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1.
Nano Lett ; 2020 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-32407632

##### RESUMO

Many photonic and plasmonic structures have been proposed to achieve ultra-subwavelength light confinement across the electromagnetic spectrum. Notwithstanding this effort, however, the efficient funneling of external radiation into nano-scale volumes remains problematic. Here we demonstrate a photonic concept that fulfills the seemingly incompatible requirements for both strong electromagnetic confinement and impedance matching to free space. Our architecture consists of antenna-coupled meta-atom resonators that funnel up to 90% of the incident radiation into an ultra-subwavelength semiconductor quantum well absorber of volume V= λ310-6. A significant fraction of the coupled electromagnetic energy is used to excite the electronic transitions in the quantum well, with photon absorption efficiency 550 times larger than the intrinsic value of the electronic dipole. This system opens important perspectives for ultra-low dark current quantum detectors and for the study of light-matter interaction in the extreme regimes of electronic and photonic confinement.

2.
Nat Commun ; 11(1): 835, 2020 Feb 11.
Artigo em Inglês | MEDLINE | ID: mdl-32047146

##### RESUMO

The fast modulation of lasers is a fundamental requirement for applications in optical communications, high-resolution spectroscopy and metrology. In the terahertz-frequency range, the quantum-cascade laser (QCL) is a high-power source with the potential for high-frequency modulation. However, conventional electronic modulation is limited fundamentally by parasitic device impedance, and so alternative physical processes must be exploited to modulate the QCL gain on ultrafast timescales. Here, we demonstrate an alternative mechanism to modulate the emission from a QCL device, whereby optically-generated acoustic phonon pulses are used to perturb the QCL bandstructure, enabling fast amplitude modulation that can be controlled using the QCL drive current or strain pulse amplitude, to a maximum modulation depth of 6% in our experiment. We show that this modulation can be explained using perturbation theory analysis. While the modulation rise-time was limited to ~800 ps by our measurement system, theoretical considerations suggest considerably faster modulation could be possible.

3.
Nature ; 578(7794): 246-250, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-32051601

##### RESUMO

Quantum cascade lasers are compact, electrically pumped light sources in the technologically important mid-infrared and terahertz region of the electromagnetic spectrum1,2. Recently, the concept of topology3 has been expanded from condensed matter physics into photonics4, giving rise to a new type of lasing5-8 using topologically protected photonic modes that can efficiently bypass corners and defects4. Previous demonstrations of topological lasers have required an external laser source for optical pumping and have operated in the conventional optical frequency regime5-8. Here we demonstrate an electrically pumped terahertz quantum cascade laser based on topologically protected valley edge states9-11. Unlike topological lasers that rely on large-scale features to impart topological protection, our compact design makes use of the valley degree of freedom in photonic crystals10,11, analogous to two-dimensional gapped valleytronic materials12. Lasing with regularly spaced emission peaks occurs in a sharp-cornered triangular cavity, even if perturbations are introduced into the underlying structure, owing to the existence of topologically protected valley edge states that circulate around the cavity without experiencing localization. We probe the properties of the topological lasing modes by adding different outcouplers to the topological cavity. The laser based on valley edge states may open routes to the practical use of topological protection in electrically driven laser sources.

4.
Biosci Biotechnol Biochem ; 84(4): 703-713, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31797734

##### RESUMO

MiR-381-3p and nuclear autoantigenic sperm protein (NASP) have regulatory functions in tumors. Whether NASP is targeted by miR-381-3p to influence biological characteristics of cancer in head-neck squamous cell carcinoma (HNSCC) cells was investigated. StarBase (version 3.0) found that the expression of NASP was increased with the down-regulation of miR-381-3p in laryngocarcinoma tissue, AMC-HN-3ï¼FaDuï¼HNE-3ï¼and Detroit 562 cell lines. MiR-381-3p could target NASP, reduce the expression of MMP-2 and MMP-9, Vimentin, repress the cell viability, invasion, and migration, and promote the expression of E-cadherin in AMC-HN-3 cells. Overexpressed NASP could increase the viability, migration and invasion rates in AMC-HN-3 cells, which could be partially reversed by overexpressed miR-381-3p. Thus, miR-381-3p targeted and suppressed NASP gene, reduced the viability, migration, invasion, EMT of HNSCC cells, demonstrating that miR-381-3p has the potential to be a therapeutic target in inhibiting the progression of HNSCC.

5.
Opt Lett ; 44(23): 5663-5666, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31774748

##### RESUMO

Owing to their intrinsic stability against optical feedback (OF), quantum cascade lasers (QCLs) represent a uniquely versatile source to further improve self-mixing interferometry at mid-infrared and terahertz (THz) frequencies. Here, we show the feasibility of detecting with nanometer precision, the deeply subwavelength ($\lt \lambda /6000$<λ/6000) mechanical vibrations of a suspended ${{\rm Si}_3}{{\rm N}_4}$Si3N4 membrane used as the external element of a THz QCL feedback interferometer. Besides representing an extension of the applicability of vibrometric characterization at THz frequencies, our system can be exploited for the realization of optomechanical applications, such as dynamical switching between different OF regimes and a still-lacking THz master-slave configuration.

6.
Opt Express ; 27(15): 20231-20240, 2019 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-31510121

##### RESUMO

Miniaturized frequency combs (FCs) can be self-generated at terahertz (THz) frequencies through four-wave mixing in the cavity of a quantum cascade laser (QCL). To date, however, stable comb operation is only observed over a small operational current range in which the bias-depended chromatic dispersion is compensated. As most dispersion compensation techniques in the THz range are not tunable, this limits the spectral coverage of the comb and the emitted output power, restricting potential applications in, for example, metrology and ultrashort THz pulse generation. Here, we demonstrate an alternative architecture that provides a tunable, lithographically independent, control of the free-running coherence properties of THz QCL FCs. This is achieved by integrating an on-chip tightly coupled mirror with the QCL cavity, providing an external cavity and hence a tunable Gires Tournois interferometer (GTI). By finely adjusting the gap between the GTI and the back-facet of an ultra-broadband, high dynamic range QCL, we attain wide dispersion compensation regions, where stable and narrow (~3 kHz linewidth) single beatnotes extend over an operation range that is significantly larger than that of dispersion-dominated bare laser cavity counterparts. Significant reduction of the phase noise is registered over the whole QCL spectral bandwidth (1.35 THz). This agile accommodation of a tunable dispersion compensator will help enable uptake of QCL-combs for metrological, spectroscopic and quantum technology-oriented applications.

7.
Nat Commun ; 10(1): 2938, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31270325

##### RESUMO

Miniaturized frequency comb sources across hard-to-access spectral regions, i.e. mid- and far-infrared, have long been sought. Four-wave-mixing based Quantum Cascade Laser combs (QCL-combs) are ideal candidates, in this respect, due to the unique possibility to tailor their spectral emission by proper nanoscale design of the quantum wells. We demonstrate full-phase-stabilization of a QCL-comb against the primary frequency standard, proving independent and simultaneous control of the two comb degrees of freedom (modes spacing and frequency offset) at a metrological level. Each emitted mode exhibits a sub-Hz relative frequency stability, while a correlation analysis on the modal phases confirms the high degree of coherence in the device emission, over different power-cycles and over different days. The achievement of fully controlled, phase-stabilized QCL-comb emitters proves that this technology is mature for metrological-grade uses, as well as for an increasing number of scientific and technological applications.

8.
Light Sci Appl ; 8: 43, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31044073

##### RESUMO

Random lasers are a class of devices in which feedback arises from multiple elastic scattering in a highly disordered structure, providing an almost ideal light source for artefact-free imaging due to achievable low spatial coherence. However, for many applications ranging from sensing and spectroscopy to speckle-free imaging, it is essential to have high-radiance sources operating in continuous-wave (CW). In this paper, we demonstrate CW operation of a random laser using an electrically pumped quantum-cascade laser gain medium in which a bi-dimensional (2D) random distribution of air holes is patterned into the top metal waveguide. We obtain a highly collimated vertical emission at ~3 THz, with a 430 GHz bandwidth, device operation up to 110 K, peak (pulsed) power of 21 mW, and CW emission of 1.7 mW. Furthermore, we show that an external cavity formed with a movable mirror can be used to tune a random laser, obtaining continuous frequency tuning over 11 GHz.

9.
Opt Express ; 27(7): 10221-10233, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-31045166

##### RESUMO

We report a coherent terahertz (THz) imaging system that utilises a quantum cascade laser (QCL) operating in pulsed-mode as both the source and detector. The realisation of a short-pulsed THz QCL feedback interferometer permits both high peak powers and improved thermal efficiency, which enables the cryogen-free operation of the system. In this work, we demonstrated pulsed-mode swept-frequency laser feedback interferometry experimentally. Our interferometric detection scheme not only permits the simultaneous creation of both amplitude and phase images, but inherently suppresses unwanted background radiation. We demonstrate that the proposed system utilising microsecond pulses has the potential to achieve 0.25 mega-pixel per second acquisition rates, paving the pathway to video frame rate THz imaging.

10.
Medicine (Baltimore) ; 98(7): e14412, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30762745

##### RESUMO

RATIONALE: posterior pharyngeal wall carcinomas located at the level of the cricoid cartilage is a rare occurrence. Surgical treatment is a dilemma owing to the retention of laryngeal function PATIENT CONCERNS:: A 56-year-old man underwent a "resection of left cervical tumor" at another hospital. Postoperative pathological report noted a left metastatic squamous cell carcinoma of the neck. Neck-enhanced computed tomography (CT) revealed thickening of the right posterior pharyngeal wall, and an image of soft tissue density was present on the posterior pharyngeal wall with a size of approximately 1.0â×â1.5âcm. DIAGNOSIS: Hypopharyngeal carcinoma (T1N2M0). INTERVENTIONS: We performed operation on a patient who suffered from posterior pharyngeal wall carcinomas at the level of the cricoid cartilage. The postoperative defects were repaired with posterior pharyngeal flaps. OUTCOMES: The patient with posterior pharyngeal flap after operation survived without necrosis, the neck wounds of patient healed in 1 stage, and the phonation, swallowing and respiratory function was good. LESSONS: The application of posterior pharyngeal flap to repair defects due to posterior pharyngeal wall carcinomas that were located at the level of the cricoid cartilage after resection is an effective reconstruction method that is easy to use and has excellent repair effects.

##### Assuntos
Carcinoma de Células Escamosas/cirurgia , Cartilagem Cricoide/cirurgia , Neoplasias Hipofaríngeas/cirurgia , Procedimentos Cirúrgicos Reconstrutivos/métodos , Retalhos Cirúrgicos , Carcinoma de Células Escamosas/patologia , Cartilagem Cricoide/patologia , Humanos , Neoplasias Hipofaríngeas/patologia , Masculino , Pessoa de Meia-Idade , Pescoço/patologia , Pescoço/cirurgia , Faringe/patologia , Faringe/cirurgia
11.
Opt Express ; 27(3): 2248-2257, 2019 Feb 04.
Artigo em Inglês | MEDLINE | ID: mdl-30732264

##### RESUMO

Intersubband (ISB) transitions in semiconductor multi-quantum well (MQW) structures are promising candidates for the development of saturable absorbers at terahertz (THz) frequencies. Here, we exploit amplitude and phase-resolved two-dimensional (2D) THz spectroscopy on the sub-cycle time scale to observe directly the saturation dynamics and coherent control of ISB transitions in a metal-insulator MQW structure. Clear signatures of incoherent pump-probe and coherent four-wave mixing signals are recorded as a function of the peak electric field of the single-cycle THz pulses. All nonlinear signals reach a pronounced maximum for a THz electric field amplitude of 11 kV/cm and decrease for higher fields. We demonstrate that this behavior is a fingerprint of THz-driven carrier-wave Rabi flopping. A numerical solution of the Maxwell-Bloch equations reproduces our experimental findings quantitatively and traces the trajectory of the Bloch vector. This microscopic model allows us to design tailored MQW structures with optimized dynamical properties for saturable absorbers that could be used in future compact semiconductor-based single-cycle THz sources.

12.
Sci Rep ; 8(1): 17648, 2018 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-30504784

##### RESUMO

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

13.
Nat Commun ; 9(1): 5181, 2018 11 30.
Artigo em Inglês | MEDLINE | ID: mdl-30504849

##### RESUMO

The original version of this Article contained an error in the Acknowledgements, which incorrectly omitted the following: 'We also acknowledge support from the Australian Research Council's Discovery Projects Funding Scheme (Grant DP 160 103910).' This has been corrected in both the PDF and HTML versions of the Article.

14.
Eur Arch Otorhinolaryngol ; 275(11): 2773-2781, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-30267217

##### RESUMO

PURPOSE: To identify potential molecular markers for induction chemotherapy of Laryngeal squamous cell carcinoma (LSCC). METHODS: Differently expressed genes between chemo-sensitive group (seven cases) and chemo-insensitive (five cases) group after induction chemotherapy by TPF were identified by microarrays. Bayes network and Random forest analyses were employed to identify core genes for induction chemotherapy. The diagnostic value of these core genes was also evaluated by ROC analysis. RESULTS: Six genes (SPP1, FOLR3, KYNU, LOC653219, ADH7 and XAGE1A) are highly expressed, while seven gene (CADM1, NDUFA4L2, CCND2, RARRES3, ERAP2, LYD6 and CNTNAP2) present significantly low expression. Among these genes, genes CADM1, FOLR3, KYNU, and CNTNAP2 are core candidates for LSCC chemo-sensitivity. And that the low expression of CADM1 may result in chemo-sensitivity, which leads to high expression of gene FOLR3 and KYNU, and low expression of gene CNTNAP2. Besides, ROC analysis shows that these four genes exhibit effective diagnostic value for induction chemo-sensitivity. CONCLUSIONS: CADM1 may be a potential molecular marker for LSCC induction chemotherapy, while CADM1, FOLR3, KYNU, and CNTNAP2 may provide essential guidance for LSCC diagnosis and follow-up treatment strategies.

##### Assuntos
Carcinoma de Células Escamosas/tratamento farmacológico , Carcinoma de Células Escamosas/genética , Quimioterapia de Indução , Neoplasias Laríngeas/tratamento farmacológico , Neoplasias Laríngeas/genética , Idoso , Proteínas de Transporte/genética , Molécula 1 de Adesão Celular/genética , Resistencia a Medicamentos Antineoplásicos , Feminino , Perfilação da Expressão Gênica , Marcadores Genéticos , Humanos , Masculino , Proteínas de Membrana/genética , Análise em Microsséries , Pessoa de Meia-Idade , Proteínas do Tecido Nervoso/genética , RNA Complementar/metabolismo
15.
Nat Commun ; 9(1): 3076, 2018 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-30082762

##### RESUMO

Single-mode frequency-tuneable semiconductor lasers based on monolithic integration of multiple cavity sections are important components, widely used in optical communications, photonic integrated circuits and other optical technologies. To date, investigations of the ultrafast switching processes in such lasers, essential to reduce frequency cross-talk, have been restricted to the observation of intensity switching over nanosecond-timescales. Here, we report coherent measurements of the ultrafast switch-on dynamics, mode competition and frequency selection in a monolithic frequency-tuneable laser using coherent time-domain sampling of the laser emission. This approach allows us to observe hopping between lasing modes on picosecond-timescales and the temporal evolution of transient multi-mode emission into steady-state single mode emission. The underlying physics is explained through a full multi-mode, temperature-dependent carrier and photon transport model. Our results show that the fundamental limit on the timescales of frequency-switching between competing modes varies with the underlying Vernier alignment of the laser cavity.

16.
Opt Express ; 26(14): 18423-18435, 2018 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-30114022

##### RESUMO

At terahertz (THz) frequencies, scattering-type scanning near-field optical microscopy (s-SNOM) based on continuous wave sources mostly relies on cryogenic and bulky detectors, which represents a major constraint for its practical application. Here, we devise a THz s-SNOM system that provides both amplitude and phase contrast and achieves nanoscale (60-70nm) in-plane spatial resolution. It features a quantum cascade laser that simultaneously emits THz frequency light and senses the backscattered optical field through a voltage modulation induced inherently through the self-mixing technique. We demonstrate its performance by probing a phonon-polariton-resonant CsBr crystal and doped black phosphorus flakes.

17.
Opt Lett ; 43(10): 2225-2228, 2018 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-29762559

##### RESUMO

We demonstrate a gas spectroscopy technique, using self-mixing in a 3.4 terahertz quantum-cascade laser (QCL). All previous QCL spectroscopy techniques have required additional terahertz instrumentation (detectors, mixers, or spectrometers) for system pre-calibration or spectral analysis. By contrast, our system self-calibrates the laser frequency (i.e., with no external instrumentation) to a precision of 630 MHz (0.02%) by analyzing QCL voltage perturbations in response to optical feedback within a 0-800 mm round-trip delay line. We demonstrate methanol spectroscopy by introducing a gas cell into the feedback path and show that a limiting absorption coefficient of â¼1×10-4 cm-1 is resolvable.

18.
Nat Commun ; 9(1): 1122, 2018 03 16.
Artigo em Inglês | MEDLINE | ID: mdl-29549267

##### RESUMO

Terahertz (THz) quantum cascade lasers (QCLs) have undergone rapid development since their demonstration, showing high power, broad-tunability, quantum-limited linewidth, and ultra-broadband gain. Typically, to address applications needs, continuous-wave (CW) operation, low-divergent beam profiles and fine spectral control of the emitted radiation, are required. This, however, is very difficult to achieve in practice. Lithographic patterning has been extensively used to this purpose (via distributed feedback (DFB), photonic crystals or microcavities), to optimize either the beam divergence or the emission frequency, or, both of them simultaneously, in third-order DFBs, via a demanding fabrication procedure that precisely constrains the mode index to 3. Here, we demonstrate wire DFB THz QCLs, in which feedback is provided by a sinusoidal corrugation of the cavity, defining the frequency, while light extraction is ensured by an array of surface holes. This new architecture, extendable to a broad range of far-infrared frequencies, has led to the achievement of low-divergent beams (10°), single-mode emission, high slope efficiencies (250 mW/A), and stable CW operation.

19.
Nature ; 556(7699): 85-88, 2018 04 05.
Artigo em Inglês | MEDLINE | ID: mdl-29579743

##### RESUMO

Room-temperature operation is essential for any optoelectronics technology that aims to provide low-cost, compact systems for widespread applications. A recent technological advance in this direction is bolometric detection for thermal imaging, which has achieved relatively high sensitivity and video rates (about 60 hertz) at room temperature. However, owing to thermally induced dark current, room-temperature operation is still a great challenge for semiconductor photodetectors targeting the wavelength band between 8 and 12 micrometres, and all relevant applications, such as imaging, environmental remote sensing and laser-based free-space communication, have been realized at low temperatures. For these devices, high sensitivity and high speed have never been compatible with high-temperature operation. Here we show that a long-wavelength (nine micrometres) infrared quantum-well photodetector fabricated from a metamaterial made of sub-wavelength metallic resonators exhibits strongly enhanced performance with respect to the state of the art up to room temperature. This occurs because the photonic collection area of each resonator is much larger than its electrical area, thus substantially reducing the dark current of the device. Furthermore, we show that our photonic architecture overcomes intrinsic limitations of the material, such as the drop of the electronic drift velocity with temperature, which constrains conventional geometries at cryogenic operation. Finally, the reduced physical area of the device and its increased responsivity allow us to take advantage of the intrinsic high-frequency response of the quantum detector at room temperature. By mixing the frequencies of two quantum-cascade lasers on the detector, which acts as a heterodyne receiver, we have measured a high-frequency signal, above four gigahertz (GHz). Therefore, these wide-band uncooled detectors could benefit technologies such as high-speed (gigabits per second) multichannel coherent data transfer and high-precision molecular spectroscopy.

20.
Opt Express ; 26(2): 1942-1953, 2018 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-29401915

##### RESUMO

A terahertz master-oscillation power-amplifier quantum cascade laser (THz-MOPA-QCL) is demonstrated where a grating coupler is employed to efficiently extract the THz radiation. By maximizing the group velocity and eliminating the scattering of THz wave in the grating coupler, the residue reflectivity is reduced down to the order of 10-3. A buried DFB grating and a tapered preamplifier are proposed to improve the seed power and to reduce the gain saturation, respectively. The THz-MOPA-QCL exhibits single-mode emission, a single-lobed beam with a narrow divergence angle of 18° × 16°, and a pulsed output power of 136 mW at 20 K, which is 36 times that of a second-order DFB laser from the same material.