Frequency-dependent properties of InGaAs bow-tie detectors in terahertz range

Minkevičius, Linas; Kašalynas, Irmantas; Seliuta, D.; Tamošiūnas, V.; Valušis, Gintaras

doi:10.3952/lithjphys.50204

Cited by 6 publications

(2 citation statements)

References 11 publications

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“…With a further increase of frequency the sensitivity drops down faster than phenomenological estimates predicted due to weaker coupling of radiation as was evidenced via finitedifference time domain calculations [9]. Experimentally observed peculiarity in a planar n-n + -GaAs structure -an increase of sensitivity at 1.63THz and 2.52THz instead of a general decreasing trend -can be explained by antenna resonances which can be pronounced in such an antennalike structure [12]. Therefore, the InGaAs-based diodes due to their sensitivity can be applied for imaging aims.…”

Section: Bow-tie Diodes For Terahertz Imaging: a Comparative Studymentioning

confidence: 65%

Bow-tie diodes for terahertz imaging: Comparative study

Valušis¹,

Venckevičius²,

Kašalynas³

2012

Photon. Lett. Poland

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Abstract-The concept of broadband bow-tie diodes as terahertz sensors and their possible application for imaging is presented. Different bow-tie sensors fabricated of planar GaAs, modulation doped GaAs/AlGaAs structures and InGaAs layers are compared and discussed. It is demonstrated experimentally that the sensitivity of all studied devices at room temperature is nearly independent of frequency below 1THz and amounts to 0.3V/W for GaAs-based structures and 10V/W for InGaAs sensors. Room temperature terahertz images are recorded at 0.71THz and 1.4THz. Their parameters are considered in comparison with images taken by using commercially available pyroelectric sensors.The implementation of terahertz (THz) radiation in security applications and materials inspection requires reliable and compact solutions in the development of room temperature imaging systems. In these kinds of requirements, preference goes to solid-state-based solutions. A recent major breakthrough made in all-solidstate tunable sources has opened a promising route in the progress of room temperature THz emitters [1]. As concerns room temperature solid-state THz detectors, one can mention Schottky diodes [2], nanometric field effect transistors [3,4] and microbolometers [5,6]. Very recent achievements in compact room temperature spectroscopic [7] and heterodyne THz imaging [8] allowed one to extend the family of compact THz sensors by adding a member of so-called InGaAs based bow-tie (BT) diodes. The sensors exhibit broadband operation as well as relatively simple device production and good reliability.In this paper, we present a comparative study of different BT diode sensors. An operational principle and spectral features of the device is discussed, BT diode's parameters based on InGaAs layers, modulation doped GaAs/AlGaAs structures and planar GaAs are compared.Terahertz images recorded at room temperature using InGaAs BTs are compared with images taken by using commercially available pyro-electric sensors; feasibility for real-time THz imaging is considered, too.The bow-tie diode uses an idea to combine the performance of a bow-tie antenna as a coupler of incident * E-mail: irmantak@ktl.mii.lt, † E-mail: valusis@pfi.lt radiation and the semiconducting part as radiation sensing media. The diode displays structurally broken symmetry as depicted in Fig. 1: One of the two semiconductor leaves is metalized in order to couple incident radiation into the second one, where high mobility electrons are heated nonuniformly by incident THz radiation [9]. As a result, the voltage signal across the leaves is induced without any application of a bias voltage.Three different types of bow-tie diodes having the same geometry, but fabricated of different materials, were studied. The first one was GaAs/AlGaAs modulation doped structures consisting of a 20-nm-thick GaAs cap layer, Si-doped (1×10

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Section: Bow-tie Diodes For Terahertz Imaging: a Comparative Studymentioning

confidence: 65%

Bow-tie diodes for terahertz imaging: Comparative study

Valušis¹,

Venckevičius²,

Kašalynas³

2012

Photon. Lett. Poland

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“…The influence of ground shape on the antenna impedance would no longer be considered if the differential CPSs were adopted. The bowtie structure was first proposed by George et al [19] and applied to many THz detectors [20][21][22][23][24]. Because of the simple structure and low cost, it is a good choice to match the impedance with YBCO JJ mixer and feed it by CPSs.…”

Section: Introductionmentioning

confidence: 99%

High-Tc Superconducting Josephson Junction Harmonic Mixers with Stub Tuners on Integrated Bowtie Antennas

Chun

Gao

et al. 2022

Applied Sciences

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Ordinary mixers can hardly meet the requirements in terahertz (THz) communications due to the low-power and expensive THz sources. Sensitive harmonic mixers have been widely studied to avoid this problem, owing to the fact that the higher the number of harmonics, the lower the local oscillator (LO) frequency, and the lower the cost. High-Tc superconducting (HTS) Josephson junction (JJ) mixers are performing candidates for THz receiver frontends because of the advantages of excellent sensitivity, wide bandwidth, high harmonic number and low LO power requirement. However, the normal-state resistance of HTS JJ is so low that traditional antennas are difficult to match it. In other words, it is quite a challenge to match the input impedance to a low input impedance for traditional antennas, especially for antennas fed by coplanar striplines (CPSs). In this work, based on the structure of bowtie, two types of stub tuners were integrated to decrease the impedance of the bowtie antenna so as to improve the coupling efficiency between the traditional bowtie antenna and the JJ. Furthermore, HTS YBa2Cu3O7-δ (YBCO) JJ harmonic mixers coupled with the proposed structures and fed by CPSs are fabricated and measured. The measurements show that the JJ mixer coupled with a pair of open-end stubs of the bowtie antenna achieves up to 88 harmonics, with a conversion efficiency of −69.6 dB. In contrast, the JJ mixer coupled with a pair of lumped-element stubs of the bowtie antenna only attains to 30 harmonics, with a conversion efficiency of −73.4 dB. Additional numerical simulations indicate that the coupling efficiency is enhanced when the complex impedance of the antenna is explicitly considered. Compared with other coupled traditional antennas, the JJ mixer with bowtie antenna has the largest harmonic number. This work paves the way for the future application of low-frequency and low-cost LO for THz communications.

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Terahertz heterodyne imaging with InGaAs-based bow-tie diodes

Minkevičius¹,

Tamošiūnas²,

Kašalynas³

et al. 2011

Applied Physics Letters

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Room-temperature detection and imaging in transmission and reflection geometries at 0.591 THz with planar asymmetrically shaped InGaAs diodes (also called bow-tie diodes) are demonstrated in direct and heterodyne mode. The sensitivity of the diodes is found to be 6 V/W in direct mode, and the noise-equivalent power (NEP) in direct and heterodyne mode is estimated to be about 4nW / (Wurzel aus Hz) and 230 fW/Hz for a local-oscillator power of 11 µW, respectively. The improvement of the dynamic range by heterodyning over direct power detection amounts to about 20 dB using pixel read-out times relevant to real-time imaging conditions

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Frequency-dependent properties of InGaAs bow-tie detectors in terahertz range

Cited by 6 publications

References 11 publications

Bow-tie diodes for terahertz imaging: Comparative study

Bow-tie diodes for terahertz imaging: Comparative study

High-Tc Superconducting Josephson Junction Harmonic Mixers with Stub Tuners on Integrated Bowtie Antennas

Terahertz heterodyne imaging with InGaAs-based bow-tie diodes

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