Lithuanian Journal of Physics最新文献_第2页

On nonparaxial single-pixel imaging of semitransparent objects using flat diffractive optics 利用平面衍射光学对半透明物体进行非同轴单像素成像

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-12-13 DOI: 10.3952/physics.2023.63.4.3

P. Kizevičius, S. Orlov, K. Mundrys, V. Jukna, L. Minkevičius, G. Valušis

{"title":"On nonparaxial single-pixel imaging of semitransparent objects using flat diffractive optics","authors":"P. Kizevičius, S. Orlov, K. Mundrys, V. Jukna, L. Minkevičius, G. Valušis","doi":"10.3952/physics.2023.63.4.3","DOIUrl":"https://doi.org/10.3952/physics.2023.63.4.3","url":null,"abstract":"\u0000 \u0000 \u0000 \u0000 \u0000 \u0000High numerical apertures can result in distortions appearing in a single-shot image, rendering the acquisition of usable images challenging, if not outright impossible. However, in the realm of single-pixel imaging, various strategies can be employed to effectively inspect objects with an excellent resolution, contrast and brightness. Recent advancements in flat photonic components have facilitated the development of compact nonparaxial imaging systems, which show great promise, particularly in the THz range of wavelengths. These innovations hold the potential to advance fields such as communication, material inspection and spectroscopy. In this study, we delve into the imaging of semi-transparent objects with varying levels of detail. Furthermore, we introduce a nonparaxial design for a flat hyperbolical lens and evaluate its performance in these imaging scenarios, comparing it to structured illumination techniques involving Airy, Bessel, and common thin lens configurations. We present findings regarding potential improvements in imaging attributable to the nonparaxial hyperbolical lens. \u0000 \u0000 \u0000 \u0000 \u0000 \u0000","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139004357","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}

引用次数: 0

Guided mode resonances for angular and spectral filtering 用于角度和频谱滤波的导波模式共振

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-12-13 DOI: 10.3952/physics.2023.63.4.2

I. Lukosiunas, J. Nikitina, D. Gailevičius, L. Grinevičiūtė, K. Staliūnas

{"title":"Guided mode resonances for angular and spectral filtering","authors":"I. Lukosiunas, J. Nikitina, D. Gailevičius, L. Grinevičiūtė, K. Staliūnas","doi":"10.3952/physics.2023.63.4.2","DOIUrl":"https://doi.org/10.3952/physics.2023.63.4.2","url":null,"abstract":"\u0000 \u0000 \u0000The development of devices based on compact waveguides is a rapidly evolving field. A unique variation of such devices is the Fano-like resonance dielectric spectral and spatial filtre, made from a dielectric conformal thin film on a surface relief grating. It can be used in a normal (or oblique) angle-of-incidence configuration. This device facilitates directional selectivity, which is useful for transverse-mode cleaning in short optical cavities. It can also be enhanced by using leaky-mode effects to produce even sharper spectral features. However, a perfect spatial filtre should be as invariant as possible in the spectral and enhanced angular domains. Here, we solved the inverse design problem to produce such an effect. Numerically, we tuned the surface profile of the substrate grating, assuming a conformal layer on top. This resulted in trapezoidal relief patterns followed by narrow flat-top angular features. The combination of leaky mode effect and enhanced device topology will enable efficient and useful devices with a bandwidth of 50 nm and even more in the future. \u0000 \u0000 \u0000","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139005530","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}

引用次数: 0

Two-dimensional hydrodynamic modelling of AlGaN/GaN transistor-based THz detectors 基于氮化铝/氮化镓晶体管的太赫兹探测器的二维流体力学建模

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-12-13 DOI: 10.3952/physics.2023.63.4.4

J. Vyšniauskas, K. Ikamas, D. Vizbaras, A. Lisauskas

引用次数: 0

Terahertz bow-tie diode based on asymmetrically shaped AlGaN/GaN heterostructures 基于非对称形状氮化铝/氮化镓异质结构的太赫兹弓形二极管

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-12-13 DOI: 10.3952/physics.2023.63.4.1

J. Jorudas, D. Seliuta, L. Minkevičius, V. Janonis, L. Subačius, D. Pashnev, S. Pralgauskaitė, J. Matukas, K. Ikamas, A. Lisauskas, E. Šermukšnis, J. Liberis, V. Kovalevskij, I. Kašalynas

{"title":"Terahertz bow-tie diode based on asymmetrically shaped AlGaN/GaN heterostructures","authors":"J. Jorudas, D. Seliuta, L. Minkevičius, V. Janonis, L. Subačius, D. Pashnev, S. Pralgauskaitė, J. Matukas, K. Ikamas, A. Lisauskas, E. Šermukšnis, J. Liberis, V. Kovalevskij, I. Kašalynas","doi":"10.3952/physics.2023.63.4.1","DOIUrl":"https://doi.org/10.3952/physics.2023.63.4.1","url":null,"abstract":"\u0000 \u0000 \u0000Asymmetrical shaping of AlGaN/GaN heterostructures containing a conductive layer of two-dimensional electron gas (2DEG) was used for the development of bow-tie (BT) diodes for room temperature terahertz (THz) detection. Considering operation of the THz BT diode in the unbiased mode as preferable for practical applications, we investigated the diodes with an obvious asymmetry of IV characteristics, which was found to be more pronounced with the decrease of an apex width, resulting in the sensitive THz detection. A nonuniform heating of carriers in a metalized leaf of the BT diode was attributed as the main mechanism that caused the rectification of THz waves. The responsivity and noise-equivalent power (NEP) at the fundamental antenna frequency of 150 GHz were up to 4 V/W and 2 nW/√Hz, respectively. Such high sensitivity of BT diodes allowed us to measure for the first time the response spectrum of the asymmetric BT antenna demonstrating fundamental and higher order resonances in good agreement with finite-difference time-domain simulation data in a broad spectrum range. The detailed investigation of the lowand high-frequency noise characteristics of AlGaN/GaN BT diodes revealed that only thermal noise needs to be considered for the unbiased operation, the value of which was relatively low due to a high density of 2DEG enabling low resistivity values. Moreover, we observed that the responsivity of BT diode scales with its resistance, revealing that tapering of the diode apex below a few microns could be ineffective in applications which require low NEP values. \u0000 \u0000 \u0000","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139004893","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}

引用次数: 0

Pyro lyzed photoresist thin film: effect of electron beam patterning on DC and THz conductivity 热解光刻胶薄膜：电子束图案化对直流和太赫兹电导率的影响

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-11-26 DOI: 10.3952/physics.2023.63.3.6

J. Jorudas, H. Rehman, G. Fedorov, M. Cojocari, P. Karvinen, A. Urbanowicz, I. Kašalynas, L. Y. Matzui, Y. Svirko, P. Kuzhira

{"title":"Pyro lyzed photoresist thin film: effect of electron beam patterning on DC and THz conductivity","authors":"J. Jorudas, H. Rehman, G. Fedorov, M. Cojocari, P. Karvinen, A. Urbanowicz, I. Kašalynas, L. Y. Matzui, Y. Svirko, P. Kuzhira","doi":"10.3952/physics.2023.63.3.6","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.6","url":null,"abstract":"Pyrolyzed photoresist films (PPFs), which are formed via vacuum annealing of a photoresist without a catalyst, can be employed for fabrication of graphitic nanostructures by using conventional lithographic techniques. Such approach allows for reduction of technological steps required for fabrication of conductive micro- and nanoelectrodes for different applications. However, the operation frequency range of PPF electrodes is still unknown. Here, we report the results of the comparative study of PPF structures fabricated by electron beam lithography prior and after the annealing process with preference to the first approach. By performing the comparative measurements of PPF transport properties we found that both pre-and post-processed PPFs possess the same conductivities at dc-current and in the frequency range from 0.2 to 1.5 THz. Moreover, we achieved the sheet resistance of 150 nm thick PPFs as low as 570 Ω/sq, which is comparable to that of commercially available chemical vapour deposited (CVD) graphene. These findings open a path for a simple, reproducible and scalable fabrication of graphitic nanocircuits, nanoresonators and passive components suitable for applications in frequencies up to few terahertz.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139235106","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}

引用次数: 0

Sum-frequency generation and amplification processes in semiconductor superlattices 半导体超晶格中的和频产生和放大过程

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-11-26 DOI: 10.3952/physics.2023.63.3.5

V. Čižas, N. Alexeeva, K. Alekseev, G. Valušis

{"title":"Sum-frequency generation and amplification processes in semiconductor superlattices","authors":"V. Čižas, N. Alexeeva, K. Alekseev, G. Valušis","doi":"10.3952/physics.2023.63.3.5","DOIUrl":"https://doi.org/10.3952/physics.2023.63.3.5","url":null,"abstract":"Semiconductor superlattices are very well-known structures due to their specific electron transport properties, making them extremely attractive to be employed in electronic or optoelectronic devices. The interest in such structures has been recently additionally stirred up due to the first successful experimental demonstration of parametric gain in GaAs/AlGaAs superlattices, resulting in the generation of harmonics, half-harmonics and fractional harmonics. This invention paves the way for a successful realization of superlattice-based generators and amplifiers up to the terahertz frequency range. Despite the emerging experimental results and decade-long theoretical research, unresolved aspects, related to the physical processes inside the superlattices, persist. Lately, the biasing effect was extensively analysed for the case of degenerate processes in the superlattice; however, the non-degenerate case was left out of frame until now. Within this research, we further expand the boundaries of previous investigation by exploring the differences of non-degenerate processes. The study uncovers the asymmetry appearance of the probe field vs. relative phase dependences as well as the possibility of parametric fractional frequency generation. Finally, the concept of energy reflow between two participating probes is predicted and discussed.","PeriodicalId":18144,"journal":{"name":"Lithuanian Journal of Physics","volume":null,"pages":null},"PeriodicalIF":0.6,"publicationDate":"2023-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139235679","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}

引用次数: 0

Terahercų emisijos spektroskopija pavidalų panašumui tirti: Ukrainos ir Lietuvos simbolių nagrinėjimas 太赫兹发射光谱分析形状的相似性：乌克兰和立陶宛符号研究

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-11-26 DOI: 10.3952/physics.2023.63.3.7

B. Škėlaitė, V. Jakštas, M. Treideris, A. Bičiūnas, K. Ikamas, R. Butkutė, I. Grigelionis

引用次数: 0

Investigation of blur kernel of terahertz images 太赫兹图像模糊内核研究

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-11-26 DOI: 10.3952/physics.2023.63.3.8

V. Abramova, S. Abramov, V. Lukin, I. Grigelionis, L. Minkevičius, G. Valušis

{"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":null,"pages":null},"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}

引用次数: 0

3D printed diffractive lenses operating at 1 THz 工作频率为 1 太赫兹的 3D 打印衍射透镜

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-11-26 DOI: 10.3952/physics.2023.63.3.2

P. Komorowski, M. Kaluza, S. Surma, A. Siemion

引用次数: 0

Voltage controlled Fabry–Perot modulator 电压控制法布里-珀罗调制器

IF 0.6 4区物理与天体物理

Lithuanian Journal of Physics Pub Date : 2023-11-26 DOI: 10.3952/physics.2023.63.3.3

A. Kamarauskas, L. Staišiūnas, D. Seliuta, G. Šlekas, Ž. Kancleris

引用次数: 0