Remote temperature control can be obtained by a long‐focus thermal lens that can focus heat fluxes into a spot far from the back surface of the lens and create a virtual thermal source/sink in the ...background material, around which the temperature field distribution can be remotely controlled by varying the parameters of the thermal lens. However, because of the lack of negative thermal conductivity, existing thermal lenses have extremely short focal lengths and cannot be used to remotely control the temperature field around the virtual thermal source/sink. In this study, a general approach is proposed to equivalently realize materials with negative thermal conductivity using elaborately distributed active thermal metasurfaces (ATMSs). Subsequently, the proposed ATMS is used to implement a novel thermal lens with a long focal length designed using transformation thermodynamics, and finally realize the ATMS with realistic materials and experimentally verify the performance of the designed long‐focus thermal lens (measured focal length of 19.8 mm) for remote heating/cooling. The proposed method expands the scope of the thermal conductivity and provides new pathways to realize unprecedented thermal effects with effective negative thermal conductivity, such as “thermal surface plasmon polaritons,” a thermal superlens, the thermal tunneling effect, and the thermal invisible gateway.
A long‐focus thermal lens with equivalent negative thermal conductivity is designed and experimentally realized to achieve a remote heating/cooling effect. The thermal lens consists of active thermal metasurfaces, which are constructed by p/n‐type semiconductor pairs driven by a DC power supply. The proposed method can also achieve other novel thermal effects, such as thermal superlens and thermal tunneling effects.
Special pure chalcogenide glass is the material of choice for many mid-infrared optical fibers and fiber lasers. In this paper, the thermo-optical lensing and laser-induced damage were studied in ...Ge35As10S55 and Ge20As22Se58 glasses and compared with the well-studied As2S3 glass. The thermal Z-scan technique with the quasi-CW Tm-doped fiber laser at 1908 nm was applied to study thermal lensing in chalcogenide glass. The laser-induced damage of various chalcogenide glasses was determined using the one-on-one procedure. The thermal nonlinear refractive index of the Ge35As10S55 and Ge20As22Se58 glasses was found to be lower than that of the As2S3 glass. The laser-induced damage threshold of the Ge20As22Se58 glass was determined to be higher than that of the Ge35As10S55 glass. The difference in the thermal damage threshold of the Ge35As10S55 and Ge20As22Se58 glasses and their lower value in comparison with the As2S3 glass were explained by a deviation from the stoichiometry of glass compositions and their tendency to crystallize.
Small-signal gain coefficient up to 1.2 per pass through active element is obtained experimentally in the laser multidisk amplifier of diode pumped solid state high peak and high average power laser ...system. The focal lengths of the thermal lenses are experimentally evaluated. Wavefront profiles are experimentally measured.
The temporal change of thermal lens effects has been measured for the development of high efficient laser system. Ytterbium phosphate glass was used due to its high saturation fluence property. A ...free running flashlamp pumped Ti:sapphire laser was developed for the high energy pump source. Pumping intensity on the glass surface exceeded 800 kW/cm
2
which is enough high for laser diode simulator. Shack-Hartmann wavefront sensor system was applied to measure the thermal lens effects on a highly pumped ytterbium glass oscillator. The temporal change of wavefront was successfully measured at high repetition rate of 100 Hz. The measured wavefront were expanded to Zernike coefficients. Cooling process for the focus coefficient agreed well with the prediction of unsteady one dimensional heat conduction.
Four organophosphorus compounds: azinphos-methyl, chlorpyrifos, malathion and malaoxon in aqueous solution were degraded by using a 125
W xenon parabolic lamp. Gas chromatography–mass spectrometry ...(GC–MS) was used to monitor the disappearance of starting compounds and formation of degradation products as a function of time. AChE-thermal lens spectrometric bioassay was employed to assess the toxicity of photoproducts. The photodegradation kinetics can be described by a first-order degradation curve
C
=
C
0e
−
kt
, resulting in the following half lives: 2.5
min for azinphos-methyl, 11.6
min for malathion, 13.3
min for chlorpyrifos and 45.5
min for malaoxon, under given experimental conditions. During the photoprocess several intermediates were identified by GC–MS suggesting the pathway of OP degradation. The oxidation of chlorpyrifos results in the formation of chlorpyrifos-oxon as the main identified photoproduct. In case of malathion and azinphos-methyl the corresponding oxon analogues were not detected. The formation of diethyl (dimethoxy-phosphoryl) succinate in traces was observed during photodegradation of malaoxon and malathion. Several other photoproducts including trimethyl phosphate esters, which are known to be AChE inhibitors and 1,2,3-benzotriazin-4(3H)-one as a member of triazine compounds were identified in photodegraded samples of malathion, malaoxon, and azinphos-methyl. Based on this, two main degradation pathways can be proposed, both result of the (P–S–C) bond cleavage taking place at the side of leaving group. The enhanced inhibition of AChE observed with the TLS bioassay during the initial 30
min of photodegradation in case of all four OPs, confirmed the formation of toxic intermediates. With the continuation of irradiation, the AChE inhibition decreased, indicating that the formed toxic compounds were further degraded to AChE non-inhibiting products. The presented results demonstrate the importance of toxicity monitoring during the degradation of OPs in processes of waste water remediation, before releasing it into the environment.
Hay una necesidad a nivel mundial de dispositivos compactos, de bajo costo y con alta sensibilidad y selectividad para monitoreo de aguas y análisis médicos y biológicos. La mayoría de los equipos ...del mercado adecuados para este tipo de aplicaciones son de dimensiones grandes y/o costos excesivos. Otro tipo de métodos requieren pre-tratamientos de las muestras haciendo que el análisis consuma mucho tiempo. En este trabajo se muestra el diseño de un sistema de lente térmica compacto y de bajo costo para monitoreo de aguas. El dispositivo consta de dos láseres compactos (punteros) con longitudes de onda de excitación de 405nm y 532 nm, modulados a baja frecuencia (4 y 7 Hz respectivamente), lo cual permite una medición diferencial en tiempo real. Además, posee un diodo rojo como haz de prueba cuyo haz atraviesa la muestra en forma colineal con los haces de excitación y una pequeña fracción de su luz es colectada por una fibra óptica de 200 μm, que la guía a un fotodiodo. La señal del detector es digitalizada por una placa Arduino y enviada a una PC para ser analizada. El procesamiento se realiza en tiempo real aplicando una transformada rápida de Fourier para diferenciar las señales provenientes de ambas fuentes de excitación. Se implementó un sistema de inyección en flujo que permite agilizar las mediciones. En este trabajo se muestra el funcionamiento del sistema haciendo uso de colorantes de baja toxicidad.
In this study, we experimentally investigated the shape dependent thermal and nonlinear optical properties of water stable ZnO nanostructures. It is important to note that morphology plays a ...significant role in determining thermo-optic properties of ZnO. The thermal conductivity of colloidal ZnO was measured using a dual beam collinear thermal lens technique. The result shows a 23% enhancement in thermal conductivity of ZnO nanofluid compared to that of base fluid water. The nanofluid with nonspherical ZnOnanoparticles exhibit greater thermal diffusivity than a fluid with spherical nanoparticles. This enhancement in thermal conductivity was explained using the Hamilton – Crosser model based on the formation of nanolayer and interfacial thermal resistance. The third-order nonlinear optical susceptibility and optical limiting properties were investigated using a single beam Z scan technique. All samples showed two photon absorption and a negative nonlinear refractive index which varied with the nanoparticle morphology. Higher dimensional structures showed better optical nonlinearity due to their large surface area, photon scattering and exciton oscillator strength. The Z scan results reveal an increment of three orders of magnitude in third-order susceptibility for the nanoparticles compared to that of bulk ZnO. The nanofluid also exhibits a good optical limiting behaviour. The findings suggest that ZnO nanostructures can be considered as promising candidates for future optoelectronic devices.
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