Physics and Astronomy

Visual optics

Optics of the human visual system, the influence of various factors on image quality, development of new methods to assess visual function.

Gunta Krūmiņa
(gunta.krumina@lu.lv; +371 67033945; 
https://www.fmof.lu.lv/en/about/about-faculty/department-of-optometry-and-vision-science/)

Eye movement analysis

Using eye movement analysis to study various brain processes. Evaluation of eye movement using manual, paper-based tests (NSUCO, DEM, etc.) and eye-trackers (mainly video-oculographs). Research can be carried out both individually and in collaboration with specialists from other fields.

Ilze Ceple
(ilze.ceple@lu.lv; +371 29630307; 
https://www.fmof.lu.lv/en/about/about-faculty/department-of-optometry-and-vision-science/)

Management of refractive errors

Refractive errors examination includes objective methods (retinoscopy and autorefractomy) and subjective testing of visual acuity, eye refraction, binocular and accommodation functions. Prescribing refractive correction is based on different objective and subjective measurements, as well as patient history and the progress of visual examination. 

Ilze Ceple
(ilze.ceple@lu.lv; +371 29630307; 
https://www.fmof.lu.lv/en/about/about-faculty/department-of-optometry-and-vision-science/)

Skin imaging

Application of skin imaging technologies to various clinical applications, including dermatology, hematology, and intensive care. The selection of the most appropriate technology for a specific application, as well as data acquisition, analysis, and interpretation of results.

Inga Saknīte
(inga.saknite@lu.lv; +371 29162679; 
https://www.linkedin.com/in/ingasaknite/; https://www.asi.lu.lv/en/)

Clinical studies

Conducting and leading clinical studies, and analyzing data with various methods, including biostatistical methods.

Inga Saknīte
(inga.saknite@lu.lv; +371 29162679; 
https://www.linkedin.com/in/ingasaknite/; https://www.asi.lu.lv/en/)

Reflectance confocal microscopy

Work with reflectance confocal microscopy data acquisition, analysis, and interpretation of results for noninvasive visualization of human skin. 

Inga Saknīte
(inga.saknite@lu.lv; +371 29162679; 
https://www.linkedin.com/in/ingasaknite/; https://www.asi.lu.lv/en/)

Spectral imaging

Work with spectral imaging data acquisition, analysis, and interpretation of results for noninvasive visualization of human skin.

Inga Saknīte
(inga.saknite@lu.lv; +371 29162679; 
https://www.linkedin.com/in/ingasaknite/; https://www.asi.lu.lv/en)

Multispectral skin image processing

Multispectral skin image processing. Parameters such as diffuse reflectance intensity, photobleaching speed, chromophore concentration and other parameters are extracted from the images. The images can also be combined to create parameter maps, they can be used with machine learning algorithms etc.

Emīlija Vija Ploriņa
(plorina@lu.lv; https://www.asi.lu.lv/en/)

The principle and practical application of iseikonic lenses

Study of aniseikonia, aniseikonia caused by external and internal factors, comparison of its assessment methods. Application of iseiconic lenses in the diagnostic and correction of aniseikonia.

Aiga Švede
(aiga.svede@lu.lv; +371 29181176; 
https://www.fmof.lu.lv/en/about/about-faculty/department-of-optometry-and-vision-science/)

Mercury concentration measurements in the air and environmental artefacts

Use of an atomic absorption spectrometer with Zeeman background correction for mercury concentration measurements in air and various liquid and solid environmental samples, such as natural waters, sediments, peat, eggshells and bird feathers. Use of cold-vapour AAS for mercury concentration measurements in water, solid samples are analysed using equipment for thermal combustion.  

Anda Ābola
(anda.abola@lu.lv; +371 26333007; https://www.asi.lu.lv/en/)

Spectral studies of light sources

Spectral studies with several spectrometers of different spectral resolutions to measure the radiation of such light sources as high-frequency electrodeless (HFEDLs) and hollow cathode lamps. Analysis of the recorded spectra to investigate the characteristics of light sources, and do low-temperature plasma diagnostics, for example, determination of the temperature of plasma components. Work with HFEDLs, including gathering information to optimize said light sources, the interaction between the quartz glass surface and plasma, and the use of UV radiation for disinfection.

Anda Ābola
(anda.abola@lu.lv; +371 26333007; https://www.asi.lu.lv/en/)

Whispering gallery mode resonator (WGMR) applications in sensors and telecommunications 

WGMR functionalization with a nanomaterial layer to improve optical properties, sensitivity or to create biosensors. With low power pumping, using a suitable WGMR geometry and material it is possible to generate an optical frequency comb that has potential for applications in telecommunications.

Inga Brice
(inga.brice@lu.lv; +371 26043617; 
https://www.asi.lu.lv/en/; https://www.researchgate.net/profile/Inga-Brice)

Multispectral imaging for skin diagnostics

Multispectral imaging of skin lesions using multispectral cameras (such as Nuance EX), self-made LED diode illumination device. Analysis of multispectral images, creation of diagnostic criteria considering the optical properties of skin chromophores and fluorophores (absorption, excitation, emission spectra). Application of artificial neural networks for classification of skin formations using multispectral images of skin formations. Previous work with most common skin lesions (e.g., melanoma, basal cell carcinoma, seborrheic keratosis, nevus, hemangioma, etc.) and diagnosis of rare diseases (Fäbri disease, Neurofibromatosis type 1, Darje, pseudoxanthoma).

Ilze Ļihačova
(ilze.lihacova@lu.lv; +371 29622569; https://www.asi.lu.lv/en/)

Aleksejs Ļihačovs
(aleksejs.lihacovs@lu.lv; +371 29331452; https://www.asi.lu.lv/en/)

Laser speckle imaging for the detection of bacterial and fungal colony growth and antibacterial resistance

Creation of a laser speckle system for determining the activity of microorganisms. Acquisition of laser speckle images in time, processing of image sets using sub-pixel correlation analysis method. Applications of the developed methods for determining the activity of microorganisms, counting colonies, improving the classical diffusion test method for faster assessment of antibacterial resistance in clinical conditions, as well as for the assessment and quantification of fungal growth.

Ilze Ļihačova
(ilze.lihacova@lu.lv; +371 29622569; https://www.asi.lu.lv/en/)

Aleksejs Ļihačovs
(aleksejs.lihacovs@lu.lv; +371 29331452; https://www.asi.lu.lv/en/)

Steady state and time resolved skin autofluorescence spectroscopy and imaging

Development of novel fluorescence based steady state and time-resolved spectroscopy techniques for in-vivo estimation of tissue fluorophore content and reactive oxygen species. Analysis and acquisition of tissue autofluorescence dynamics by means of fluorescence life-time and ultra-fast autofluorescence photobleaching detection. Clinical validation of the developed techniques for skin cancer diagnostics and therapy efficiency monitoring.

Aleksejs Ļihačovs
(aleksejs.lihacovs@lu.lv; +371 29331452; https://www.asi.lu.lv/en/)

Time-resolved spectroscopy. Fluorescence. Fluorescences lifetime.  Photons time-of-flight. Diffuse reflection.

The main area of research are in vivo and ex vivo biological samples fluorescence spectroscopy, fluorescence lifetime, and diffuse reflection with photon time-of-flight measurement methods. 

Vanesa Lukinsone 
(vanesa.lukinsone@lu.lv; https://www.asi.lu.lv/en/)

Optical measurements, color pigment analysis, biophotonics prototype devices, side-emitting optical fibers

In-depth expertise in classical and biomedical optics, photonics, fiber optics and laser physics.

Jānis Spīgulis
(janis.spigulis@lu.lv; +371 29485347; 
http://home.lu.lv/~spigulis/  https://www.asi.lu.lv/en/)

High-precision and sensitivity magnetic field measurements in one and three dimensions

Magnetic field measurements using specific point-like defects in a diamond crystal, nitrogen-vacancy (NV) centers. The magnetic field is determined using the quantum properties of these defects, so very small magnetic fields can be measured and their changes detected. The crystal lattice structure of diamond allows simultaneous measurement of both the strength and the direction of a magnetic field. Magnetic fields can be measured quickly, over a wide range, at different temperatures and pressures. The method used is spectroscopic, optically detected magnetic resonance and noise spectrum analysis.

Characterization of diamond crystals by their spectroscopic properties, detection of various defects, analysis of optical properties

Optically detected magnetic resonance (ODMR) measurements in various external magnetic fields. Analysis of the resulting spectra, determining the fluorescence intensity of a given diamond crystal and the presence of various defects. Analysis of the parameters of the NV ODMR signals of diamond crystals, e.g. from the perspective of their application to magnetic field measurements. Determination of the polarization of the nuclear spin of the NV centers in diamond at different external magnetic fields.

Two-dimensional imaging of magnetic field distribution

Using a diamond crystal, the ODMR method and a camera, it is possible to obtain a two-dimensional image of the magnetic field distribution produced by an object to be studied placed on the diamond crystal, it is possible to think of this as a magnetic field microscope. It is possible to analyse a variety of thin films and materials, magnetic particles and fine magnetic structures, magnetic bacteria. In addition, it is sometimes possible to see details in the magnetic image that are not visible in a conventional optical image. The typical dimensions of diamond crystals used are 3mm x 3mm x 0.5mm.

Characterization of diamond crystals by their relaxation times

Our magnetic field imaging device can also be used to characterize diamond crystals from the perspective of their relaxation times. It is also possible to perform experiments with various microwave and laser pulse sequences.

Annealing furnace

The annealing furnace can achieve temperatures up to 1100 °C and can be set to various heating programmes (temperature and time intervals). The furnace is used with a vacuum tube. The current application is the heating of diamond crystals so that the nitrogen atoms and lattice vacancies in the crystal lattice migrate to adjacent positions in the lattice when heated, thus forming nitrogen-vacancy centers. The furnace can also be used to heat something else as well.

Cryostat

We use the cryostat with liquid nitrogen, a vacuum is created at the tip. It can be placed in an electromagnet.

Registration of emission spectra with high resolution

High-resolution spectra from UV to near IR can be recorded with Fourier Transform spectrometer. Achievable resolution from 0.006 cm^-1 in IR to 0.03 in UV spectral range. 

Polarimeter

The polarimeter can measure the polarization of free-space optical beams in the wavelength range from 600 - 1080 nm, from laser powers as low as few nW up to 10 mW with beam width up to 3mm in diameter. Also the poalrization of an output of optical fibers can be measured via fiber connector. All normalized Stokes paramters can be extrated from the measurement.

Magnetic field sensors

The 3-axis magnetic field sensors can be used to measure magnetic fields up to 20 mT with 0.1 % accuracy or up to 0.1 mT (1 G) with 300 pT/√Hz sensitivity. The measurments of the magnetic field sensors ar based on the Hall effect and magntoresistance respectively.

Electromagnets in Helmhotz configuration for the creation of time-varying magnetic field and for the compensation of ambient field

The powerful electromagnets are used to  achieve fields as high as 1 T in one dimension. Aproximate field inhomogineity is less than 0.03%. Additionally 3-axis Helmholtz coils are available for control of magnetic fields (up to 10 mT ) in three orthogonal directions. These can also be used to compensate the ambient magnetic field.

Atomic reference cells

The absorbtion signals from the atomic reference cells (Cs, Rb, K, Na) can be used to calibrate optical equipment e.g. wavematers. The reference absorption spectra are produced by scanning the laser frequency around the corresponding atomic hyperfine transition.

Solution of inverse ill-posed tasks

Reconstructing a real line shape from a measured profile. For the solution of the ill-posed inverse task algorithm based on Tikhonov regularization is used. 

Diagnostic of high-frequency electrodeless light sources

Research focuses on a diagnostic of high-frequency electrodeless light sources for their use in atomic absorption spectroscopy. Special attention is devoted to line shape diagnostics for optically thin light sources filled with Tl, As, Hg, and other elements for their use in high-precision analyzers.

Analytical mathematical description of the interaction of electromagnetic radiation with atoms

Development of a mathematical model of the photon. Creating equations and finding solutions for various physical processes involving the photon. Analytical solutions for a specific electromagnetic field (e.g. half-period pulses) interacting with Rydberg atoms.

Development of theoretical and numerical models for the interaction of electromagnetic radiation with atoms, molecules and nanoparticles

Development of theoretical and numerical models for quantum and nonlinear optics with Rydberg-state atoms: calculations of dipole-dipole interaction and dipole blockade radius, Rydberg atom localization using spatially dependent fields and light vortices. Development of theoretical and numerical models for Electromagnetically Induced Grating with spatially dependent fields and light vortices. Development of theoretical and numerical models for dynamic quantum control of atomic and molecular optics processes: Landau-Zenner schemes, quantum control using the Autler-Townes effect. Theoretical  and numerical calculations for the impact of ionizing radiation on amino acids. Theoretical and numerical calculations of optical properties of ZnO nanoparticles.

Optimization of combustion processes, prevention of deposits

Analysis and visualization of various combustion processes and chemical reactions. Experience in conducting research on biomass gasification equipment, hydrochloric acid regeneration furnaces, etc., eliminating the shortcomings of this technological equipment, minimizing the formation of precipitation, improving the technical parameters of the equipment.

Cleaner and more efficient heat energy production

Electrical control of granulated biomass gasification, combustion and heat generation processes. The licensed technology is based on a detailed study of the effects of the interaction of an electric field and a flame whirl, which confirms that the effect of an electric field intensifies the thermal decomposition of granular biomass and the formation of volatile compounds, contributing to faster ignition of volatile compounds and their more complete combustion.

Development of liquid metal pumps, stirrers and dispensers

Development of equipment for the transportation of liquid metals for various stages of metallurgical processes for both scientific and industrial purposes. Extensive experience in the research and development of equipment of various scales for the transport of liquid metals, in which the magnetic field for the transport of metals is created by both rotating systems with permanent magnets and induction coils. This section also offers numerical models and calculations, as well as measurements of physical parameters such as fluid flow and temperature.

Design of astrogeodetic instruments and control & data processing software for them

Development of instrumentation design; configuration of included electronic and optical component, development of control and data processing software.