scholarly journals Silicon Lens Optimization to Create Diffuse, Uniform Illumination from Incoherent THz Source Arrays

2021 ◽  
Author(s):  
Robin Zatta ◽  
Daniel Headland ◽  
Eamal Ashna ◽  
Ritesh Jain ◽  
Philipp Hillger ◽  
...  
Keyword(s):  
Integrated Circuit ◽  
Radiation Power ◽  
Thz Radiation ◽  
Far Field ◽  
Uniform Illumination ◽  
Silicon Lens ◽  
Thz Sources ◽  
Source Array ◽  
Illumination Source ◽  
Thz Power

AbstractArrays of terahertz (THz) sources provide a pathway to overcoming the radiation power limitations of single sources. Several independent sources of THz radiation may be implemented in a single integrated circuit, thereby realizing a monolithic THz source array of high output power. Integrated THz sources must generally be backside-coupled to extended hemispherical dielectric lenses in order to suppress substrate modes and extract THz power. However, this lens also increases antenna gain and thereby produces several non-overlapping beams. This is because individual source pixels are relatively large. Hence, their spatial separation on-chip translates to angular separation in the far-field. In other words, there are gaps in their field of view into which very little THz power is projected. Therefore, they cannot homogeneously illuminate an imaging target. This article presents a simple, practical, and scalable method to convert arrays of incoherent THz sources into a diffuse, uniform illumination source without the need for reducing pixel size. Briefly, individual beam divergence is optimized by tailoring the dimensions of the extended hemispherical dielectric lens such that the far-field beams of adjacent source pixels overlap and combine to form a uniform far-field beam. We applied this method to an incoherent 8 × 8-pixel THz source array radiating 10.3 dBm at 0.42 THz as a proof of concept and thereby realized a 10.3-dBm 0.42-THz diffuse, uniform illumination source that was then deployed in a demonstration of THz active imaging.

scholarly journals Visible Measurement of Terahertz Power Based on Capsulized Cholesteric Liquid Crystal Film

2018 ◽  
Vol 8 (12) ◽  
pp. 2580 ◽  
Author(s):  
Lei Wang ◽  
Hongsong Qiu ◽  
Thanh Phan ◽  
Kosaku Kato ◽  
Boyoung Kang ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Color Change ◽  
Radiation Power ◽  
Cholesteric Liquid Crystal ◽  
Cost Effective ◽  
Thz Radiation ◽  
Power Meter ◽  
Crystal Film ◽  
Quantitative Visualization ◽  
Thz Power

We demonstrate a new method to detect terahertz (THz) power using a temperature-supersensitive capsulized cholesteric liquid crystal film based on the thermochromic and thermodiffusion effect, which is clearly observed. A quantitative visualization of the THz intensity up to 4.0 × 103 mW/cm2 is presented. The diameter of the color change area is linearly dependent on the THz radiation power above 0.07 mW in the steady state. Moreover, the THz power can be detected for 1 sec of radiation with a parabolic relation to the color change area. The THz power meter is robust, cost-effective, portable, and even flexible, and can be used in applications such as THz imaging, biological sensing, and inspection.

scholarly journals Silicon Field Effect Transistor as the Nonlinear Detector for Terahertz Autocorellators

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3735 ◽  
Author(s):  
Kęstutis Ikamas ◽  
Ignas Nevinskas ◽  
Arūnas Krotkus ◽  
Alvydas Lisauskas
Keyword(s):  
Threshold Voltage ◽  
Field Effect ◽  
Field Effect Transistor ◽  
Cryogenic Cooling ◽  
Thz Radiation ◽  
Gate Bias ◽  
Large Signal ◽  
Wide Range ◽  
Effect Transistor ◽  
Thz Power

We demonstrate that the rectifying field effect transistor, biased to the subthreshold regime, in a large signal regime exhibits a super-linear response to the incident terahertz (THz) power. This phenomenon can be exploited in a variety of experiments which exploit a nonlinear response, such as nonlinear autocorrelation measurements, for direct assessment of intrinsic response time using a pump-probe configuration or for indirect calibration of the oscillating voltage amplitude, which is delivered to the device. For these purposes, we employ a broadband bow-tie antenna coupled Si CMOS field-effect-transistor-based THz detector (TeraFET) in a nonlinear autocorrelation experiment performed with picoseconds-scale pulsed THz radiation. We have found that, in a wide range of gate bias (above the threshold voltage V th = 445 mV), the detected signal follows linearly to the emitted THz power. For gate bias below the threshold voltage (at 350 mV and below), the detected signal increases in a super-linear manner. A combination of these response regimes allows for performing nonlinear autocorrelation measurements with a single device and avoiding cryogenic cooling.

scholarly journals Design aspects of Bi2Sr2CaCu2O8+δ THz sources: optimization of thermal and radiative properties

2021 ◽  
Author(s):  
Mikhail M Krasnov ◽  
Natalia D Novikova ◽  
Roger Cattaneo ◽  
Alexey A Kalenyuk ◽  
Vladimir M Krasnov
Keyword(s):  
Experimental Data ◽  
Power Efficiency ◽  
Open Space ◽  
Radiation Power ◽  
Impedance Matching ◽  
Dipole Antenna ◽  
Radiative Properties ◽  
Heat Management ◽  
Order Of Magnitude ◽  
Thz Sources

Impedance matching and heat management are important factors influencing performance of THz sources. In this work we analyze thermal and radiative properties of such devices based on mesa structures of a layered high-temperature superconductor Bi2Sr2CaCu2O8+δ. Two types of devices are considered, containing either a conventional large single crystal, or a whisker. We perform numerical simulations for various geometrical configurations and parameters and make a comparison with experimental data for the two types of devices. It is demonstrated that the structure and the geometry of both the superconductor and the electrodes are playing important roles. In crystal-based devices an overlap between the crystal and the electrode leads to appearance of a large parasitic capacitance, which shunts THz emission and prevents impedance matching with open space. The overlap is avoided in whisker-based devices. Furthermore, the whisker and the electrodes form a turnstile (crossed-dipole) antenna facilitating good impedance matching. This leads to more than an order of magnitude enhancement of the radiation power efficiency in whisker-based, compared to crystal-based devices. These results are in good agreement with presented experimental data.

scholarly journals PENCITRAAN PEMETAAN PANAS PENYERAPAN RADIASI TERAHERTZ (THz) DALAM JARINGAN BIOLOGIS MENGGUNAKAN MODEL SIMULINK-MATLAB

2020 ◽  
Vol 6 (2) ◽  
pp. 252
Author(s):  
Dewi Kurnia ◽  
Muhammmad Hamdi ◽  
Juandi M
Keyword(s):  
Muscle Tissue ◽  
Biological Networks ◽  
Biological Tissue ◽  
Imaging Techniques ◽  
High Water ◽  
High Water Content ◽  
Thz Radiation ◽  
Fat Tissue ◽  
Lower Temperature ◽  
Thz Power

ABSTRAKRadiasi THz memiliki sifat yang membuatnya lebih menarik dan efektif dalam bidang teknik pencitraan biomedis. Hal ini dikarenakan radiasi THz tidak mengionisasi dan merusak jaringan. Penelitian ini menggunakan sampel jaringan biologis sapi yaitu  jaringan kulit, lemak, tumor dan otot. Tujuan dari penelitian untuk mengetahui suatu jaringan terindikasi abnormal atau normal dengan melihat pemetaan panas yang dihasilkan dari penyerapan radiasi THz dalam jaringan biologis sapi dengan cara pemodelan. Penelitian ini menggunakan teknik komputasi biofisik dengan medel simulink-matlab. Rentang frekuensi radiasi THz yang digunakan 0,1 - 1 THz, daya 50 – 150 mW serta kerapatan daya 5 - 25 mW/mm3. Rasio dan temperatur dari masing-masing jaringan yaitu lemak 0,25 T/25 oC (T = 6,25 oC ), kulit 0,432 T/25oC (10,8 oC), otot 0,675 T/25oC (16,88 oC) dan Tumor 0,9 T/25oC (22,50 oC). Hasil penelitian menunjukkan bahwa Jaringan lemak memiliki produksi panas yang lebih kecil dan temperatur yang lebih rendah dari jaringan kulit dan otot. Hal ini dikarenakan jaringan lemak memiliki kadar air yang tinggi dengan konsentrasi yang lebih encer sehingga radiasi THz lebih banyak terserap dengan energi yang lebih cepat habis sesuai penetrasi jaringan. Kata kunci:  terahertz; pemetaan panas; jaringan biologis; simulink-matlab.                                                                                                                                       ABSTRACTTerahertz (THz) radiation has properties that make it more attractive and effective in the field of biomedical imaging techniques. This is because THz radiation does not ionize and damage tissue. This study used a sample of bovine biological tissue, namely skin, fat, tumor and muscle tissue. The aim of this research is to find out whether a tissue is indicated as abnormal or normal by looking at the heat mapping generated from the absorption of THz radiation in the biological tissue of cattle by means of modeling. This study uses biophysical computation techniques with the simulink-matlab method. The range of THz radiation frequency used is 0.1 - 1 THz, power 50 - 150 mW and power density 5 - 25 mW / mm3. The ratio and temperature of each tissue were fat 0.25 T / 25 oC (T = 6.25 oC), skin 0.432 T / 25oC (10.8 oC), muscle 0.675 T / 25oC (16.88 oC) and Tumor 0.9 T / 25oC (22.50 oC). The results showed that fat tissue has less heat production and a lower temperature than skin and muscle tissue. This is because the fat tissue has a high water content with a more dilute concentration so that more THz radiation is absorbed with energy that runs out faster according to tissue penetration. Keywords: terahertz; heat mapping; biological networks; simulink-matlab.

Far-Field Performances Prediction of High Frequency Projectors Using Secondary Source Array Method

2016 ◽  
Vol 25 (02) ◽  
pp. 1750002 ◽  
Author(s):  
Shiquan Wang
Keyword(s):  
High Frequency ◽  
Near Field ◽  
Directivity Pattern ◽  
Field Method ◽  
Voltage Response ◽  
Secondary Source ◽  
Far Field ◽  
Comparison Of The Results ◽  
Source Array ◽  
Good Agreement

This paper investigates the prediction of the far-field performances of high frequency projectors using the second source array method (SSAM). The far-field parameters can be calculated accurately using the complex acoustic pressure data of two very close parallel planes which lie in the near-field region of the projector. The paper simulates the feasibility of predicting the far-field parameters such as transmitting voltage response and the far-field directivity pattern. The predicting results are compared with that calculated using boundary element method (BEM). It shows very good agreement between the two methods. A planar high frequency projector is measured using the near-field method. In order to verify the predicting results, the far-field measurement is performed for the same projector. The comparison of the results shows that the near-field method is capable to precisely predict the far-field parameters of the projector.

Wavelet estimation for a multidimensional acoustic or elastic earth

Geophysics ◽  
1990 ◽  
Vol 55 (7) ◽  
pp. 902-913 ◽  
Author(s):  
Arthur B. Weglein ◽  
Bruce G. Secrest
Keyword(s):  
Estimation Method ◽  
Normal Derivative ◽  
Source Spectrum ◽  
Earth Model ◽  
Far Field ◽  
Wavelet Estimation ◽  
Seismic Wavelet ◽  
Array Pattern ◽  
The Earth ◽  
Source Array

A new and general wave theoretical wavelet estimation method is derived. Knowing the seismic wavelet is important both for processing seismic data and for modeling the seismic response. To obtain the wavelet, both statistical (e.g., Wiener‐Levinson) and deterministic (matching surface seismic to well‐log data) methods are generally used. In the marine case, a far‐field signature is often obtained with a deep‐towed hydrophone. The statistical methods do not allow obtaining the phase of the wavelet, whereas the deterministic method obviously requires data from a well. The deep‐towed hydrophone requires that the water be deep enough for the hydrophone to be in the far field and in addition that the reflections from the water bottom and structure do not corrupt the measured wavelet. None of the methods address the source array pattern, which is important for amplitude‐versus‐offset (AVO) studies. This paper presents a method of calculating the total wavelet, including the phase and source‐array pattern. When the source locations are specified, the method predicts the source spectrum. When the source is completely unknown (discrete and/or continuously distributed) the method predicts the wavefield due to this source. The method is in principle exact and yet no information about the properties of the earth is required. In addition, the theory allows either an acoustic wavelet (marine) or an elastic wavelet (land), so the wavelet is consistent with the earth model to be used in processing the data. To accomplish this, the method requires a new data collection procedure. It requires that the field and its normal derivative be measured on a surface. The procedure allows the multidimensional earth properties to be arbitrary and acts like a filter to eliminate the scattered energy from the wavelet calculation. The elastic wavelet estimation theory applied in this method may allow a true land wavelet to be obtained. Along with the derivation of the procedure, we present analytic and synthetic examples.

Design of an integrating sphere as a uniform illumination source

1997 ◽  
Vol 40 (2) ◽  
pp. 131-134 ◽  
Author(s):  
A. Ducharme ◽  
A. Daniels ◽  
E. Grann ◽  
G. Boreman
Keyword(s):  
Integrating Sphere ◽  
Uniform Illumination ◽  
Illumination Source

scholarly journals Broadband THz Sources from Gases to Liquids

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Yiwen E ◽  
Liangliang Zhang ◽  
Anton Tcypkin ◽  
Sergey Kozlov ◽  
Cunlin Zhang ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Laser Pulses ◽  
High Energy ◽  
Wave Generation ◽  
High Energy Density ◽  
Intense Laser ◽  
Thz Radiation ◽  
Flowing Liquid ◽  
Thz Wave ◽  
Thz Sources

Matters are generally classified within four states: solid, liquid, gas, and plasma. Three of the four states of matter (solid, gas, and plasma) have been used for THz wave generation with short laser pulse excitation for decades, including the recent vigorous development of THz photonics in gases (air plasma). However, the demonstration of THz generation from liquids was conspicuously absent. It is well known that water, the most common liquid, is a strong absorber in the far infrared range. Therefore, liquid water has historically been sworn off as a source for THz radiation. Recently, broadband THz wave generation from a flowing liquid target has been experimentally demonstrated through laser-induced microplasma. The liquid target as the THz source presents unique properties. Specifically, liquids have the comparable material density to that of solids, meaning that laser pulses over a certain area will interact with three orders more molecules than an equivalent cross-section of gases. In contrast with solid targets, the fluidity of liquid allows every laser pulse to interact with a fresh area on the target, meaning that material damage or degradation is not an issue with the high-repetition rate intense laser pulses. These make liquids very promising candidates for the investigation of high-energy-density plasma, as well as the possibility of being the next generation of THz sources.

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