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Infrared subwavelength focusing metasurfaces for harvesting heat from the Eartha??s back radiation
摘要： In this paper, we introduce two different metasurfaces that can achieve subwavelength focusing of the electromagnetic radiation in the infrared range with transmission ef?ciencies reaching 46% and 74.33% in silicon and thus they can be integrated in heat harvesting applications. We made our designs at the wavelength of 10 μm which is the peak of the back radiation of the Earth. In designing our metasurfaces in the infrared range, we used the phase modulation techniques that proved to be useful in the visible domain. The best focusing resolution achieved in our metasurfaces is 0.26λ (super-focusing). In addition to heat harvesting, the two proposed metasurfaces can be useful in other compact applications that require manipulating the mid-infrared radiation on a very small scale. We used copper and silicon in our metasurfaces which are speci?cally suitable for the mid-infrared range besides being CMOS compatible. In this paper, we also explained how heat can be harvested from the introduced metasurfaces using the Seebeck effect.
关键词： plasmonics,subwavelength focusing,planar lens,phase modulation,heat harvesting,metasurface,mid-infrared focusing
更新于2025-09-19 17:13:59
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Quantum cascade laser based, fiber coupled demultiplexed mid-infrared local oscillator for cryogenic applications
摘要： We have developed a fiber coupled demultiplexed local oscillator (LO) source for cryogenic applications based on a distributed feedback quantum cascade laser (QCL) at an operating wavelength of 10.6 μm. The coupling scheme relies on the combination of a phase grating generating multiple LO beams and a polycrystalline fiber delivering the demultiplexed LO signal to a superconducting mixer at 4 K in a closed-cycle cryostat. This scheme eases the use of a beam splitter in front of the mixer. Reflection phase grating generating 2 × 2 beams has been achieved with a total power efficiency of 64% based on a gold covered etched silicon nanostructure. The diffraction beam has been readily coupled into a 2 m long polycrystalline fiber, where a single-lobe circular beam has been delivered at the fiber output. By aligning the fiber core position to the center of a superconducting hot electron bolometer mixer at the rear side, we demonstrate the application of a fiber coupled demultiplexed QCL source for pumping the superconducting mixer with adequate LO power.
关键词： cryogenic applications,fiber coupled,local oscillator,quantum cascade laser,mid-infrared
更新于2025-09-19 17:13:59
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Dysprosium Mida??Infrared Lasers: Current Status and Future Prospects
摘要： 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 μm (in addition to 4:3 μm 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 dysprosium ion are examined and the major developments that have led to this resurgence of interest and subsequent record mid-infrared laser performance are surveyed. Also mid-infrared applications of emerging dysprosium lasers are highlighted, in addition to surveying the many opportunities that lie ahead.
关键词： mid-infrared,dysprosium,fiber laser
更新于2025-09-19 17:13:59
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High Conversion Efficiency, Mid-Infrared Pulses Generated via Burst-Mode Fiber Laser Pumped Optical Parametric Oscillator
摘要： We present a mid-infrared optical parametric oscillator (OPO) with a high pump-to-idler conversion efficiency from 1.06 μm to 3.8 μm, which was quasi-synchronously pumped by a burst-mode fiber laser. The pump pulse was specially designed with a rectangular profile in temporal, which was composed of hundreds of ultrashort sub-pulses. By applying the quasi-synchronous pumping scheme, the buildup time of the parametric signal pulse could be minimized. No back-conversion effect was observed when the pump peak power was increased. A maximum pump-to-idler conversion efficiency of 19.6% was achieved when the number of intra-burst sub-pulses was set to be 240. By increasing the number of intra-burst sub-pulses to be about 480, the maximum average output power of 7.9 W at 3.8 μm was realized under pump power of 45.3 W. The corresponding pump-to-idler conversion efficiency was computed to be about 17.5%. The experimental results show an improvement of 40% in pump-to-idler conversion efficiency for this quasi-synchronously pumped OPO when compared with the conventional long laser pulse pumped OPO.
关键词： burst-mode fiber laser,quasi-synchronously pumped,mid-infrared,optical parametric oscillator
更新于2025-09-19 17:13:59
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<i>(Invited)</i> Mid-Infrared Colloidal Quantum Dot Based Nanoelectronics and Nano-Optoelectronics
摘要： Electronic and optoelectronic devices fabricated from colloidal quantum dots (CQDs) provide a promising path toward realizing low-cost devices with greatly simplified device fabrication procedure, owing to their solution-processability. The impact that CQD technology would bring is expected to be significant, especially in the mid-infrared application areas, which is currently dominated by epitaxial semiconductor technologies. In this work, we introduce a new generation of infrared CQDs, namely Ag2Se CQDs, which has been recently uncovered to show distinct optical absorption in the mid-infrared. We report on the fabrication of solution-processed photoconductive photodetectors and discuss our analyses on the electronic and optoelectronic characteristics of our devices. We also demonstrate the feasibility of mid-infrared photodetection with a measured peak responsivity of 0.16 mA/W at 4 μm under room temperature operation.
关键词： Ag2Se,solution-processability,photodetectors,mid-infrared,colloidal quantum dots
更新于2025-09-19 17:13:59
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Noninvasive blood glucose detection by Quantum Cascade Laser
摘要： Quantum Cascade Laser (QCL) was invented in late 90s as a promising mid-infrared light source and contributed to the field of industry, military, medicine, and biology. The room temperature operation, watt-level output power, compact size, and wide tuning capability of this laser advanced the field of noninvasive blood glucose detection by exploring transmission, absorption, and photoacoustic spectroscopy. This review provides a complete overview of the recent progress and technical details of these spectroscopy techniques, using QCL as an infrared light source for detecting blood glucose concentration for diabetic patients.
关键词： transmission spectroscopy,Quantum Cascade Laser,mid-infrared,noninvasive blood glucose detection,photoacoustic spectroscopy,absorption spectroscopy
更新于2025-09-19 17:13:59
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Dynamic Ligand Surface Chemistry of Excited PbS Quantum Dots
摘要： The ligand shell around colloidal quantum dots mediates the electron and energy transfer processes that underpin their use in optoelectronic and photocatalytic applications. Here, we show that the surface chemistry of carboxylate anchoring groups of oleate ligands passivating PbS quantum dots undergoes significant changes when the quantum dots are excited to their excitonic states. We directly probe the changes of surface chemistry using time-resolved mid-infrared spectroscopy that records the evolution of the vibrational frequencies of carboxylate groups following excitation of the electronic states. The data reveal a reduction of the Pb?O coordination of carboxylate anchoring groups to lead atoms at the quantum dot surfaces. The dynamic surface chemistry of the ligands may increase their surface mobility in the excited state and enhance the ability of molecular species to penetrate the ligand shell to undergo energy and charge transfer processes that depend sensitively on distance.
关键词： surface chemistry,PbS quantum dots,ligand shell,colloidal quantum dots,time-resolved mid-infrared spectroscopy
更新于2025-09-19 17:13:59
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Determination of the electric field and its Hilbert transform in femtosecond electro-optic sampling
摘要： We demonstrate time-domain sampling of mid-infrared electric ?eld transients and their conjugate counterparts exploiting the dynamical Pockels effect. To this end, the complete polarization change of few-femtosecond probe pulses is studied. An intuitive picture based on a phasor representation is established before gaining quantitative understanding in experiment and theory. In the standard version of electro-optic sampling, the electric ?eld is determined by analyzing the change of ellipticity of the probe polarization. Beyond this, we ?nd that a temporal gradient of the input electric ?eld manifests itself in a rotation of the polarization ellipsoid of the probe. The relative contribution of sum- and difference-frequency mixing processes and their spectral distribution over the near-infrared probe bandwidth are identi?ed as key aspects. If one of these processes dominates, detecting ellipticity changes and polarization rotation as a function of time delay results in two wave forms which are Hilbert transforms of each other. Such conditions may be achieved by angle phase matching in birefringent materials or spectral ?ltering of the probe after the nonlinear interaction. In this case, a static phase introduced by birefringence or re?ection at metallic mirrors results in a speci?c phase shift of both time traces with respect to the input electric ?eld. Contributions from sum- and difference-frequency generation are found to be equivalent when using electro-optic sensors with isotropic refractive index. Polarization rotations in the low- and high-frequency parts of the probe then tend to cancel out. In this limit, spurious additional phase shifts do not change the phase of the detected transients. This fact leads to a robust recovery of the carrier-envelope phase of the input wave form. Clarifying the role of imperfections of superachromatic phase retarders completes our survey on proper determination of the electric ?eld and its conjugate variable.
关键词： polarization rotation,sum-frequency generation,difference-frequency generation,electro-optic sampling,Pockels effect,mid-infrared,Hilbert transform
更新于2025-09-19 17:13:59
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Investigation of Dy3+/Tm3+ co-doped ZrF4-BaF2-YF3-AlF3 fluoride glass for efficient 2.9?μm mid-infrared laser applications
摘要： Different doping concentrations of Dy3+/Tm3+ in ZrF4-BaF2-YF3-AlF3 (ZBYA) fluoride glass samples were prepared by the melt-quenching method. Spectroscopic properties were analyzed through absorption (from 200 to 3300 nm) and emission spectra (from 1200 to 3200 nm). The spontaneous radiative transition probability, branching ratio and radiative lifetime of various energy levels transition were calculated based on the Judd-Ofelt theory. The emission cross-section value of the 1 mol% Dy3+/1 mol% Tm3+ co-doped ZBYA sample at 2.9 μm were calculated as 3.79 10-21 cm2. Near- and mid-IR emission spectra of Dy3+/Tm3+ co-doped ZBYA-fluoride glass under the excitation of 808 nm laser diode were investigated and discussed. Analysis of the emission spectra and the energy transition process of Dy3+/Tm3+ co-doped glass indicated that the introduction of Tm3+ ions can effectively improve the mid-infrared fluorescence intensity of Dy3+ ions, thus the Dy3+/Tm3+ co-doped ZBYA-fluoride glass can be an excellent candidate material for 2.9 μm mid-infrared laser applications.
关键词： Dy3+/Tm3+ co-doped,mid-infrared laser,ZBYA fluoride glass
更新于2025-09-19 17:13:59
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Mid-infrared Polarized Emission from Black Phosphorus Light-Emitting Diodes
摘要： We demonstrate a mid-infrared light-emitting diode based on the 2D semiconductor black phosphorus (BP). The device is composed of a mechanically exfoliated BP/molybdenum disulfide heterojunction. Under forward bias, it emits polarized electroluminescence at λ = 3.68 μm, with room-temperature internal and external quantum efficiencies of ~1% and ~0.03%, respectively. In our structure, outcoupling losses are dominated by radiation towards the high refractive index substrate. The ability to tune the bandgap of BP, and consequently its emission wavelength with layer number, strain and electric field make these LEDs particularly attractive for heterointegration into mid-infrared photonic platforms.
关键词： heterostructures,2D materials,mid-infrared emitters,light-emitting diodes,Black phosphorus
更新于2025-09-19 17:13:59