Advanced Electromagnetic Metamaterials for Temperature Sensing Applications

Metamaterials with novel properties have excited much research attention in the past several decades. Many applications have been proposed and developed for the reported metamaterials in various engineering areas. Specifically, for the resonant-type metamaterials with narrow resonance line width and strong resonance strength, the resonant frequency and strength are highly depended on the changings of meta-atom structure and/or substrate media properties induced by the environment physical or chemistry parameters varying. Therefore, physical or chemistry sensing applications for the resonant-type metamaterial units or arrays are developed in recent years. In this mini review, to help the researchers in those fields to catch up with the newly research advances, we would like to summarize the recently reported high-performance metamaterial-inspired sensing applications, especially the temperature sensing applications, based on different kinds of metamaterials. Importantly, by analyzing the advantages and disadvantages of several conventional metamaterial units, the newly proposed high quality-factor metamaterial units are discussed for high-precision sensing applications, in terms of the sensitivity and resolution. This mini review can guide researchers in the area of metamaterial-inspired sensors to find some new design routes for high-precision sensing.

Полностью оптический магнитометрический датчик для задач магнитоэнцефалографии и томографии сверхслабого поля

A version of the scheme of an atomic cesium vapour magnetometric sensor using magnetic resonance excitation by modulated radiation transverse to the magnetic field of hyperfine optical pumping is proposed and experimentally studied. It is shown that when using a cell with a volume of 0.125 cm3, the variational sensitivity of the sensor, estimated from the ratio of the steepness of the signal at the center of the magnetic resonance to the shot noise of the detecting radiation, reaches a level of less than 10 fT/Hz1/2 in the frequency band determined by the magnetic resonance line width (of the order of 800 Hz). The sensor, which does not use and does not emit resonant radio-frequency fields, is designed to operate in magnetoencephalographic complexes. Possible ways to increase the frequency response of the circuit for detecting relatively fast (~ 4.2 kHz in a field of 0.1 mT) proton magnetic moment precession signals in promising ultralow field tomography schemes are considered.

Проекционный спиновый шум в оптических квантовых датчиках на тепловых атомах

The paper theoretically and experimentally investigates the fundamental limitations imposed by spin (or atomic) quantum projection noise on the sensitivity of optical quantum sensors based on thermal atoms (this class of devices includes frequency standards, magnetometers, and gyroscopes using optical detection of electron paramagnetic resonance). The effect of increasing the rms amplitude of the projection noise in the magnetometric scheme under the influence of strong optical pumping is demonstrated, its explanation is proposed and experimentally tested - it is shown that in a wide range of pump intensities this effect is explained by the invariance of the projection noise integral power with respect to the magnetic resonance line width. An experimental study of the parameters of projection noise in a magnetometric quantum sensor was carried out, recommendations were given for optimizing the sensor parameters.

Infrared Propagating Electromagnetic Surface Waves Excited by Induction

Propagating inhomogeneous electromagnetic waves called surface plasmon polaritons (SPPs) can be excited by free-space beams on corrugated conducting surfaces at resonance angles determined by corrugation period, permittivity, and optical frequency. SPPs are coupled to and co-propagate with surface charge displacements. Complete electrical isolation of individual conducting corrugations prevents the charge displacement necessary to sustain an SPP, such that excitation resonances of traveling SPPs are absent. However, SPPs can be excited via electric induction if a smooth conducting surface exists below and nearby the isolated conducting corrugations. The dependence of SPP excitation resonances on that separation is experimentally investigated here at long-wave infrared wavelengths. We find that excitation resonances for traveling SPPs broaden and disappear as the dielectric’s physical thickness is increased beyond ~1% of the free-space wavelength. The resonance line width increases with refractive index and optical thickness of the dielectric.