Millimeter Research Articles

A Flexible and Wearable Photodetector Enabling Ultra-Broadband Imaging from Ultraviolet to Millimeter-Wave Regimes.

Flexible and miniaturized photodetectors, offering a fast response across the ultraviolet (UV) to millimeter (MM) wave spectrum, are crucial for applications like healthcare monitoring and wearable optoelectronics. Despite their potential, developing such photodetectors faces challenges due to the lack of suitable materials and operational mechanisms. Here, the study proposes a flexible photodetector composed of a monolayer graphene connected by two distinct metal electrodes. Through the photothermoelectric effect, these asymmetric electrodes induce electron flow within the graphene channel upon electromagnetic wave illumination, resulting in a compact device with ultra-broadband and rapid photoresponse. The devices, with footprints ranging from 3 × 20 µm2 to 50 × 20 µm2, operate across a spectrum from 325nm (UV) to 1.19mm (MM) wave. They demonstrate a responsivity (RV) of up to 396.4 ± 5.1mVW-1, a noise-equivalent power (NEP) of 8.6 ± 0.1 nW Hz- 0.5, and a response time as small as 0.8 ± 0.1ms. This device facilitates direct imaging of shielded objects and material differentiation under simulated human body-wearing conditions. The straightforward device architecture, aligned with its ultra-broadband operational frequency range, is anticipated to hold significant implications for the development of miniaturized, wearable, and portable photodetectors.

Активно-пасивний імпульсно-шумовий радар діапазону 3мм та результати його попередніх випробувань

The subject of this manuscript is broadband noise signals and systems. The aim of this research is to show the results of a modern active-passive 3-mm waveband system consisting of a noise-pulsed radar and a radiometer. Noise radar systems (NRS) based on broadband signals are characterized by high resolution, accuracy, and information content when performing unambiguous measurements of the range and speed of targets, as well as increased electromagnetic compatibility and noise immunity. These distinctive features of NRS determine the relevance of their construction for practical tasks of short- and medium-range radar. Additional opportunities for ensuring secrecy, reliability of detection of objects, and their tracking are provided by the combination of active and passive location modes in conjunction with advancement to the short-wave part of the millimeter (MM) wave band (WB). The most important characteristic of any pulsed radar, which largely determines its potential for practical application, is the operating frequency, as well as the shape and width of the probing signal spectrum. The main idea of this work is to describe the construction scheme and the results of preliminary tests of the developed active-passive system in the 94 GHz band with a noisy 20–100 ns illumination pulse in the 5 GHz band. The obtained values of the energy potential of the system in the active location mode (-105 dB) and the achieved radiometer sensitivities in the passive mode (0.007K and 0.03K) make it possible to observe ground and air objects at a distance of several kilometres. Noted that the measured parameters of the radar, in the case of processing the received signal by pulse compression methods, make it possible to count on ensuring the resolution of targets in range at the level of 10-15 cm. A multiple (more than an order of magnitude) decrease in the interference fluctuations of the received signal, which is due to the facet nature of the backscattering of targets, has experimentally demonstrated using a noise probing pulse compared to a single-frequency pulse. The methods for further work on the development and practical application of the constructed measuring system are outlined.

Minimally Equicorrelated MIMO Modelling for NLOS MM Wave Performance Improvement

The 5G physical layer has evolved rapidly. With transmissions at 28, 38, and 72 GHz, millimeter (MM) wave communications are at the core of it. Such links provide improved data rates to an increased number of users availing around 20 GHz of free spectrum. Directional arrays in multiple-input multiple-output (MIMO) setups facilitate beamsteered transmissions. Maximal ratio combining (MRC) receivers aid MM wave signaling and link metrics are analyzed in terms of antenna correlations. The system model is evaluated assuming a short range, non-line-of-sight (NLOS) MM wave user under independently correlated, Rayleigh conditions. This paper showcases analytical closed form expressions for received signal, output signal- to-noise ratio (SNR), line-of-sight (LOS), probability density function (PDF), and NLOS average capacity of the proposed MM wave link. The derivations exhibit capacity alterations with transceiver correlations. MM wave correlation matrices have unique dependency on steering vectors or corresponding transmission angles. This does not apply to millimeter wave.

Study of the Effect of Low-Intensity Sub- and Millimeter Waves on the Induction of Adaptation Reactions in Experimental Burn

Burns are an actual problem of modern medicine. Oxidative stress, microcirculation, and hemostasis disorders are important links in the pathogenesis of burn disease. It is shown that these processes are significantly influenced by the point effect of low-intensity (LI) electromagnetic radiation (EMR) of the millimeter (MM) and submillimeter (subMM) ranges. However, the final opinion on the advantages of a particular range has not been formed. We have given a comparative assessment of the results of the effects of various frequency-energy parameters of microwaves on the indicators of adaptive reactions in rats under experimental thermal trauma and viscoelastic properties of blood in the case of burn disease.

Large Tunable 16-Tupled Millimeter Wave Generation Utilizing Optical Carrier Suppression With a Tunable Sideband Suppression Ratio

Coping up with the rising bandwidth demands for 5G ultra-high speed applications, utilizing millimeter (MM) wave spectrum for data transmission over the radio over a fiber-based system is the ideal approach. In this study, a highly conversant and spectrally pure photonic generation of a 16-tupled MM wave signal using a series-connected DD-MZM with a lower modulation index, a splitting ratio, and a wider tunable range is presented. A 160-GHz MM wave is generated through a double sideband optical carrier suppression technique having an optical sideband suppression ratio (OSSR) of 69 dB and a radio frequency sideband suppression ratio (RSSR) of 40 dB. However, the OSSR and the RSSR are tunable with values greater than 15 dB when the modulation index (M.I.) varies from 2.778 to 2.873, ±8° phase drift, and a 15-dB enhancement in the OSSR with a wider nonideal parameter variation range giving acceptable performance can be seen in the model as compared with previous research works.

Influence of low-intensity electromagnetic radiation of the millimeter range on the antioxidant system of juvenile Glycine max L. plants under osmotic stress

This study is devoted to identifying the adaptogenic effect of low-intensity electromagnetic radiation (EMR) of the millimeter (MM) range (wavelength – 7.1 mm, radiation frequency – 42.3 GHz, radiation power flux density – 0.1 mW/cm2) on the antioxidant system indicators of juvenile plants Glycine max L., cv. Apollo under osmotic stress caused by salinity. The stimulating effect of millimeter-wave electromagnetic radiation on the content of proline and carotenoids in Glycine max L. plants was revealed. The results obtained on the quantitative content of carotenoids showed that their content increased both in the normal conditions and under osmotic stress by an average of 1.2–1.8 times. An increased content of free proline in leaves was found in comparison with soybean roots under optimal conditions and under salinity.

Adaptogenic effect of low-intensity millimeter-wave electromagnetic radiation on Glycine Max L. under osmotic stress

This study is devoted to identification of the adaptogenic effect of low-intensity electromagnetic radiation (EMR) of the millimeter (MM) range (wavelength – 7.1 mm, radiation frequency – 42.3 GHz, radiation power flux density – 0.1 mW/cm2) on seed germination and growth processes of Glycine max L., cultivar Apollo under osmotic stress. The stimulating effect of millimeter-wave electromagnetic radiation on seed germination, morphometric parameters (height of the aerial part, length of the main root, accumulation of wet and dry matter mass) in plants of Glycine max L., cultivar Apollo has been revealed. Thus, it has been shown that pre-sowing irradiation with this physical factor increases the salt tolerance of Glycine max L., cv. Apollo. Germination energy and laboratory germination increase on average by 8–12% at simulated chloride salinity in the experimental variants, compared to the control ones. The positive effect of low-intensity EMR of the MM range on the morphometric parameters of Glycine max L. was established, while the shoot height significantly increased by 14%, the length of the main root – by 18%, the weight of the wet matter – by 5–13% in the experimental plants compared to control conditions of chloride salinization.

Millimeter (MM) wave and microwave frequency radiation produce deeply penetrating effects: the biology and the physics.

Millimeter wave (MM-wave) electromagnetic fields (EMFs) are predicted to not produce penetrating effects in the body. The electric but not magnetic part of MM-EMFs are almost completely absorbed within the outer 1mm of the body. Rodents are reported to have penetrating MM-wave impacts on the brain, the myocardium, liver, kidney and bone marrow. MM-waves produce electromagnetic sensitivity-like changes in rodent, frog and skate tissues. In humans, MM-waves have penetrating effects including impacts on the brain, producing EEG changes and other neurological/neuropsychiatric changes, increases in apparent electromagnetic hypersensitivity and produce changes on ulcers and cardiac activity. This review focuses on several issues required to understand penetrating effects of MM-waves and microwaves: 1. Electronically generated EMFs are coherent, producing much higher electrical and magnetic forces then do natural incoherent EMFs. 2. The fixed relationship between electrical and magnetic fields found in EMFs in a vacuum or highly permeable medium such as air, predicted by Maxwell's equations, breaks down in other materials. Specifically, MM-wave electrical fields are almost completely absorbed in the outer 1mm of the body due to the high dielectric constant of biological aqueous phases. However, the magnetic fields are very highly penetrating. 3. Time-varying magnetic fields have central roles in producing highly penetrating effects. The primary mechanism of EMF action is voltage-gated calcium channel (VGCC) activation with the EMFs acting via their forces on the voltage sensor,rather than by depolarization of the plasma membrane. Two distinct mechanisms, an indirect and a direct mechanism, are consistent with and predicted by the physics, to explain penetrating MM-wave VGCC activation via the voltage sensor. Time-varying coherent magnetic fields, as predicted by the Maxwell-Faraday version of Faraday's law of induction, can put forces on ions dissolved in aqueous phases deep within the body, regenerating coherent electric fields which activate the VGCC voltage sensor. In addition, time-varying magnetic fields can directly put forces on the 20 charges in the VGCC voltage sensor. There are three very important findings here which are rarely recognized in the EMF scientific literature: coherence of electronically generated EMFs; the key role of time-varying magnetic fields in generating highly penetrating effects; the key role of both modulating and pure EMF pulses in greatly increasing very short term high level time-variation of magnetic and electric fields. It is probable that genuine safety guidelines must keep nanosecond timescale-variation of coherent electric and magnetic fields below some maximum level in order to produce genuine safety. These findings have important implications with regard to 5G radiation.

Changes in skin microcirculation in response to low-intensity electromagnetic radiation of the millimeter range

The tissue microhemodynamics plays a significant role in a tissue homeostasis. Any pathological processes were changes in functioning of microhemodynamics. This is causes is significant interesting to safe methods for its correction. One of such methods is exposure to low-intensity electromagnetic radiation of the millimeter (MM) range, which has pronounced of biological activity. The aim of the work was to identify changes in the processes of microcirculation in human skin when exposed to a low-intensity EMR MM range (wavelength - 7.1 mm; power flux density - 0.1 mW/cm2). The study was conducted on 40 volunteer girls aged 18-20 years. The exposure of low-intensity MM radiation was carried out daily for 10 days with an exposure of 30 minutes on the area of biologically active area GI-4. Microcirculation indices were recorded by laser Doppler flowmetry both in the area of influence of MM radiation (contact point of registration) and in the symmetrical effect of the area (distant point) to detect local and systemic changes in tissue blood flow under the action of this physical factor. The results of the study revealed for the first time that when exposed to low-intensity MM radiation, local changes in tissue blood flow in the contact point area were observed, manifested in changes in myogenic and endothelial oscillatory activity, starting from the first sessions of exposure, which indicates a decrease in peripheral resistance of precapillary sphincters and an increase in secretory activity of microvascular endothelium; changes in neurogenic oscillations-starting from the third session, which is accompanied by a decrease in arteriolar resistance; changes in pulse fluctuations - during the last tenth session of exposure, which is an indication of an increase in arteriolar blood filling. These changes were maintained during the entire period of exposure to this physical factor. Systemic changes in microcirculation parameters at a distant symmetrical point during the course action of MM radiation were characterized by changes in the neurogenic oscillator component, starting from the third session of exposure, and changes in the amplitude of endothelial and pulse oscillations - during the tenth session.

Light-Controlled Polarization of MM-Waves with Photo-Excited Gratings in a Resonant Semiconductor Slab

We investigated photoconductive gratings in the resonant semiconductor layers as light-controlled polarizers for the millimeter (MM) waves. We compared the effects of strip-like, wire-like, and fin-like gratings excited by the red light and the IR radiation in Silicon wafers, respectively. The fin-like gratings are shown to be the preferred structures that can operate at the limited light intensity. The light-sensitive shift of maxima of transmitted power and polarizing efficiency towards the lower frequency band is observed. The effect makes photoconductive gratings and similar patterns potentially suitable for the design of light-controlled frequency-tuning and frequency-modulating components of resonant quasi-optical devices.

Proposal and performance analysis on the PDM microwave photonic link for the mm-wave signal with hybrid QAM-MPPM-RZ modulation

A polarization division multiplexed (PDM) microwave photonic link for the millimeter (MM)-wave signal with hybrid modulation scheme is proposed in this paper, which is based on the combination of quadrature amplitude modulation, multi-pulse pulse-position modulation and return to zero modulation (QAM-MPPM-RZ). In this scheme, the two orthogonal polarization states enable simultaneous transmission of four data flows, which can provide different services for users according to the data rate requirement. To generate hybrid QAM-MPPM-RZ mm-wave signal, the QAM mm-wave signal is directly modulated by MPPM-RZ signal without using digital signal processing (DSP) devices, which reduces the overhead of the encoding process. Then, the generated QAM-MPPM-RZ mm-wave signal is transmitted in PDM microwave photonic link based on SSB modulation. The sparsity characteristic of QAM-MPPM-RZ not only improves the power efficiency, but also decreases the degradation caused by the fiber chromatic dispersion. The simulation results show that, under the constraint of the same transmitted data rate, the PDM microwave photonic link with 50 GHz QAM-MPPM-RZ mm-wave signal achieves much lower levels of bit-error rate than ordinary 32-QAM. In addition, the increase of laser linewidth brings no additional impact to the proposed scheme.

Catching jetted tidal disruption events early in millimetre

Relativistic jets can form from at least some tidal disruption events (TDEs) of (sub-)stellar objects around supermassive black holes. We detect the millimeter (MM) emission of IGR J12580+0134 --- the nearest TDE known in the galaxy NGC 4845 at the distance of only 17 Mpc, based on Planck all-sky survey data. The data show significant flux jumps after the event, followed by substantial declines, in all six high frequency Planck bands from 100 GHz to 857 GHz. We further show that the evolution of the MM flux densities are well consistent with our model prediction from an off-axis jet, as was initially suggested from radio and X-ray observations. This detection represents the second TDE with MM detections; the other is Sw J1644+57, an on-axis jetted TDE at redshift of 0.35. Using the on- and off-axis jet models developed for these two TDEs as templates, we estimate the detection potential of similar events with the Large Millimeter Telescope (LMT) and the Atacama Large Millimeter/submillimeter Array (ALMA). Assuming an exposure of one hour, we find that the LMT (ALMA) can detect jetted TDEs up to redshifts $z\sim1$ (2), for a typical disrupted star mass of $\sim1$ M$_\odot$. The detection rates of on- and off-axis TDEs can be as high as $\sim0.6$ (13) and 10 (220) per year, respectively, for the LMT (ALMA). We briefly discuss how such observations, together with follow-up radio monitoring, may lead to major advances in understanding the jetted TDEs themselves and the ambient environment of the CNM.

Dielectric Properties of Biocompatible and Biodegradable Polycaprolone and Polylactide and Their Nanocomposites in the Millimeter Wave Band

Dielectric properties of biocompatible and biodegradable poly-ε-caprolone (PCL) and polylactide (PLA), as well as their nanocomposites, are measured in the millimeter (MM) wave band. It is found that the complex dielectric permittivity of PCL and its nanocomposites increases with temperature in the interval from 40 to 50℃, while that of PLA and its nanocomposites increases in the interval from 85 to 90℃. The samples of PLA with carbon nanotubes prepared with melamine show much lower absorption compared with the same samples prepared without melamine. The latter fact can be attributed to the formation of clusters of nanotubes in these samples.

INVESTIGATION OF QUASI-OPTICAL BESSEL-GAUSS RESONATOR AT MM- AND SUBMM-WAVELENGTHS

A research of a quasi-optical Bessel-Gauss resonator (QOBGR) at millimeter (MM) and submillimeter (SubMM) wave- bands is presented in this paper. The design is based on the quasi- optical theory and technique. The iterative Stratton-Chu formula (ISCF) algorithm is employed to analyze the output characteristics of the cavity, including the resonant modes, phases, power losses and phase shifts. Analysis of the results demonstrates that the present de- sign of the QOBGR can support zero order or any high order mode of the pseudo Bessel-Gauss beam. At the output plane the intensity distributions of these modes are modulated by a Gauss-shaped enve- lope, and their phase patterns have an approximate block-like proflle. Tolerance analysis for the designed QOBGR is also done. Lastly, a comparison of resonating modes is made between QOBR (quasi-optical Bessel resonator) and QOBGR when both are conflgured with the same geometric parameters.

Synthesis of Functional Materials Based on Electromagnetic Processing

Materials fabrication based on millimeter (MM)-wave and pulsed high current (SPS) heating processes have been reviewed and characteristics of these processes are discussed from the standpoints of the interaction between electromagnetic energy and solid materials. Capabilities of these processes in the fabrication of functional materials are indicated by exemplifying several successful results such as highly-strengthened or nano-structured alumina, highly thermal conductive AlN and preferentially oriented dense nano-structured anatase. In MM-wave heating process, the interactions between millimeter-wave and charged species in solid, such as ponderomotive force, have the important roles on the consolidation of powder materials, while atomistic mechanism in SPS heating process has not been explained well, though pulsed high current effect is important. Synthesis of pseudobinary T-Al-N (T: transition element) coatings by PVD process is also reviewed as an example of the processes assisted by electromagnetic energy. Hardness of the nitride coatings can be improved by dissolving AlN into TN and the formation of pseudobinary hard phase dissolved AlN is qualitatively explained by the pressure effect of energetic particle bombardment in PVD process. The experimental values of the maximum solubility of AlN into TN show good agreement with the values predicted by the band parameters method, indicating the importance of prediction based on electronic picture.

Standoff Detection Using Millimeter and Submillimeter Wave Spectroscopy

The millimeter (MM) wave and sub-MM wave (30-600 GHz) frequency band contains fundamental rotational and vibrational resonances of many molecular gases composed of carbon, nitrogen, oxygen, and sulphur. The high specificity of rotational spectra to organic molecules affords MM wave spectroscopy having potential use in remotely sensing atmospheric pollutants and the detection of airborne chemicals is important for arms control treaty verification, intelligence collection, and environmental monitoring. This paper considers the sensitivity requirements of radiofrequency receiver systems for measuring MM wave absorption/emission signatures. The significance of receiver sensitivity and material optical depth to sensing is highlighted. A background to the technology needed for sensing at MM and sub-MM wavelengths then provides the basis for a review of MM wave spectroscopy and its role on profiling the concentrations of trace polar molecules and ionized radicals in the high altitude atmosphere. The application of the MM wave spectroscopic technique in ambient conditions is then reviewed and the issues associated with developing the technique for standoff remote sensing is discussed.

Impact of the Collisional Plasma on the Propagation of Millimeter Waves

The plasma generated in the low-altitude atmosphere is of high collision frequencies. In this paper, the transmission coefficients of millimeter (MM) waves normally incident upon the plasma with high collision frequencies are calculated and analyzed. The experimental results of reflection and attenuation are presented for the eight-millimeter waves propagating through the plasma. Both the calculated experimental results indicate that the MM-waves concerned are attenuated significantly and reflected weakly, when propagating through the plasma of high collision frequencies.

Controlled dumping of pulses of laser radiation ranging from MIR to the MM by means of optical semiconductor switching

A simple method to produce sub-ns pulses of laser radiation with wavelength ranging from middle infrared (MIR) to millimeter (MM) is experimentally demonstrated. The system operates with a single OSS (optical semiconductor switching) driven by a ns Nd laser. Pulse control is produced by varying the distance of a mirror from an OSS used as a cavity dumping. The effectiveness of this sub-ns MM pulse generation is larger than the one observed in other schemes. Pulses with 500-ps FWHM and 15-W power were produced at 2.65 mm with a time compression compared to the 2-ns FWHM of the 1.06-μm driving laser.

Time stretching of 102-GHz millimeter waves using novel 1.55 μm polymer electrooptic modulator

Millimeter (MM)-wave signals at frequencies up to 102 GHz have been time stretched down to 11 GHz using a new wide-band traveling-wave polymer modulator. This is the first application of electrooptic modulators fabricated using the new polymer material PC-CLD, which has demonstrated good optical loss and high nonlinearity at 1.55 μm.

Millmeter Wave Aquametry

ABSTRACTSpecific advantage of millimeter (MM) wave aquametry is discussed. MM waves ensure better spatial resolution and better sensitivity to water than microwaves. MM waves are less sensitive to conducting impurities than microwaves, and MM waves can be used for water testing in media that are opaque to optical and infrared radiation. In the paper the water content measurement methods for some liquid and solid-state materials are described. Examples of devices for water control in crude oil, alcohol, powders used in metallurgy, paper, timber are considered. Usually it is possible to measure moisture content in real time (including in flow) with uncertainty less than 0.1%.