Functional brain network analysis is important for understanding the causes of neurological disorders and relevant brain mechanisms. Lately, functional near-infrared spectroscopy (fNIRS) yields outputs similar to the blood-oxygen-level-dependent signals of functional magnetic resonance imaging (fMRI), and numerous studies have been conducted on functional connectivity and causality using fMRI and fNIRS. Despite the existence of numerous analysis toolboxes for fNIRS, most of them are difficult to use because they involve numerous steps, coefficients, and related files. In this study, we developed a MATLAB toolbox called OptoNet, to analyze cortical networks in the brain for fNIRS. Given that OptoNet consists of a simple and intuitive graphical user interface, users can readily analyze the cortical networks of the brain for fNIRS signals. To evaluate the efficacy of the developed toolbox, the finger tapping task experiment—extensively used in brain functional activities and causal connectivity studies—was employed. The experiment was performed using the right and left hands, and both hands simultaneously, and the consequently elicited brain cortical network activity was analyzed using developed OptoNet.

We developed an optical cryostat with a sample-rotation unit for polarization-sensitive measurement in terahertz (THz) and infrared (IR) ranges. The cryostat, in combination with two metal-grid polarizers, provides full control of mutual orientation of the sample’s crystallographic axes and the light polarization plane. Importantly, this control is realized in-situ, i.e., during the sample cooling–heating cycle. To demonstrate the abilities of the developed cryostat, we used it in combination with a laboratory-made THz time-domain spectrometer, for polarization-sensitive measurements of an orthoferrite (YFeO₃) in the range of 5 to 50  cm^−  1. These measurements revealed strong angular dependence of the sample transmission. The developed cryostat is capable for solving numerous demanding problems of THz and IR spectroscopy in condensed matter physics and materials science, biophysics, chemical, and pharmaceutical sciences.

Infrared thermography can be used as a measuring technology that records the thermal reaction of body to an external effect. In this case, the external impact is low-intensity optical radiation (LOR). Temperature is measured using a short-wave (1.5 to 5.1  μm) infrared camera. It is known that LOR produces a therapeutic effect. At the same time, the reason for this action remains unclear. The effect of LOR of the human forearm with λ  =  640  ±  10  nm with dose 5.04, 8.4  J  /  cm² on the temperature of the palm of the irradiated hand is studied. Temperature measurements continue during and after irradiation for 20 min. To interpret the results, a change in the temperature of the palm of volunteers who drank hot water is also investigated. It is found that the temperature after exposure to LOR is definitely established at a new level, depending on the radiation dose. Changes in surface temperature are associated with stimulation of blood flow. Literature data suggest that the observed response of the body to radiation may be caused by the work of the vascular relaxation factor, photoreactivation of superoxide dismutase, and the death of blood cells during irradiation.

We analyze the pumping of the graphene-based laser heterostructures by infrared radiation using the numerical model. To enable the injection of sufficiently cooled carriers into the graphene layer (GL) leading to the interband population inversion, we propose to use the graded-gap black-P_xAs_{1  −  x} absorption-cooling layers. Our calculations are based on the thermodiffusion-drift carrier transport model. We demonstrate that the proposed optical pumping method can provide an efficient injection of the cool electron–hole plasma into the GL and the interband population inversion in the GL. Since the energy gap in b-As layer can be smaller than the energy of optical phonons in the GL, the injected electron–hole plasma can be additionally cooled down to the temperatures lower than the lattice temperature. This promotes a stronger population inversion that is beneficial for realization of the GL-based optically pumped terahertz and far-infrared laser, plasmon emitters, and the superluminescent downconverters. We also compare the efficiency of optical pumping through the graded-gap and uniform absorbing-cooling layers.

Mesenchymal stem cells (MSCs) represent a significant interest for cell therapy applications and, being primary cells, undergo gradual aging in culture. We studied the effects of low-intensity infrared laser irradiation during aging of MSCs in culture. Both young and aged MSCs respond to low irradiation doses (0.17  J  /  cm²) by growth activation and to middle doses (2.1  J  /  cm²) by growth retardation. Aged cells demonstrate a relatively higher growth response to low doses, but they are significantly more susceptible to deleterious effects of middle doses compared to young cells. Studies of MSC aging during long-term culture under hypoxia conditions demonstrate that low-dose irradiation of MSCs every 2 days in culture substantially increases the number of population doublings, compared to the control group. In addition, irradiated cells persisted in culture for two passages (4 days) longer than their control counterparts. However, irradiated cells did not proliferate more rapidly if irradiation was omitted. We conclude that growth responses of young and aged murine MSCs to infrared laser irradiation differ significantly and that regular irradiation affects MSC aging in culture but does not result in a bonafide retardation of aging process.

This review highlights recent and novel trends focused on metallic (plasmonic) and dielectric metasurfaces in photoconductive terahertz (THz) devices. We demonstrate the great potential of its applications in the field of THz science and technology, nevertheless indicating some limitations and technological issues. From the state-of-the-art, the metasurfaces are, by far, able to force out previous approaches like photonic crystals and are capable of significantly increasing the performance of contemporary photoconductive devices operating at THz frequencies.