Continuous and Pulsed THz generation with molecular gas lasers and photoconductive antennas gated by femtosecond pulses

Cruz, Flávio C.; Nogueira, Giovana T.; Costa, Leverson F. L.; Frateschi, Newton C.; Viscovini, Ronaldo Celso; Pereira, D.

doi:10.1109/imoc.2007.4404301

Cited by 4 publications

(3 citation statements)

References 3 publications

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“…Semiconductor Diodes [12][13][14][15][16] Limited Average Difference Freq. Generation [17,18] Limited High Optical Rectification [19,20] Good Good Optical Parametric Oscillators [21,22] Good High Frequency Multiplayers [23] Limited Average Photoconductive Antennas [24,25] Good Low Photomixing [26,27] Good Low Optically Pumped FIR Lasers [28] Limited Good Quantum Cascade Lasers [29,30] Limited Average Backward Wave Oscillators [31,32] Limited Good…”

Section: Source Type Spectral Range Output Powermentioning

confidence: 99%

Remote Spectral Identification in the THz Band with Reflection Spectroscopy in an Open Atmosphere

2023

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Spectroscopy in the terahertz (THz) band has been discussed as a promising tool for identifying substances such as mold in food, narcotics, or explosive materials. Other than the technological limitations, the most important difficulty is the presence of water vapor in the atmosphere, which affects THz measurements. In this paper, we present a systematic approach to the challenging subject of remote identification. We start with a brief analysis of the technical capabilities of the THz components and report the choice of devices for designing an experimental setup for reflection spectroscopy. We follow with the presentation of the transmission THz spectrometer working in an open atmosphere. Research conducted on the transmission configuration provides findings that are implemented in the experimental setup working in a reflective configuration. The final phase is an experiment providing data measured in the reflection configuration with the presence of water vapor, allowing the use of spectra in the identification of the measured samples.

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Section: Source Type Spectral Range Output Powermentioning

confidence: 99%

Remote Spectral Identification in the THz Band with Reflection Spectroscopy in an Open Atmosphere

2023

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“…It was on inversion-rotational transitions of NH 3 molecule that laser radiation was generated by French colleagues on our project during optical pumping of ammonia by a quantum-cascade laser [8]. Typically, a CO 2 laser is used as the pumping source of terahertz gas lasers [7,[9][10] as the most convenient and wellstudied source of radiation. In contrast to a CO 2 laser, a molecular CO laser is capable of operating in the mid-IR range almost simultaneously on hundreds of spectral lines in the wavelength range from 2.5 to 8.7 µm, which makes it possible to significantly increase the number of excited molecules and, accordingly, to enrich spectrum of radiation in the terahertz range.…”

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confidence: 99%

THz sources based on frequency conversion of multi-line molecular lasers in nonlinear crystals and on optically pumped molecular lasers

et al. 2018

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“…For the generation of THz radiation in the aforementioned lower THz frequency range, various THz sources can be used, such as electronic [13] or optoelectronic [14] emitters, semiconductor [15] or molecular gas lasers [16], for high-power generation also gyrotrons [17] and free-electron lasers (FELs) [18]. The useful detectors for specific applications depending on the power level and frequency of the generated signal.…”

Section: Future Applicationsmentioning

confidence: 99%

Room-temperature passive terahertz imaging based on high sensitivity field-effect transistor detectors

Čibiraitė-Lukenskienė¹

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Terahertz (THz) technology is an emerging field that considers the radiation between microwave and far-infrared regions where the electronic and photonic technologies merge. THz generation and THz sensing technologies should fill the gap between photonics and electronics which is defined as a region where THz generation power and THz sensing capabilities are at a low technology readiness level (TRL). As one of the options for THz detection technology, field-effect transistors with integrated antennae were suggested to be used as THz detectors in the 1990s by M. Dyakonov and M. Shur from where the development of field-effect transistor-based detector began. In this work, various FET technologies are presented, such as CMOS, AlGaN/GaN, and graphene-based material systems and their further sensitivity enhancement in order to reach the performance of well-developed Schottky diode-based THz sensing technology. Here presented FET-based detectors were explored in a wide frequency range from 0.1 THz up to 5 THz in narrowband and broadband configurations. For proper implementation of THz detectors, the well-defined characterization is of high importance. Therefore, this work overviews the characterization methods, establishes various definitions of detector parameters, and summarizes the state-of-the-art THz detectors. The electrical, optical, and cryogenic characterization techniques are also presented here, as well as the best results obtained by the development of the characterization methods, namely graphene FET stabilization, low-power THz source characterization for detector calibration, and technology development for cryogenic detection. Following the discussion about the detector characterization, a wide range of THz applications, which were tested during the last four years of Ph.D. and conducted under the ITN CELTA project from HORIZON2020 program, are presented in this work. The studies began with spectroscopy applications and imaging and later developed towards hyperspectral imaging and even passive imaging of human body THz radiation. As various options for THz applications, single-pixel detectors as well as multi-pixel arrays are also covered in this work. The conducted research shows that FET-based detectors can be used for spectroscopy applications or be easily adapted for the relevant frequency range. State-of-the-art detectors considered in this work reach the resonant performance below 20 pW/√Hz at 0.3 THz and 0.5 THz, as well as 404 pW/√Hz cross-sectional NEP at 4.75 THz. The broadband detectors show NEP as low as 25 pW/√Hz at around 0.6 THz for the best AlGaN/GaN design and 25 pW/√Hz around 1 THz for the best CMOS design. As one of the most promising applications, metamaterial characterization was tested using the most sensitive devices. Furthermore, one of the single-pixel devices and a multi-pixel array were tested as an engineering solution for a radio astronomy system called GREAT in a stratosphere observatory named SOFIA. The exploration of the autocorrelation technique using FET-based devices shows the opportunity to employ such detectors for direct detection of THz pulses without an interferometric measurement setup. This work also considers imaging applications, which include near-field and far-field visualization solutions. A considerable milestone for the theory of FET technology was achieved when scanning near-field microscopy led to the visualization of plasma (or carrier density) waves in a graphene FET channel. Whereas another important milestone for the THz technology was achieved when a 3D scan of a mobile phone was performed under the far-field imaging mode. Even though the imaging was done through the phone’s plastic cover, the image displayed high accuracy and good feature recognition of the smartphone, inching the FET-based detector technology ever so close to practical security applications. In parallel, the multi-pixel array testing was carried out on 6x7 pixel arrays that have been implemented in configurable-size aperture and imaging configurations. The configurable aperture size allowed the easier detector focusing procedure and a better fit for the beam size of the incident radiation. The imaging has been tested on various THz sources and compared to the TeraSense 16x16 pixel array. The experimental results show the big advantage of the developed multi-pixel array against the used commercial technology. Furthermore, two ultra-low-power applications have been successfully tested. The application on hyper-frequency THz imaging tested in the specially developed dual frequency comb and our detector system for 300 GHz radiation with 9 spectral lines led to outstanding imaging results on various materials. The passive imaging of human body radiation was conducted using the most sensitive broadband CMOS detector with a log-spiral antenna working in the 0.1 – 1.5 THz range and reaching the optical NEP of 42 pW/√Hz. The NETD of this device reaches 2.1 K and overcomes the performance limit of passive room-temperature imaging of the human body radiation, which was less than 10 K above the room temperature. This experiment opened a completely new field that was explored before only by the multiplier chain-based or thermal detectors. ...

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Continuous and Pulsed THz generation with molecular gas lasers and photoconductive antennas gated by femtosecond pulses

Cited by 4 publications

References 3 publications

Remote Spectral Identification in the THz Band with Reflection Spectroscopy in an Open Atmosphere

Remote Spectral Identification in the THz Band with Reflection Spectroscopy in an Open Atmosphere

THz sources based on frequency conversion of multi-line molecular lasers in nonlinear crystals and on optically pumped molecular lasers

Room-temperature passive terahertz imaging based on high sensitivity field-effect transistor detectors

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