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On the performance of wavelength meters: Part 1a??consequences for medium-to-high-resolution laser spectroscopy
摘要： Present-day laser-spectroscopy experiments increasingly rely on modern commercial devices to monitor, stabilize, and scan the wavelength of their probe laser. Recently, new techniques are capable of achieving unprecedented levels of precision on atomic and nuclear observables, pushing these devices to their performance limits. Considering the fact that these observables themselves are deduced from the frequency difference between specific atomic resonances, in the order of MHz–GHz, the uncertainty on the output of the device measuring the wavelength is often directly related to the final systematic uncertainty on the experimental results. Owing to its importance, the performance of several commercial wavelength meters was compared against different reference sources, including a Scanning Fabry–Pérot Interferometer (SFPI) and a frequency comb. Reproducible, wavelength- and device-dependent disagreements are observed, potentially skewing the experimental output at high precision. In this paper, a practical and relatively inexpensive wavelength meter characterization procedure is presented and validated. This method is capable of improving the precision on wavelength differences considerably depending on the device, while together with a second investigation that is published separately, (K?nig et al., in Appl Phys B, 2020), it offers a full description of the expected wavelength meter performance for users.
关键词： frequency comb,hyperfine structure,laser spectroscopy,wavelength meters,Scanning Fabry–Pérot Interferometer
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE CHILEAN Conference on Electrical, Electronics Engineering, Information and Communication Technologies (CHILECON) - Valparaiso, Chile (2019.11.13-2019.11.27)] 2019 IEEE CHILEAN Conference on Electrical, Electronics Engineering, Information and Communication Technologies (CHILECON) - Fourier-Bessel Shapes in Output Photocurrents and Frequency Chirping Effects from Laser Fields
摘要： Record low values in this material system of threshold current density, particularly at elevated temperature, are presented for InP quantum dot lasers. Lasers with Ga0 .5 8 In0 .4 2 P in the dot upper con?ning layer have the lowest threshold current densities, 138 A·cm?2 at 300 K, and 235 A·cm?2 at 350 K (77 °C) (2-mm lasers, uncoated facets). Gain-current density data suggests laser performance with an upper con?ning layer of Gax In1 ?xP with x = 0.54, 0.56 or 0.58 would be similar if not for the very low internal optical mode loss, αi of samples with x = 0.56 and 0.58. Gain measurements at ?xed inversion level suggest that increasing x content in Gax In1 ?xP increases gain at ?xed inversion level but samples with x = 0.54 also exhibit reduced recombination current density. The increasing recombination current density at elevated temperature due to thermal carrier spreading is signi?cantly reduced in samples with x = 0.56 and x = 0.58 but measurements at common operating points attribute this largely to the reduced αi for these samples and given the same αI , samples with x = 0.54, 0.56 and 0.58 would all bene?t from reduced effects due to thermal carrier spreading compared to x = 0.52.
关键词： Quantum dot devices,InP self-assembled quantum dots,semiconductor laser,short wavelength lasers,threshold current density,temperature sensitivity
更新于2025-09-23 15:21:01
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Topological Space-Time Photonic Transitions in Angular-Momentum-Biased Metasurfaces
摘要： In this paper, topological space-time photonic transition of light in angular-momentum-biased metasurfaces is established, which yields a superposition of orbital-angular-momentum (OAM)-carrying beams at distinct frequency harmonics upon scattering whose topological charges and frequency shifts are correlated. A reflective dielectric metasurface is considered that consists of silicon nanodisk heterostructures integrated with indium-tin-oxide and gate dielectric layers placed on a back mirror forming a dual-gated field effect modulator. The metasurface is divided into several azimuthal sections wherein the nanodisk heterostructures are interconnected via biasing lines. Addressing each azimuthal section with radio-frequency biasing signals separately allows for flexible implementation of different spatiotemporal modulation profiles. Active tuning of OAM states with high mode-purity is demonstrated, which yields minimal cross-talk between OAM channels in a mode-multiplexed communication system. Moreover, the role of spatiotemporal modulation profile on the spectral and spatial diversity of OAM states is explored. It is shown that angular-momentum-biased metasurfaces allow opportunities for hybridized mode-division and wavelength-division multiple access through multiplexing and multicasting across distinct OAM states and wavelengths. The nonreciprocity of topological space-time photonic transitions across the temporal frequency domain and Hilbert space of OAM states is also investigated giving rise to distinct twisted light channels in up- and down-links.
关键词： orbital angular momentum,topological space-time photonic transitions,time-modulated metasurfaces,mode-multiplexing,wavelength-division multiplexing
更新于2025-09-23 15:21:01
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Room Temperature Graphene Mid-Infrared Bolometer with a Broad Operational Wavelength Range
摘要： The last decade has witnessed the realization of numerous different types of graphene photodetectors with a strong focus on the visible and near-infrared spectral range, in which various high-performance photodetectors exist based on traditional materials such as silicon and III-V compound semiconductors. However, high-speed mid-infrared photodetection at room-temperature is still an unsolved challenge, despite its importance in applications such as security, sensing, and imaging. Here we address this challenge by demonstrating that high-quality graphene is an ideal high-speed bolometric material for the less-explored yet critical mid-infrared photodetection at room temperature, due to its broadband absorption, small heat capacity, and remarkably large temperature coefficient of resistance (TCR) of up to around 1% per Kelvin, which is comparable to that of commercial bolometric materials. We demonstrate a device based on graphene encapsulated in hexagonal boron nitride (hBN) exhibiting decent extrinsic responsivities of 5.1-1.4 mA/W in 3.4-12 μm wavelength range at room temperature, and further predict a detection bandwidth of at least 47 MHz. Our demonstration lays the foundations for graphene high-speed mid-infrared technologies.
关键词： high-quality graphene,broad wavelength range,scattering channels,Mid-infrared bolometer,temperature coefficient of resistance
更新于2025-09-23 15:21:01
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Microwave behavior of a monolithic dual-wavelength DFB laser based on current injection model
摘要： A driving current based model describing the optical heterodyne output of a monolithic dual-wavelength DFB laser is established. The linear relationship between the driving current and the laser output wavelength was applied to obtain the simple equation for this purpose. Actual measured data from the real devices were used for the initial parameter extraction and the practical model can then be built. By using this model, the influence of different laser parameters towards the radio frequency signal generation and different current configuration on the output characteristic can be demonstrated. This can facilitate the future design of such integrated photonic devices.
关键词： Dual-wavelength,Distributed feedback (DFB) laser,Monolithic
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Oxidative segregation of Group V dopants in CdTe solar cells
摘要： Dual-pump driven, dispersion-synthesized parametric mixers have been identified as an efficient means for wavelength multicasting. In particular, four-mode phase-sensitive (PS) architecture, seeded by frequency-locked and phase-correlated four input optical signals, allows the parametric multicasting operated with ultralow noise and regenerative properties. To further corroborate the superiorities of the multimode PS operation, degenerate one- and three-mode PS parametric multicasting were numerically and experimentally compared, in terms of stability, phase manipulation, gain, and conversion efficiency, as well as noise performance.
关键词： wavelength multicasting,signal replication,One-mode phase-sensitive process,parametric mixer,three-mode phase-sensitive process
更新于2025-09-23 15:21:01
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[IEEE 2019 IEEE Workshop on Power Electronics and Power Quality Applications (PEPQA) - Manizales, Colombia (2019.5.30-2019.5.31)] 2019 IEEE Workshop on Power Electronics and Power Quality Applications (PEPQA) - Determination and Performance Analysis of the Norton Equivalent Models for Fluorescents and LED Recessed Lightings
摘要： For long-wavelength space-based radars, such as the P-band radar on the recently selected European Space Agency BIOMASS mission, system distortions (crosstalk and channel imbalance), Faraday rotation, and system noise all combine to degrade the measurements. A first-order analysis of these effects on the measurements of the polarimetric scattering matrix is used to derive differentiable expressions for the errors in the polarimetric backscattering coefficients in the presence of Faraday rotation. Both the amplitudes and phases of the distortion terms are shown to be important in determining the errors and their maximum values. Exact simulations confirm the accuracy and predictions of the first-order analysis. Under an assumed power-law relation between σhv and the biomass, the system distortions and noise are converted into biomass estimation errors, and it is shown that the magnitude of the deviation of the channel imbalance from unity must be 4–5 dB less than the crosstalk, or it will dominate the error in the biomass. For uncalibrated data and midrange values of biomass, the crosstalk must be less than ?24 dB if the maximum possible error in the biomass is to be within 20% of its true value. A less stringent condition applies if the amplitudes and phases of the distortion terms are considered random since errors near the maximum possible are very unlikely. For lower values of the biomass, the noise becomes increasingly important because the σhv signal-to-noise ratio is smaller.
关键词： Biomass,Faraday rotation,polarimetric measurements,system distortion,calibration,long-wavelength radar
更新于2025-09-23 15:21:01
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Photogating-controlled ZnO photodetector response for visible to near-infrared light
摘要： Over the last several decades, as a direct wide band gap semiconductor, zinc oxide (ZnO) nanomaterial has attracted lots of attention. However, the widely investigated ZnO materials are strongly limited in fast-response and broadband photodetectors due to their inherent weaknesses, so effective structure or mechanism of ZnO nanostructure photodetector is urgent. In this work, a photogating-controlled photodetector based on ZnO nanosheet-HfO2-lightly doped Si architecture was demonstrated. Its performance was improved significantly by the photogating-controlled local field at Si and HfO2 interfaces compared to other published work of ZnO. Consequently, the photodetector not only effectively balance the responsivity (as high as 5.6 A W-1) and response time (400 μs), but also broadens the response wavelength of the ZnO-based photodetectors from visible to near-infrared (~1200 nm). Additionally, the photogating-controlled ZnO photodetector enables high-resolution imaging both in visible and near-infrared bands. Our photogating-controlled ZnO photodetectors not only exemplify the control ability of the gate electrode in high mobility materials but also provide ideas for fast speed and high responsivity detection of high mobility materials.
关键词： ZnO nanosheet,photogating-controlled photodetectors,response wavelength,high-resolution imaging
更新于2025-09-23 15:21:01
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Laser-wavelength and intensity dependence of electron-nuclear energy sharing in dissociative ionization of
摘要： We experimentally and theoretically study the photoelectron-nuclear energy sharing mechanism of the correlated dynamics between the photoelectrons and the fragmented ions in the dissociative ionization of H2 with respect to the laser intensity at the wavelengths λ = 395 nm and λ = 790 nm. We show that the prominent photoelectron-nuclear energy sharing along the back-diagonal lines is only observed for 395 nm at lower intensities, which is absent for increased intensities at 395 nm and for 790 nm lasers over a wide range of intensities. Based on a quantum mechanical model that includes the correlation between the photoelectron and the parent ion, we show that bond hardening has a significant effect on the photoelectron-nuclear energy sharing. The resonant states of the neutral hydrogen molecule during strong-field ionization and the distribution of vibrational states of molecular ions determine the joint energy spectrum of photoelectrons and nuclei. The study provides an intuitive and comprehensive description and understanding of the correlated photoelectron-nuclear dynamics in the dissociative ionization.
关键词： dissociative ionization,photoelectron-nuclear energy sharing,wavelength dependence,laser intensity,H2
更新于2025-09-23 15:21:01
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Mid-Wavelength Infrared Responsivity of Colloidal Quantum Dot/Organic Hybrid Photodetectors
摘要： Colloidal quantum dot/organic hybrid materials approach offer a path toward engineering solution-processed photodetectors with extended spectral responsivity in the infrared. We demonstrate this approach in the technologically important thermal infrared region of mid-wavelength infrared, utilizing a solution blend of Ag2Se colloidal quantum dots and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We report on the device fabrication and their room temperature optical, electrical, and optoelectronic properties. At room temperature, a responsivity of 0.2 mA/W was measured under 5 μm irradiation and 5 V bias. The new hybrid optoelectronic film demonstrated the advantage of cost-effectiveness and greater fabrication versatility than the single crystal or epitaxial semiconductors that comprise today’s infrared technologies.
关键词： Colloidal quantum dots,Photodetectors,Mid-wavelength infrared,Organic hybrid,Responsivity
更新于2025-09-23 15:21:01