Terahertz wavefronts measured using the Hartmann sensor principle

Cui, Meng; Hovenier, J. N.; Ren, Yuan; Polo, Alessandro; Gao, J. R.

doi:10.1364/oe.20.014380

Cited by 12 publications

(16 citation statements)

References 26 publications

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“…The comparative R(z) z 2013 Asia-Pacific Microwave Conference Proceedings results also are presented for a 110GHz Horn at the distance 5cm from the aperture (Fig.4-c). a) 60GHz ; on aperture b) 60GHz ; 5cm distance c) 110GHz ; 5cm distance Formulas (3)(4) provide simple relation between the source geometry/characteristics and the beam phase at every point. This closed-form relation can be used for a parametric erroranalysis and uncertainty estimation, as well.…”

Section: Resultsmentioning

confidence: 99%

“…Thus, the evaluation of the phasedistribution on a planar surface (perpendicular to the wave propagation direction) is a prerequisite for measurement accuracy. Both theoretical method and measurement can be used for this issue [3]. In this paper, an analytical method is used to find the phase distribution based on the wave-front curvature of a quasiGaussian beam (Fig.…”

Section: Introductionmentioning

confidence: 99%

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Analytical study of mm-wave and THz beams, application to RF metrology

Kazemipour

Kleine‐Ostmann

Schräder

2013

2013 Asia-Pacific Microwave Conference Proceedings (APMC)

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Using mm-wave and THz radiation as a reliable measurement tool in spectroscopy and remote-sensing requires accurate beam characterization. Gaussian approximation is a practical model to describe the radiated beam of Laser sources and high-directivity THz/mm-wave horn antennas. The radiated beam is analytically studied in this paper and a simple closedform formula is presented for the wave-front phase distribution. Analytical results are compared with measurements and good agreement is observed for mm-wave horns. The closed-form formula is used for a parametric error-analysis and uncertainty evaluation as needed in RF metrology. Therefore, the contribution of all the source characteristics and its geometrical parameters to the phase deviation can be shown.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Analytical study of mm-wave and THz beams, application to RF metrology

Kazemipour

Kleine‐Ostmann

Schräder

2013

2013 Asia-Pacific Microwave Conference Proceedings (APMC)

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“…Our HWS has been carefully designed by combining the spatial resolution with the wavefront sensitivity and well calibrated with a sensitivity of less than 14 mrad and a dynamic range of 0.2 rad. 8 The measured accuracy of the wavefront is better than 0.5k 0 . The Hartmann mask is based on a 0.2 mm thick copper plate whereby the holes in the array are 1 mm in diameter and have 3 mm in periodicity.…”

Section: -mentioning

confidence: 86%

“…4(c) that combines the centriods of all the 9 images and summarizes a complete extracted spot field. 8 The wavefront is reconstructed from the extracted spot field by using Zonal wavefront estimation, and the result is shown in Fig. 4(d).…”

Section: -mentioning

confidence: 99%

“…7 However, the phase of the QCL beam has never been directly measured. The wavefronts, containing the phase information, have recently been studied using the Hartmann wavefront sensor (HWS) for a beam generated by a few designed phase objects using a Far Infrared (FIR) gas laser as the THz source 8 and for a beam generated by two focused lenses using a QCL as the source. 9 Until now, the intrinsic wavefront of a 3rd-order DFB QCWL has never been reported.…”

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confidence: 99%

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Beam and phase distributions of a terahertz quantum cascade wire laser

Cui

Hovenier

Ren

et al. 2013

Applied Physics Letters

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We report on both measurements and simulations of the beam profile and wavefront of a singlemode, 3.5 THz quantum cascade wire laser, incorporating a lateral corrugated metal-metal waveguide, 3rd-order distributed feedback grating. The intrinsic wavefront was measured by using a Hartmann wavefront sensor (HWS) without any optical components between the laser and HWS. Both beam profile and wavefront were simulated using an antenna array model, but taking the nonuniform electric field distribution along the waveguide into account. The results show that the nonuniform distribution along the wire laser plays a crucial role in realizing a nearly single-lobed narrow beam. The measured wavefront is spherical and agrees well with the simulation. 1-3 incorporating a lateral corrugated metal-metal waveguide, 3rd-order distributed feedback (DFB) grating are attractive for applications because of their high-temperature operation, low operating power, controllable single-mode emission, mW output power, and single-lobed low divergent beam. In particular, the high-temperature operation and low operating power take advantage of the low-loss double metal waveguide wire laser with a sub-wavelength transverse dimension. The robust single-mode emission is extracted efficiently from the active region of GaAs/AlGaAs by a 3rd-order Bragg grating. Promising 3rd-order DFB QCWLs that deliver single-mode output power of more than 1.5 mW have been demonstrated at 3.5 THz. These QCWLs can be operated in CW mode up to 110 K, but consume less than 300 mW DC power.2 3rd-order DFB QCWLs have further been demonstrated as local oscillators in heterodyne spectrometers centered at 3.5 THz and 4.7 THz, respectively. 4,5 To overcome the diffraction limit of THz sub-wavelength wire lasers, an antenna model has been proposed and a narrow far-field beam was predicted if the longitudinal phase velocity within the laser matches the one in the free-space. 6 However, it is only recently that such a beam has been realized for THz QCWLs by using a 3rd-order lateral corrugated grating, 2 which is equivalent to a periodic array of apertures along the waveguide with a periodicity of roughly half of the free-space wavelength k 0 . One can then apply an end-fire antenna array model. The narrow beam was a result of the radiation added constructively from all the apertures. Interestingly, the observed narrow, single-lobed beams were apparently better than model calculations. The latter show the clear presence of side lobes. Another approach to realize a low divergent beam is to have a similar 3rd-order DFB grating, but adding additional contact fins to achieve the perfect phase-match. The perfect phase matching allows many more periods ($151 periods) that resulted in a narrow main beam. 3 It is known that both intensity and phase distributions of a beam are crucial for optimizing its propagation and beam matching in an optical system. The beam intensity profile has been recognized as one of the important performances for THz quantum cascade lasers (QCLs), reflected ...

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Single-scan multiplane phase retrieval with a radiation of terahertz quantum cascade laser

et al. 2022

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Terahertz phase retrieval from a set of axially separated diffractive intensity distributions is a promising single-beam computational imaging technique that ensures the obtention of high spatial resolutions and phase wavefronts, but remains restricted by time-consuming data acquisition processes. In this work, we have adopted an approach, relying on the radiation of a quantum cascade laser and the implementation of an express single-scan measurement of intensity distributions through the continuous on-the-go displacement of a high-sensitivity antenna-coupled microbolometer sensor array. In addition to the simplicity of this practical implementation and the minimization of measurement times, such an approach overcomes the problem of preliminary optimal selections of transverse intensity distributions used in the iterative phase retrieval algorithm and guarantees the required data diversity for high-quality wavefront reconstruction.

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Terahertz wavefronts measured using the Hartmann sensor principle

Cited by 12 publications

References 26 publications

Analytical study of mm-wave and THz beams, application to RF metrology

Analytical study of mm-wave and THz beams, application to RF metrology

Beam and phase distributions of a terahertz quantum cascade wire laser

Single-scan multiplane phase retrieval with a radiation of terahertz quantum cascade laser

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