Terahertz imaging with bow-tie InGaAs-based diode with broken symmetry

Kašalynas, Irmantas; Seliuta, D.; Simniškis, R.; Tamošiūnas, V.; Köhler, K.; Valušis, Gintaras

doi:10.1049/el.2009.0336

Cited by 36 publications

(18 citation statements)

References 6 publications

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“…Therefore, the InGaAs-based diodes due to their sensitivity can be applied for imaging aims. First images taken using InGaAs bow-tie diodes in the subTHz range, at 0.693THz, were demonstrated showing the features of a plastic capsule half-filled with pharmaceutical powder [13]. Here we focused our attention on compact spectroscopic imaging as the device demonstrates operation over a broadband frequency band, up to 2.5THz.…”

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

confidence: 99%

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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: 99%

“…It was measured that the response time of the BT diode is less than few nanoseconds [13]. Moreover, it was demonstrated that an InGaAs-based bow-tie diode is well suited for fast spectroscopic THz imaging.…”

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

confidence: 99%

Bow-tie diodes for terahertz imaging: Comparative study

Valušis¹,

Venckevičius²,

Kašalynas³

2012

Photon. Lett. Poland

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“…The CWTI system relays on an optically pumped molecular THz laser, delivering a discrete spectrum of emission in the range of several mW, as in the work of Kasalynas et al 21 . The laser power was monitored continuously with a bow-tie diode 22 . …”

Section: Experimental Set-upmentioning

confidence: 99%

Detection of colon cancer by terahertz techniques

Wahaia¹,

Valušis

Bernardo³

et al. 2011

SPIE Proceedings

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Normal and cancer affected samples of colon tissue have been measured using transmission time-domain terahertz spectroscopy and continuous wave terahertz imaging. We show that it is possible to distinguish between normal and cancerous regions in the samples when they are fixed in formalin or embedded in paraffin. Plots of the refractive index of normal and cancer affected tissues as well as 2-D transmission THz images are shown. Experimental results will be presented and the conditions for discrimination between normal and affected tissue will be discussed.

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“…Very recently, room temperature THz images below 1 THz have been recorded using InGaAs bow-tie diodes [8]. The device operation principle is based on non-uniform electron heating in bow-tie diode with a spatially broken symmetry -one of its leaves is metallic while another one is semiconductor containing two-dimensional electron gas [9,10].…”

Section: Introductionmentioning

confidence: 99%

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

Minkevičius¹,

Kašalynas²,

Seliuta³

et al. 2010

Lithuanian J. Phys.

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Finite-difference time-domain simulation results in bow-tie InGaAs diodes are presented. Dependences of electric field amplitude on frequency were investigated for various device shapes and sizes. It was shown that two metallized parts of the bow-tie type detector act as the separate antennas causing thus the experimentally observed fast sensitivity reduction at 1.63, 1.83, and 2.51 THz frequencies. Moreover, it has been demonstrated that the estimated effective average refractive index of the region around the antenna for all investigated angles and dimensions is nearly constant, and this constant value could be used for further estimation of frequency dependent properties in the case of other slightly altered bow-tie detector geometry.

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Terahertz imaging with bow-tie InGaAs-based diode with broken symmetry

Cited by 36 publications

References 6 publications

Bow-tie diodes for terahertz imaging: Comparative study

Bow-tie diodes for terahertz imaging: Comparative study

Detection of colon cancer by terahertz techniques

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

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