generation within THz QCLs over the unprecedented range of 25 GHz to 500 GHz. Through ultrafast time resolved techniques, we highlight the importance of modal phases and that the process is a result of a giant second-order nonlinearity combined with a phase matched process between the THz and mmWave emission. Importantly, this work opens up the possibility of compact, low noise mmWave generation using modelocked THz frequency combs.
Publisher: The Optical Society
Date: 27-06-2014
DOI: 10.1364/OL.39.003962
Publisher: AIP Publishing
Date: 07-03-2011
DOI: 10.1063/1.3560980
Abstract: We exploit the modal confinement properties of metal-metal ridge waveguides to investigate the effect of reducing the thickness of the active laser cores in both terahertz and mid-infrared quantum cascade lasers. Devices with active regions over 55 times thinner than the free-space emission wavelength are demonstrated. They show only a modest increase in threshold current density compared with conventional-thickness devices. The limited increase in threshold is possibly due to a parasitic current channel in addition to the radiative current channel. These structures could be useful for the development of ultra-low volume lasers.
Publisher: AIP Publishing
Date: 22-11-2010
DOI: 10.1063/1.3519985
Abstract: 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.
Publisher: Optica Publishing Group
Date: 12-2009
Publisher: AIP Publishing
Date: 05-12-2016
DOI: 10.1063/1.4969067
Abstract: We report on the realization of a monolithically integrated master-oscillator power- lifier architecture in a terahertz quantum cascade laser (THz-QCL) with a metal-metal waveguide. The master-oscillator section is a first-order distributed feedback (DFB) laser. Instead of using a thick anti-reflection coating, we exploit a diffraction grating together with an absorbing boundary in the power- lifier section to efficiently extract the laser radiation and suppress the self-lasing in it. The devices demonstrate a stable generation and power lification of single-mode emission. The lification factor is about 5, and the output power is approximately twice that of the standard second-order DFB lasers fabricated from the same material. Emission beam pattern with a ergence angle of ∼18 × 40° is achieved. Our work provides an avenue for the realization of single-mode THz-QCLs with high output power and good beam quality.
Publisher: AIP Publishing
Date: 03-06-2013
DOI: 10.1063/1.4808385
Abstract: We demonstrate the generation of high order terahertz (THz) frequency sidebands (up to 3rd order) on a near infrared (NIR) optical carrier within a THz quantum cascade laser (QCL). The NIR carrier is resonant with the interband transition of the quantum wells composing the QCL, allowing the nonlinearity to be enhanced and leading to frequency mixing. A phonon depopulation based QCL with a double metal cavity was used to enhance the intracavity power density and to demonstrate the higher order sidebands. The 1st order sideband intensity shows a linear dependence with THz power corresponding to a single THz photon, while the second order sideband has a quadratic dependence implying a two THz photon interaction and hence a third order susceptibility. These measurements are compared to the photoluminescence and the QCL bandstructure to identify the states involved, with the lowest conduction band states contributing the most to the sideband intensity. We also show that the interaction for the second order sideband corresponds to an enhanced direct third order susceptibility χ(3) of ∼7 × 10−16(m/V)2, two orders of magnitude greater than the bulk value.
Publisher: The Optical Society
Date: 31-08-2011
DOI: 10.1364/OE.19.018155
Publisher: AIP Publishing
Date: 02-12-2019
DOI: 10.1063/1.5116351
Abstract: We demonstrate a sensitive and compact terahertz heterodyne detection system based on a quantum cascade laser (QCL) as a local oscillator and a hot electron bolometer (HEB) as a mixer. It relies on an original optical coupling scheme where the terahertz (THz) signal to be detected and the local oscillator (LO) signal are coupled to the HEB from both sides of the integrated lens/antenna mixer. The THz signal of interest impinges on the front side through the silicon lens while the LO onto the rear (air) side. This concept allows us to remove the beam splitter usually employed in terahertz heterodyne receivers. The mixer consists of a Niobium Nitride HEB with a log-spiral planar antenna mounted on the flat side of a hyperhemispherical silicon lens. The local oscillator of the heterodyne detector is a low power consumption and low beam ergence 3rd-order distributed feedback laser with single mode emission at the target frequency of 2.7 THz. The coupling between the QCL and the HEB has been further optimized, using a dielectric hollow waveguide that reliably increases the laser beam directivity and permits us to pump the HEB into its most sensitive state through the air side of the planar antenna. We have measured a noncorrected double sideband receiver noise temperature of 880 K at 2.7 THz.
Publisher: The Optical Society
Date: 06-03-2015
DOI: 10.1364/OE.23.006915
Publisher: AIP Publishing
Date: 03-04-2017
DOI: 10.1063/1.4979536
Abstract: Interdigitated photoconductive (iPC) switches are powerful and convenient devices for time-resolved spectroscopy, with the ability to operate both as sources and detectors of terahertz (THz) frequency pulses. However, reflection of the emitted or detected radiation within the device substrate itself can lead to echoes that inherently limit the spectroscopic resolution achievable for their use in time-domain spectroscopy (TDS) systems. In this work, we demonstrate a design of low-temperature-grown-GaAs (LT-GaAs) iPC switches for THz pulse detection that suppresses such unwanted echoes. This is realized through the growth of a buried multilayer LT-GaAs structure that retains its ultrafast properties, which, after wafer bonding to a metal-coated host substrate, results in an iPC switch with a metal plane buried at a subwavelength depth below the LT-GaAs surface. Using this device as a detector, and coupling it to an echo-less iPC source, enables echo-free THz-TDS and high-resolution spectroscopy, with a resolution limited only by the temporal length of the measurement governed by the mechanical delay line used. As a proof-of-principle, the 212-221 and the 101-212 rotational lines of water vapor have been spectrally resolved, demonstrating a spectral resolution below 10 GHz.
Publisher: Optica Publishing Group
Date: 22-05-2009
DOI: 10.1364/OE.17.009491
Abstract: We demonstrate a framework to understand and predict the far-field emission in terahertz frequency photonic-crystal quantum cascade lasers. The devices, which employ a high-performance three-well active region, are lithographically tunable and emit in the 104-120 microm wavelength range. A peak output power of 7 mW in pulsed mode is obtained at 10 K, and the typical device maximum operating temperature is 136 K. We identify the photonic-crystal band-edge states involved in the lasing process as originating from the hexapole and monopole modes at the G point of the photonic band structure, as designed. The theoretical far-field patterns, obtained via finite-difference time-domain simulations, are in excellent agreement with experiment. Polarization measurements further support the theory, and the role of the bonding wires in the emission process is elucidated.
Publisher: AIP Publishing
Date: 03-03-2014
DOI: 10.1063/1.4866661
Publisher: AIP Publishing
Date: 08-09-2020
DOI: 10.1063/5.0018865
Abstract: Scanning-probe-assisted mid-infrared nano-spectroscopy is employed to reveal the polaritonic dispersion of in idual MIM (metal-insulator-metal) square patch antennas whose modes can be strongly coupled to a mid-infrared intersubband transition. The patch antenna side length L sets the resonances between λ = 5.5 μm and 12.5 μm. The active region consists of a highly doped AlInAs/InGaAs/AlInAs single quantum well that presents an intersubband transition at 1190 cm−1 (λ = 8.4 μm). When the patch antenna optical resonance approaches and matches the intersubband transition frequency (L ∼ 1.8 μm), a clear anticrossing behavior—evidence of strong coupling—is observed in the near-field scattering phase spectra of in idual antennas. The measured Rabi splitting is 4.5 THz. The near-field scattering spectra agree with the far-field extinction spectra acquired on arrays of identical antennas.
Publisher: AIP Publishing
Date: 11-2021
DOI: 10.1063/5.0065591
Abstract: We present a mid-IR (λ ∼ 8.3 μm) quantum well infrared photodetector (QWIP) fabricated on a mid-IR transparent substrate, allowing photodetection with illumination from either the front surface or through the substrate. The device is based on a 400 nm-thick GaAs/AlGaAs semiconductor QWIP heterostructure enclosed in a nanostructured metal–insulator–metal cavity and hosted on a mid-IR transparent ZnSe substrate. Metallic stripes are symmetrically patterned by e-beam lithography on both sides of the active region. The detector spectral coverage spans from λ ∼ 7.15 to λ ∼ 8.7 μm by changing the stripe width L—from L = 1.0 to L = 1.3 μm—thus frequency-tuning the optical cavity mode. Both micro-FTIR passive optical characterizations and photocurrent measurements of the two-port system are carried out. They reveal a similar spectral response for the two detector ports with an experimentally measured TBLIP of ∼200 K.
Publisher: AIP Publishing
Date: 15-12-2008
DOI: 10.1063/1.3043795
Abstract: We elucidate the effects of the lateral mode structure on the far field pattern of metal-metal ridge-waveguide terahertz quantum cascade lasers. By introducing a 6-μm-wide metal gap on the top metal contact, we suppress odd-parity lateral modes and drastically modify the far field pattern. Measurements are in good qualitative agreement with full three-dimensional finite-difference-time-domain modeling. Experimental evidence of nonuniform current pumping on the intensity distribution of the guided mode (and hence the far field pattern) is also presented and explained in terms of gain guiding.
Publisher: The Optical Society
Date: 27-01-2016
DOI: 10.1364/OE.24.002174
Publisher: The Optical Society
Date: 12-2016
DOI: 10.1364/OE.24.028583
Publisher: SPIE
Date: 27-01-2017
DOI: 10.1117/12.2251405
Publisher: AIP Publishing
Date: 07-03-2016
DOI: 10.1063/1.4943167
Abstract: We demonstrate strong light-matter coupling in three dimensional terahertz meta-atoms at room temperature. The intersubband transition of semiconductor quantum wells with a parabolic energy potential is strongly coupled to the confined circuital mode of three-dimensional split-ring metal-semiconductor-metal resonators that have an extreme sub-wavelength volume (λ/10). The frequency of these lumped-element resonators is controlled by the size and shape of the external antenna, while the interaction volume remains constant. This allows the resonance frequency to be swept across the intersubband transition and the anti-crossing characteristic of the strong light-matter coupling regime to be observed. The Rabi splitting, which is twice the Rabi frequency (2ΩRabi), amounts to 20% of the bare transition at room temperature, and it increases to 28% at low-temperature.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2012
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-10-2019
Abstract: We bring to light the complex interplay of optical nonlinearities in quantum structures.
Publisher: Wiley
Date: 07-2017
Publisher: Springer Science and Business Media LLC
Date: 17-07-2012
DOI: 10.1038/NCOMMS1958
Abstract: Symmetric and antisymmetric band-edge modes exist in distributed feedback surface-emitting semiconductor lasers, with the dominant difference being the radiation loss. Devices generally operate on the low-loss antisymmetric modes, although the power extraction efficiency is low. Here we develop graded photonic heterostructures, which localize the symmetric mode in the device centre and confine the antisymmetric modes close to the laser facet. This modal spatial separation is combined with absorbing boundaries to increase the antisymmetric mode loss, and force device operation on the symmetric mode, with elevated radiation efficiency. Application of this concept to terahertz quantum cascade lasers leads to record-high peak-power surface emission (>100 mW) and differential efficiencies (230 mW A(-1)), together with low- ergence, single-lobed emission patterns, and is also applicable to continuous-wave operation. Such flexible tuning of the radiation loss using graded photonic heterostructures, with only a minimal influence on threshold current, is highly desirable for optimizing second-order distributed feedback lasers.
Publisher: American Physical Society (APS)
Date: 04-06-2010
Publisher: AIP Publishing
Date: 06-06-2011
DOI: 10.1063/1.3597411
Abstract: We report the development of a scattering-type near-field scanning optical microscope (sNSOM) which operates at temperatures down to 100 K with a scanning range of up to 400 μm. We have used this sNSOM to map the electromagnetic near-field on mid-IR and terahertz (THz) surface emitting quantum cascade lasers with photonic-crystal resonators. Mid-IR devices operate at λ=7.5 μm (40 THz) while THz devices operate at λ≈110 μm (2.7 THz). The near-field images—in agreement with numerical calculations—demonstrate an instrument resolution of 100's nm.
Publisher: AIP Publishing
Date: 27-09-2010
DOI: 10.1063/1.3489941
Abstract: Terahertz frequency photonic-crystal quantum cascade lasers allow directional and controllable surface emission while at the same time functioning efficiently well above liquid nitrogen temperature. Through an in-depth understanding of the mechanism underlying surface emission, we demonstrate optimized devices with significantly reduced absolute threshold currents. We are able to reduce the device surface area by more than a factor of two, while maintaining angularly narrow, single-lobed surface emission with a ergence of ≈10°×10°. The devices emit at ∼2.8–2.9 THz, with maximum operating temperatures in the range 80–150 K.
No related grants have been discovered for Raffaele Colombelli.