Fast 2-D and 3-D Terahertz Imaging With a Quantum-Cascade Laser and a Scanning Mirror

Rothbart, Nick; Richter, Heiko; Wienold, Martin; Schrottke, L.; Grahn, H. T.; Hübers, Heinz‐Wilhelm

doi:10.1109/tthz.2013.2273226

Cited by 50 publications

(19 citation statements)

References 27 publications

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“…As described in [16], the beam profile is measured with a mid-infrared microbolometer camera (Infratec Variocam), which has been modified for THz applications. Figure 2(a) shows a beam profile at the intersection of the optical axis with the object plane.…”

Section: Optical Properties and Qcl Characterizationmentioning

confidence: 99%

High-spectral-resolution terahertz imaging with a quantum-cascade laser

Hagelschuer¹,

Rothbart²,

Richter³

et al. 2016

Opt. Express

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We report on a high-spectral-resolution terahertz imaging system operating with a multi-mode quantum-cascade laser (QCL), a fast scanning mirror, and a sensitive Ge:Ga detector. By tuning the frequency of the QCL, several spectra can be recorded in 1.5 s during the scan through a gas cell filled with methanol (CH₃OH). These experiments yield information about the local absorption and the linewidth. Measurements with a faster frame rate of up to 3 Hz allow for the dynamic observation of CH₃OH gas leaking from a terahertz-transparent tube into the evacuated cell. In addition to the relative absorption, the local pressure is mapped by exploiting the effect of pressure broadening.

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Section: Optical Properties and Qcl Characterizationmentioning

confidence: 99%

High-spectral-resolution terahertz imaging with a quantum-cascade laser

Hagelschuer¹,

Rothbart²,

Richter³

et al. 2016

Opt. Express

Self Cite

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“…For example, early techniques employing thermal detectors such as Golay cells and bolometers were limited to response times on the order of 100 ms per pixel [8]. While some techniques such as self-mixing in quantum cascade lasers (QCLs) can capture pixel data at significantly higher rates [9], they are limited by the speed at which they can raster between pixels [10]. Systems employing digital mirror devices to create coded apertures can image at spatial resolutions below the diffraction limit [11], but the added processing time means that these techniques are not relevant for a real-time system.…”

Section: Introductionmentioning

confidence: 99%

Full-Field Terahertz Imaging at Kilohertz Frame Rates Using Atomic Vapor

et al. 2020

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There is much interest in employing terahertz (THz) radiation across a range of imaging applications, but so far, technologies have struggled to achieve the necessary frame rates. Here, we demonstrate a THz imaging system based upon efficient THz-to-optical conversion in atomic vapor, where full-field images can be collected at ultrahigh speeds using conventional optical camera technology. For a 0.55-THz field, we show an effective 1-cm 2 sensor with near diffraction-limited spatial resolution and a minimum detectable power of ð190 AE 30Þ fW s −1=2 per ð40 × 40Þ μm 2 pixel capable of video capture at 3000 frames per second. This combination of speed and sensitivity represents a step change in the state of the art of THz imaging and will likely lead to its uptake in wider industrial settings.

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“…15 THz-TDS systems are powerful tools for material spectroscopy, layer inspection, and transmission imaging of packaged objects. 16 These capabilities of THz-TDS systems are utilized in authentication, [17][18][19] nondestructive inspection of composite materials, [20][21][22][23][24][25][26][27][28] threedimensional imaging, [29][30][31][32] metrology and quality control of industrial products, [33][34][35][36][37] detection of concealed weapons, [38][39][40][41][42][43][44][45] art investigations, 46,47 tomography, [48][49][50][51][52] biomedical diagnosis, [53][54][55][56] material characterization, [57][58][59][60][61][62] thickness measurement, …”

Section: Introductionmentioning

confidence: 99%

Review of GaN-based devices for terahertz operation

Ahi

2017

Opt. Eng

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Abstract. GaN provides the highest electron saturation velocity, breakdown voltage, operation temperature, and thus the highest combined frequency-power performance among commonly used semiconductors. The industrial need for compact, economical, high-resolution, and high-power terahertz (THz) imaging and spectroscopy systems are promoting the utilization of GaN for implementing the next generation of THz systems. As it is reviewed, the mentioned characteristics of GaN together with its capabilities of providing high two-dimensional election densities and large longitudinal optical phonon of ∼90 meV make it one of the most promising semiconductor materials for the future of the THz emitters, detectors, mixers, and frequency multiplicators. GaNbased devices have shown capabilities of operation in the upper THz frequency band of 5 to 12 THz with relatively high photon densities in room temperature. As a result, THz imaging and spectroscopy systems with high resolution and deep depth of penetration can be realized through utilizing GaN-based devices. A comprehensive review of the history and the state of the art of GaN-based electronic devices, including plasma heterostructure field-effect transistors, negative differential resistances, hetero-dimensional Schottky diodes, impact avalanche transit times, quantum-cascade lasers, high electron mobility transistors, Gunn diodes, and tera field-effect transistors together with their impact on the future of THz imaging and spectroscopy systems is provided.

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Fast 2-D and 3-D Terahertz Imaging With a Quantum-Cascade Laser and a Scanning Mirror

Cited by 50 publications

References 27 publications

High-spectral-resolution terahertz imaging with a quantum-cascade laser

High-spectral-resolution terahertz imaging with a quantum-cascade laser

Full-Field Terahertz Imaging at Kilohertz Frame Rates Using Atomic Vapor

Review of GaN-based devices for terahertz operation

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