All-dielectric metalens for terahertz wave imaging

Jiang, Xue; Chen, Hao; Li, Zeyu; Yuan, Hongkuan; Cao, Luyao; Luo, Zhenfei; Zhang, Kun; Zhang, Zhihai; Wen, Zhongquan; Zhu, Li-Guo; Zhou, Xun; Liang, Gaofeng; Ruan, Desheng; Du, Liang-Hui; Wang, Lingfang; Chen, Gang

doi:10.1364/oe.26.014132

Cited by 63 publications

(23 citation statements)

References 37 publications

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“…The first experiment was conducted for single frequency focusing performance (the experimental method can be found in Section S3, Supporting Information). Because the linearly polarized wave is a superposition of the RCP wave and the LCP wave, [81,89,90] its LCP component can be focused by the proposed metalens. In the experiment, the QCL was operated in single longitudinal mode at a drive current of 650 mA and a heatsink temperature of 20 K. Figure 6a shows the measured emission spectrum of the QCL lasing at 2.54 THz (λ = 118.11 µm) obtained by an Fourier-transform-infrared spectrometer (Vertex 80v, Bruker Corporation).…”

Section: Resultsmentioning

confidence: 99%

“…In certain cases, the super‐resolution optical fields can be treated as the result of constructive interference, which involves a serial of plane waves with high spatial frequencies. In the proposed method, the phase profile of the metalens adopts the commonly used hyperbolic profile [ 81,82 ] to ensure a constructive interference at the focus, as given in Equation ()

\begin{matrix} φ (r, λ_{0}) = 2 π n - (\sqrt{r^{2} + f^{2}} - \sqrt{R_{lens}^{2} + f^{2}}) \frac{2 π}{λ_{0}} \end{matrix}

where r is the radial coordinate, λ 0 is the working wavelength, f is the focal length, R lens is the lens radius, and n is the integer.…”

Section: Theoretical Considerationmentioning

confidence: 99%

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Broadband Achromatic Sub‐Diffraction Focusing by an Amplitude‐Modulated Terahertz Metalens

Zhao

Dai

et al. 2020

Advanced Optical Materials

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THz focusing and imaging include bulky dielectric refractive lenses and parabolic mirrors. Due to the diffraction effect, the resolution of conventional optics is limited by the Abbe diffraction limit (DL) of 0.5λ/NA, [5] where λ and NA are working wavelength and numerical aperture (NA), respectively. Recently, there has been a growing interest in developing far-field super-resolution optical devices, which can achieve point-spread-function (PSF) of size smaller than the Abbe DL without evanescent waves [6] at a distance far beyond the near-field regime. [7,8] Based on the concept of superoscillation, [9-11] a variety of sub-diffraction or super-resolution optical devices have been demonstrated either theoretically or experimentally, including scalar super-resolution metalenses [12-22] and vector super-resolution metalenses. [23-33] Such super-resolution devices have been successfully shown great potential in labelfree super-resolution microscopy [13,21,34,35] and super-resolution telescope. [36] However, most previously reported super-resolution metalenses only work at one single wavelength [37] or several designed discrete wavelengths, [38,39] while broadband achromatic metalenses working in the visible [40-42] and nearinfrared spectrum [43-46] as well as THz regime [47] are restricted by the Abbe DL. To achieve a broadband super-resolution imaging, recently, a broadband super-resolution scheme was proposed and experimentally demonstrated by adopting the combination of a super-oscillatory binary phase filter and a conventional bulk achromatic refractive convex lens. [48] Up to now, it is still a great challenge to realize a sub-diffraction achromatic metalens with a continuous broad bandwidth. To achieve broadband achromatic super-resolution focusing, similar to the conventional optics, dispersion compensation is required to ensure that the wave of different wavelengths is focused at the same focal point. In addition, wave front engineering is also required to achieve the super-resolution PSF. Recent fast development of metasurfaces [49-54] provides effective ways to manipulate the amplitude, [55,56] phase, [57-61] polarization [30,33,62-66] and dispersion properties [67,68] of light waves. To achieve wave front shaping without influences on dispersion, one possible way is to realize broadband achromatic super-resolution by adopting amplitude modulation. Conventionally, pupil filters [69-78] can be used to achieve super-resolution in traditional optical systems. Recently, there are growing interests in developing super-resolution metalenses for applications of focusing and imaging. On one hand, various sub-diffraction metalenses have been demonstrated; however, most of them only work at a single wavelength or multiple discrete wavelengths. On the other hand, the previously reported broadband achromatic metalenses are diffraction-limited, or their focal spots are larger than the corresponding Abbe diffraction limit, 0.5λ/NA, where λ and NA are the lens working wavelength and numerical aperture. In the present wo...

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Section: Resultsmentioning

confidence: 99%

\begin{matrix} φ (r, λ_{0}) = 2 π n - (\sqrt{r^{2} + f^{2}} - \sqrt{R_{lens}^{2} + f^{2}}) \frac{2 π}{λ_{0}} \end{matrix}

where r is the radial coordinate, λ 0 is the working wavelength, f is the focal length, R lens is the lens radius, and n is the integer.…”

Section: Theoretical Considerationmentioning

confidence: 99%

Broadband Achromatic Sub‐Diffraction Focusing by an Amplitude‐Modulated Terahertz Metalens

Zhao

Dai

et al. 2020

Advanced Optical Materials

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“…102 Recently, a meta-lens featuring the dielectric metasurface with a subwavelength unit size of 0.39λ was proposed, demonstrating its competitive application in the THz imaging and focusing. 103 In general, thin dielectric films are used in the PCAs predominantly as antireflection coating layers, reducing the Fresnel losses and thereby increasing the absorption of an optical excitation by a photoconductive substrate. The most commonly used materials have become SiO 2 , 60,61 Si 3 N 4 , 104 and Al 2 O 3 .…”

Section: Dielectric Metasurfacesmentioning

confidence: 99%

Metallic and dielectric metasurfaces in photoconductive terahertz devices: a review

et al. 2019

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This review highlights recent and novel trends focused on metallic (plasmonic) and dielectric metasurfaces in photoconductive terahertz (THz) devices. We demonstrate the great potential of its applications in the field of THz science and technology, nevertheless indicating some limitations and technological issues. From the state-of-the-art, the metasurfaces are, by far, able to force out previous approaches like photonic crystals and are capable of significantly increasing the performance of contemporary photoconductive devices operating at THz frequencies.

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“…However, these proposed metasurface functions still pose the challenges of large chromatic aberrations and considerable losses [9,20]. In addition, few experimental works have been reported on efficient terahertz achromatic meta-devices based on all-dielectric metasurfaces [21][22][23].…”

Section: Introductionmentioning

confidence: 99%