Terahertz quartz enhanced photo-acoustic sensor

Borri, Simone; Patimisco, Pietro; Sampaolo, Angelo; Beere, Harvey E.; Ritchie, D. A.; Vitiello, Miriam S.; Scamarcio, Gaetano; Spagnolo, Vincenzo

doi:10.1063/1.4812438

Cited by 114 publications

(80 citation statements)

References 26 publications

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“…4 Due to its non-ionizing nature, 1 THz radiation can penetrate many commonly used dielectrics, 1 otherwise opaque for visible and mid-infrared light, allowing detection of specific spectroscopic features 5 with a sub-millimeter diffractionlimited resolution. µV/W and operating in photovoltage mode at much higher frequencies (2.5 THz).…”

Section: Introductionmentioning

confidence: 99%

High performance bilayer-graphene terahertz detectors

Spirito

Coquillat

Bonis

et al. 2014

Applied Physics Letters

170

132

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We report bilayer-graphene field effect transistors operating as THz broadband photodetectors based on plasma-waves excitation. By employing wide-gate geometries or buried gate configurations, we achieve a responsivity~1.2V/W (1.3 mA/W) and a noise equivalent power~2×10 -9 W/√Hz in the 0.29-0.38THz range, in photovoltage and photocurrent mode. The potential of this technology for scalability to higher frequencies and the development of flexible devices makes our approach competitive for a future generation of THz detection systems.Generation and detection of radiation across the far infrared or Terahertz (THz) region of the electromagnetic spectrum is promising for a large variety of strategic applications, 1 ranging from biomedical diagnostics 2 to process and quality control, 3 homeland security 1 and environmental monitoring. 4 Due to its non-ionizing nature, 1 THz radiation can penetrate many commonly used dielectrics, 1 otherwise opaque for visible and mid-infrared light, allowing detection of specific spectroscopic features 5 with a sub-millimeter diffractionlimited resolution. µV/W and operating in photovoltage mode at much higher frequencies (2.5 THz).Here we report THz detectors operating at RT in either photovoltage or photocurrent mode with a significant enhancement of sensitivity and lowered NEPs compared to the state of the art. This is achieved by using either large (1 µm) gate lengths, or buried gate geometries on a bilayer graphene (BLG) FET. We use BLG instead of single layer graphene (SLG) since the modulation of carrier density was proved to be more effective in the former case, 19 allowing a higher responsivity at THz frequencies.The devices are prepared as follows. Flakes are mechanically exfoliated from graphite 24 on an intrinsic Si substrate covered with 300nm SiO 2 . BLGs are selected and identified by a combination of optical microscopy 25 and Raman spectroscopy. 26,27 These are then used to fabricate two sets of FETs (samples A, B). In A, source (S) and drain (D) contacts are patterned by electron beam lithography (EBL) and metal evaporation (5nm Cr /80 nm Au). The S contact is connected to one lobe of a 50° bow-tie antenna, and D to a 3 metal pad. After placement of 35nm HfO 2 by atomic layer deposition (ALD), the other lobe of the antenna is fabricated, and constitutes the FET gate (g). The channel length is L SD = 2.5 m, while the gate length w G =1 m (Fig. 1a). In B, one lobe of a log-periodic circular-toothed antenna is fabricated by EBL and metal evaporation to act as buried gate. After deposition of 35 nm HfO 2 by ALD, S and D electrodes are fabricated.Similar to sample A, S is the second lobe of the antenna, while the drain is a metal line connecting to a bonding pad. The channel length is 2.5 m, its width 7.5 m, while w G = 0.3m (Fig. 1b). A BLG flake is then placed onto the pre-fabricated electrodes by wet transfer. 28 Fig. 2 compares the Raman spectra of the flake prior and after placement onto the electrodes. The "2D" peak shows the characteristic multi-band s...

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Section: Introductionmentioning

confidence: 99%

High performance bilayer-graphene terahertz detectors

Spirito

Coquillat

Bonis

et al. 2014

Applied Physics Letters

170

132

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“…The ability to operate terahertz frequency quantum cascade lasers 1 (THz QCLs) in continuous-wave (CW) is essential for many applications, including their use in local oscillator systems, 2 spectroscopy/trace-gas detection, [3][4][5][6] and direct bolometric imaging. 7 It is also often important to ensure that the lasers have low dissipated power.…”

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confidence: 99%

Surface-emitting terahertz quantum cascade lasers with continuous-wave power in the tens of milliwatt range

Isac

et al. 2014

Appl. Phys. Lett.

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We demonstrate efficient surface-emitting terahertz frequency quantum cascade lasers with continuous wave output powers of 20-25 mW at 15 K and maximum operating temperatures of 80-85 K. The devices employ a resonant-phonon depopulation active region design with injector, and surface emission is realized using resonators based on graded photonic heterostructures (GPHs). GPHs can be regarded as energy wells for photons and have recently been implemented through grading the period of the photonic structure. In this paper, we show that it is possible to keep the period constant and grade instead the lateral metal coverage across the GPH. This strategy ensures spectrally singlemode operation across the whole laser dynamic range and represents an additional degree of freedom in the design of confining potentials for photons. V C 2014 AIP Publishing LLC.

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“…The width of the QTF prongs was reduced from 2.5 mm to 1 mm with respect to the QTFs employed in [11,12] in order to make them more flexible. Furthermore, the prongs spacing was reduced from 800 µm to 700 µm in order to increase the acoustic wave deflection effects.…”

Section: Methodsmentioning

confidence: 99%

“…Since the sensitivity of QEPAS technique is ultimately limited by the available optical power, QCLs represent the most promising THz light sources for QEPAS applications. Recently, by exploiting suitably designed custom QTFs and THz QCLs we have reported the first demonstration of QEPAS sensor operating in the THz range [11,12].…”

Section: Introductionmentioning

confidence: 99%

THz Quartz-enhanced photoacoustic sensor for H_2S trace gas detection

Spagnolo¹,

Patimisco²,

Pennetta³

et al. 2015

Opt. Express

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Abstract:We report on a quartz-enhanced photoacoustic (QEPAS) gas sensing system for hydrogen sulphide (H 2 S) detection. The system architecture is based on a custom quartz tuning fork (QTF) optoacoustic transducer with a novel geometry and a quantum cascade laser (QCL) emitting 1.1 mW at a frequency of 2.913 THz. The QTF operated on the first flexion resonance frequency of 2871 Hz, with a quality factor Q = 17,900 at 20 Torr. The tuning range of the available QCL allowed the excitation of a H 2 S rotational absorption line with a line-strength as small as S = 1.13·10−22 cm/mol. The measured detection sensitivity is 30 ppm in 3 seconds and 13 ppm for a 30 seconds integration time, which corresponds to a minimum detectable absorption coefficient α min = 2.3·10 −7 cm −1 and a normalized noise-equivalent absorption NNEA = 4.4·10 −10 W·cm −1 ·Hz -1/2 , several times lower than the values previously reported for near-IR and mid-IR H 2 S QEPAS sensors.

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Terahertz quartz enhanced photo-acoustic sensor

Cited by 114 publications

References 26 publications

High performance bilayer-graphene terahertz detectors

High performance bilayer-graphene terahertz detectors

Surface-emitting terahertz quantum cascade lasers with continuous-wave power in the tens of milliwatt range

THz Quartz-enhanced photoacoustic sensor for H_2S trace gas detection

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