Pub Date : 2023-11-26DOI: 10.3952/physics.2023.63.3.7
B. Škėlaitė, V. Jakštas, M. Treideris, A. Bičiūnas, K. Ikamas, R. Butkutė, I. Grigelionis
In this paper, the thermal emission from the n-GaAs/GaAs structure equipped with the Ti/Au metasurface is being investigated in the terahertz region. The metacell shape was chosen to be of heraldic origin, that is either the Ukrainian Trident or the Lithuanian Columns of Gediminids. The experiments were performed using far-infrared Fourier spectroscopy, where the heated sample served as the source of THz radiation. The optical properties of such structures were simulated using the rigorous coupled wave analysis method in order to explain the origin of experimentally observed spectral features. The deconstruction of the simulated spectra was also performed by simulating the properties of simplified metacells which constitute the metacells of the heraldic symbols investigated here. The spectral analysis suggests the similarity between the investigated symbols, which is also reviewed from the historical point of view.
{"title":"Terahercų emisijos spektroskopija pavidalų panašumui tirti: Ukrainos ir Lietuvos simbolių nagrinėjimas","authors":"B. Škėlaitė, V. Jakštas, M. Treideris, A. Bičiūnas, K. Ikamas, R. Butkutė, I. Grigelionis","doi":"10.3952/physics.2023.63.3.7","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.7","url":null,"abstract":"In this paper, the thermal emission from the n-GaAs/GaAs structure equipped with the Ti/Au metasurface is being investigated in the terahertz region. The metacell shape was chosen to be of heraldic origin, that is either the Ukrainian Trident or the Lithuanian Columns of Gediminids. The experiments were performed using far-infrared Fourier spectroscopy, where the heated sample served as the source of THz radiation. The optical properties of such structures were simulated using the rigorous coupled wave analysis method in order to explain the origin of experimentally observed spectral features. The deconstruction of the simulated spectra was also performed by simulating the properties of simplified metacells which constitute the metacells of the heraldic symbols investigated here. The spectral analysis suggests the similarity between the investigated symbols, which is also reviewed from the historical point of view.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"29 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139234899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-26DOI: 10.3952/physics.2023.63.3.8
V. Abramova, S. Abramov, V. Lukin, I. Grigelionis, L. Minkevičius, G. Valušis
The paper discusses issues of digital processing of terahertz images. It is shown that despite the improvement of the hardware part of imaging setups, the acquired images still often have a low resolution and suffer from noise and blurring effects. Thus, to improve their visual quality, it is advisable to use special digital processing methods. While some progress has already been made in terms of denoising of terahertz images, the research of their deblurring is only at the very early stage. Therefore, this paper attempts to analyze the properties of blur functions for real terahertz images to further use them while designing a corresponding deblurring technique. For this purpose, the phase-only image method has been used. A study of blur properties for the three most common blur types (defocus, motion and Gaussian blur) has shown that for test images they can be distinguished and their main parameters can be assessed. However, the application of this method to real terahertz images has shown that the blur characteristics in them are very different from the ones obtained for modelled examples. The real blur demonstrates a quite complex behaviour and estimating its kernel requires additional research.
{"title":"Investigation of blur kernel of terahertz images","authors":"V. Abramova, S. Abramov, V. Lukin, I. Grigelionis, L. Minkevičius, G. Valušis","doi":"10.3952/physics.2023.63.3.8","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.8","url":null,"abstract":"The paper discusses issues of digital processing of terahertz images. It is shown that despite the improvement of the hardware part of imaging setups, the acquired images still often have a low resolution and suffer from noise and blurring effects. Thus, to improve their visual quality, it is advisable to use special digital processing methods. While some progress has already been made in terms of denoising of terahertz images, the research of their deblurring is only at the very early stage. Therefore, this paper attempts to analyze the properties of blur functions for real terahertz images to further use them while designing a corresponding deblurring technique. For this purpose, the phase-only image method has been used. A study of blur properties for the three most common blur types (defocus, motion and Gaussian blur) has shown that for test images they can be distinguished and their main parameters can be assessed. However, the application of this method to real terahertz images has shown that the blur characteristics in them are very different from the ones obtained for modelled examples. The real blur demonstrates a quite complex behaviour and estimating its kernel requires additional research.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"16 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139235338","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-26DOI: 10.3952/physics.2023.63.3.2
P. Komorowski, M. Kaluza, S. Surma, A. Siemion
In this paper, we demonstrate the manufacturing of diffractive optics for frequencies as high as 1 THz using a relatively simple and cost-effective fused deposition modelling (FDM) 3D printing technique. Four diffractive lenses were designed and manufactured from the cyclic olefin copolymer (COC). Fabrication of diffractive lenses for such high frequencies was possible due to an unusually small nozzle, refined printing procedures and a very transparent material. For the two of the manufactured lenses, more than twofold improvement in focusing efficiency has been shown in a direct comparison with their refractive counterparts. Moreover, the other two elements demonstrated the feasibility of lenses with very small f-numbers (0.95 and 0.63) with this technique.
{"title":"3D printed diffractive lenses operating at 1 THz","authors":"P. Komorowski, M. Kaluza, S. Surma, A. Siemion","doi":"10.3952/physics.2023.63.3.2","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.2","url":null,"abstract":"In this paper, we demonstrate the manufacturing of diffractive optics for frequencies as high as 1 THz using a relatively simple and cost-effective fused deposition modelling (FDM) 3D printing technique. Four diffractive lenses were designed and manufactured from the cyclic olefin copolymer (COC). Fabrication of diffractive lenses for such high frequencies was possible due to an unusually small nozzle, refined printing procedures and a very transparent material. For the two of the manufactured lenses, more than twofold improvement in focusing efficiency has been shown in a direct comparison with their refractive counterparts. Moreover, the other two elements demonstrated the feasibility of lenses with very small f-numbers (0.95 and 0.63) with this technique.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"18 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139235402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-26DOI: 10.3952/physics.2023.63.3.3
A. Kamarauskas, L. Staišiūnas, D. Seliuta, G. Šlekas, Ž. Kancleris
Here we propose a voltage-controlled Fabry–Perot modulator made of two overlapping graphene sheets separated by a hafnium oxide layer, manufactured on a silicon substrate. The applied voltage shifts the Fermi level in both layers thus changing the total surface conductivity. This in turn changes the optical parameters of the system. Due to the architecture of the modulator, ≈50% of THz power is absorbed and the applied voltage controls the ratio between the reflection and transmittance. At the resonance frequency of 414 GHz, the transmission through the Fabry–Perot modulator can be doubly reduced in a voltage range of –1.5 to 10 V. In DC measurements, it is revealed that the electrical properties of graphene sheets dramatically depend on the technological process. The proposed multilayer structure can be manufactured on any THz-transparent substrate, compatible with photolithography and atomic layer deposition (ALD) processes.Voltage-controlled surface conductivity could find its application in sensing or modulation of electromagnetic waves.
在这里，我们提出了一种电压控制法布里-珀罗调制器，它由两片重叠的石墨烯片组成，中间用氧化铪层隔开，在硅衬底上制造而成。外加电压会改变两层石墨烯的费米级，从而改变总表面电导率。这反过来又改变了系统的光学参数。由于调制器的结构，50% 的太赫兹功率被吸收，外加电压控制着反射和透射之间的比率。在共振频率为 414 GHz 时，通过法布里-珀罗调制器的传输可在 -1.5 至 10 V 的电压范围内成倍降低。所提出的多层结构可以在任何太赫兹透明基底上制造，与光刻和原子层沉积（ALD）工艺兼容。
{"title":"Voltage controlled Fabry–Perot modulator","authors":"A. Kamarauskas, L. Staišiūnas, D. Seliuta, G. Šlekas, Ž. Kancleris","doi":"10.3952/physics.2023.63.3.3","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.3","url":null,"abstract":"Here we propose a voltage-controlled Fabry–Perot modulator made of two overlapping graphene sheets separated by a hafnium oxide layer, manufactured on a silicon substrate. The applied voltage shifts the Fermi level in both layers thus changing the total surface conductivity. This in turn changes the optical parameters of the system. Due to the architecture of the modulator, ≈50% of THz power is absorbed and the applied voltage controls the ratio between the reflection and transmittance. At the resonance frequency of 414 GHz, the transmission through the Fabry–Perot modulator can be doubly reduced in a voltage range of –1.5 to 10 V. In DC measurements, it is revealed that the electrical properties of graphene sheets dramatically depend on the technological process. The proposed multilayer structure can be manufactured on any THz-transparent substrate, compatible with photolithography and atomic layer deposition (ALD) processes.Voltage-controlled surface conductivity could find its application in sensing or modulation of electromagnetic waves.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"26 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139235811","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-26DOI: 10.3952/physics.2023.63.3.4
G. Kontenis, D. Gailevičius, V. Jukna, K. Staliūnas
Non-Gaussian spatial intensity distribution beams used in laser micro- and nano-machining find many applications. For instance, Bessel beams, having a small diameter and a very long focal zone, allow the fabrication of high aspect ratio modifications in transparent materials. Higher-order Laguerre–Gauss modes are used in particle manipulation and even for multiplexing in optical communication. The temporal intensity distribution of a pulse is mostly overlooked or fixed to Gaussian shape distribution. However, pulse-shaped beams could improve the same fields of particle manipulation as optical traps, or the laser manufacturing. In this paper, we demonstrate a method of constructing a helical spatiotemporal intensity distribution beam the rotation of which in time can be varied. We demonstrate the analytical and numerical results and show an experimental realization of such a structure.
{"title":"Chirped LG modes interference formed chiral beams","authors":"G. Kontenis, D. Gailevičius, V. Jukna, K. Staliūnas","doi":"10.3952/physics.2023.63.3.4","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.4","url":null,"abstract":"Non-Gaussian spatial intensity distribution beams used in laser micro- and nano-machining find many applications. For instance, Bessel beams, having a small diameter and a very long focal zone, allow the fabrication of high aspect ratio modifications in transparent materials. Higher-order Laguerre–Gauss modes are used in particle manipulation and even for multiplexing in optical communication. The temporal intensity distribution of a pulse is mostly overlooked or fixed to Gaussian shape distribution. However, pulse-shaped beams could improve the same fields of particle manipulation as optical traps, or the laser manufacturing. In this paper, we demonstrate a method of constructing a helical spatiotemporal intensity distribution beam the rotation of which in time can be varied. We demonstrate the analytical and numerical results and show an experimental realization of such a structure.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"22 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139235700","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-24DOI: 10.3952/physics.2023.63.3.1
S. Mundrys, S. Orlov, P. Kizevičius, L. Minkevičius, G. Valušis
High numerical apertures lead to an appearance of distortions in a single-shot image, which make obtaining images troublesome if not impossible. These obstacles can be overcome in single-pixel imaging, where different strategies lead to inspection of objects with a good resolution, contrast and brightness. Recent advances in flat photonic elements have enabled the creation of compact nonparaxial imaging systems, which are especially promising in the THz range of wavelengths, bringing advances to such fields as communication, material inspection and spectroscopy. In this work, we dive into the problematics of single-pixel imaging: we introduce an object sample, which we use to investigate the resolution, contrast and brightness of the classical two-lens imaging setup. We evaluate the nonparaxial imaging of the sample and report that the conditions for the best contrast and the best brightness are decoupled in nonparaxial single pixel imaging. To overcome this hurdle, we use two integral image quality assessment techniques from computational imaging theory and estimate the quality of the image in a virtual numerical THz imaging scenario. The localized mean square error metric did not cause additional constraints to the quality of the image, whereas the global mean square error has restricted the range of possible imaging setups. Thus, the computational integral image quality assessment techniques back up the main claim of this study that in the single-pixel imaging the resolution is decoupled from the image brightness.
{"title":"On evaluation of image quality in nonparaxial single-pixel imaging","authors":"S. Mundrys, S. Orlov, P. Kizevičius, L. Minkevičius, G. Valušis","doi":"10.3952/physics.2023.63.3.1","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.1","url":null,"abstract":"High numerical apertures lead to an appearance of distortions in a single-shot image, which make obtaining images troublesome if not impossible. These obstacles can be overcome in single-pixel imaging, where different strategies lead to inspection of objects with a good resolution, contrast and brightness. Recent advances in flat photonic elements have enabled the creation of compact nonparaxial imaging systems, which are especially promising in the THz range of wavelengths, bringing advances to such fields as communication, material inspection and spectroscopy. In this work, we dive into the problematics of single-pixel imaging: we introduce an object sample, which we use to investigate the resolution, contrast and brightness of the classical two-lens imaging setup. We evaluate the nonparaxial imaging of the sample and report that the conditions for the best contrast and the best brightness are decoupled in nonparaxial single pixel imaging. To overcome this hurdle, we use two integral image quality assessment techniques from computational imaging theory and estimate the quality of the image in a virtual numerical THz imaging scenario. The localized mean square error metric did not cause additional constraints to the quality of the image, whereas the global mean square error has restricted the range of possible imaging setups. Thus, the computational integral image quality assessment techniques back up the main claim of this study that in the single-pixel imaging the resolution is decoupled from the image brightness.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"34 2","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139238831","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-31DOI: 10.3952/physics.2023.63.2.2
D. Abramavičius
Various types of defect clusters are generated in bulk Si-based high-energy particle detectors. They become either recombination centres or charge trapping centres. Populated trapping centres create internal fields which may affect the dynamics and recombination of remaining free charges. In the semiclassical regime, the charge dynamics can be described by the Boltzmann equation. In this paper, the stochastic description is presented as an alternative to a direct solution of the Boltzmann equation approach. It is demonstrated that the hole dynamics can be described in the overdamped regime in both light-hole and heavy-hole cases. Electrons have to be described by including ballistic components. The theory allows an efficient simulation of the electron and hole dynamics in the vicinity of a defect cluster and demonstrates that local trapping centres are the major components enabling fast charge recombinations. The dipolar type internal fields of permanently trapped charges only weakly influence the charge recombination kinetics.
{"title":"Stochastic theory of charge dynamics and recombination in defect clusters in bulk silicon.","authors":"D. Abramavičius","doi":"10.3952/physics.2023.63.2.2","DOIUrl":"https://doi.org/10.3952/physics.2023.63.2.2","url":null,"abstract":"Various types of defect clusters are generated in bulk Si-based high-energy particle detectors. They become either recombination centres or charge trapping centres. Populated trapping centres create internal fields which may affect the dynamics and recombination of remaining free charges. In the semiclassical regime, the charge dynamics can be described by the Boltzmann equation. In this paper, the stochastic description is presented as an alternative to a direct solution of the Boltzmann equation approach. It is demonstrated that the hole dynamics can be described in the overdamped regime in both light-hole and heavy-hole cases. Electrons have to be described by including ballistic components. The theory allows an efficient simulation of the electron and hole dynamics in the vicinity of a defect cluster and demonstrates that local trapping centres are the major components enabling fast charge recombinations. The dipolar type internal fields of permanently trapped charges only weakly influence the charge recombination kinetics.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":"1 1","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41518152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-31DOI: 10.3952/physics.2023.63.2.3
J. Vaitkus, A. Mekys
The upgrading of ionizing radiation detectors is an actual problem especially related to the high energy physics and space research experiments. The simplest way to restore the signal of the irradiation degraded detector is the increase of the detector bias voltage. This method is widely used worldwide, including high energy physics experiments in ATLAS and CMS. This work presents an effect, which was caused by increased bias voltage in detectors irradiated to extreme high neutron fluence at low temperature. The effect could be related to the increase of surface recombination velocity.The intrinsic photoconductivity spectra were exploited in order to investigate the properties of highly irradiated silicon as this effect depends on parameters that are important in radiation detectors. Two characteristic effects were observed in such highly irradiated samples: the increase of photoconductivity quantum yield and the enhancement of surface recombination at higher bias voltages. The increase of the quantum yield was analyzed in Ref. [1]. The increase of the surface recombination with bias electric field was analyzed in this work as an extension of the performed investigation in the same samples as in Ref. [1]. The investigated silicon samples were irradiated by neutrons to wide range fluence up to 1017 n/cm2.The origin of this effect was analyzed and related to the radiation clusters, which decrease the free carrier lifetime.
{"title":"Increase of the surface recombination velocity at high bias voltage in silicon irradiated by neutrons to extremely high fluences","authors":"J. Vaitkus, A. Mekys","doi":"10.3952/physics.2023.63.2.3","DOIUrl":"https://doi.org/10.3952/physics.2023.63.2.3","url":null,"abstract":"The upgrading of ionizing radiation detectors is an actual problem especially related to the high energy physics and space research experiments. The simplest way to restore the signal of the irradiation degraded detector is the increase of the detector bias voltage. This method is widely used worldwide, including high energy physics experiments in ATLAS and CMS. This work presents an effect, which was caused by increased bias voltage in detectors irradiated to extreme high neutron fluence at low temperature. The effect could be related to the increase of surface recombination velocity.The intrinsic photoconductivity spectra were exploited in order to investigate the properties of highly irradiated silicon as this effect depends on parameters that are important in radiation detectors. Two characteristic effects were observed in such highly irradiated samples: the increase of photoconductivity quantum yield and the enhancement of surface recombination at higher bias voltages. The increase of the quantum yield was analyzed in Ref. [1]. The increase of the surface recombination with bias electric field was analyzed in this work as an extension of the performed investigation in the same samples as in Ref. [1]. The investigated silicon samples were irradiated by neutrons to wide range fluence up to 1017 n/cm2.The origin of this effect was analyzed and related to the radiation clusters, which decrease the free carrier lifetime.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44183248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-31DOI: 10.3952/physics.2023.63.2.6
V. Romanenko, G. Lujaniene, S. Šemčuk, J. Mažeika, O. Jefanova
The Curonian Lagoon is a unique system that is a temporary reservoir of water, accumulating about 62% of the suspended solids in the river runoff. The average activity of plutonium in the suspended particulate matter in the water of the Neris River was 0.26±0.02 Bq/kg, and the activity of 137Cs ranged from 23±8 to 49±12 Bq/kg. The average 137Cs flux to the Curonian Lagoon in the particulate and dissolved species was estimated to be (78±61) × 109 Bq/year. Preliminary estimates indicate that the annual input of 239,240Pu from the Neman River into the Curonian Lagoon is about 0.9 GBq, of which 0.56 GBq accumulates in the sediment of the lagoon.
{"title":"Assessment of the input of particulate 239,240Pu and 137Cs from the Neman River into the Curonian Lagoon","authors":"V. Romanenko, G. Lujaniene, S. Šemčuk, J. Mažeika, O. Jefanova","doi":"10.3952/physics.2023.63.2.6","DOIUrl":"https://doi.org/10.3952/physics.2023.63.2.6","url":null,"abstract":"The Curonian Lagoon is a unique system that is a temporary reservoir of water, accumulating about 62% of the suspended solids in the river runoff. The average activity of plutonium in the suspended particulate matter in the water of the Neris River was 0.26±0.02 Bq/kg, and the activity of 137Cs ranged from 23±8 to 49±12 Bq/kg. The average 137Cs flux to the Curonian Lagoon in the particulate and dissolved species was estimated to be (78±61) × 109 Bq/year. Preliminary estimates indicate that the annual input of 239,240Pu from the Neman River into the Curonian Lagoon is about 0.9 GBq, of which 0.56 GBq accumulates in the sediment of the lagoon.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45530600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-05-31DOI: 10.3952/physics.2023.63.2.1
Y. Qian, L. Wang, G. Shi, Y. Zhang, Z. Sun, Y. Lin
The impact of group velocity dispersion (GVD) on femtosecond laser filamentation with the higher-order Kerreffect is studied at different atmospheric pressures. The results show that GVD makes the collapse distance to not meet the semi-empirical formula proposed by Dawes and Marburger, suppresses multiple focusing and splitting in time during the propagation process, and reduces the length of filament. In addition, we also compared the results with those considering only the third-order Kerr effect. This provides some information for the study of whether the defocus effect in the femtosecond laser filamentation is the higher-order Kerr effect or the plasma effect.
{"title":"The impact of groupvelocity dispersion on femtosecond laser filamentation with higher-order Kerr effect at different atmospheric pressures","authors":"Y. Qian, L. Wang, G. Shi, Y. Zhang, Z. Sun, Y. Lin","doi":"10.3952/physics.2023.63.2.1","DOIUrl":"https://doi.org/10.3952/physics.2023.63.2.1","url":null,"abstract":"The impact of group velocity dispersion (GVD) on femtosecond laser filamentation with the higher-order Kerreffect is studied at different atmospheric pressures. The results show that GVD makes the collapse distance to not meet the semi-empirical formula proposed by Dawes and Marburger, suppresses multiple focusing and splitting in time during the propagation process, and reduces the length of filament. In addition, we also compared the results with those considering only the third-order Kerr effect. This provides some information for the study of whether the defocus effect in the femtosecond laser filamentation is the higher-order Kerr effect or the plasma effect.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":" ","pages":""},"PeriodicalIF":0.6,"publicationDate":"2023-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44451166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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