Broadband achromatic metalens in terahertz regime

Cheng, Qingqing; Ma, Ming; Yu, Dong; Shen, Zhixiong; Xie, Jingya; Wang, Juncheng; Xu, Na; Guo, Hanming; Hu, Wei; Wang, Shuming; Li, Tao; Zhuang, Songlin

doi:10.1016/j.scib.2019.08.004

Cited by 113 publications

(58 citation statements)

References 40 publications

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“…The theoretically predicted focusing efficiency of 13.01-32.60% in the bandwidth between 2.29 and 2.70 THz, which is comparable with the reported efficiency of 20.0-68.0% of diffraction-limited achromatic metalenses. [40][41][42]44,45,47] The achromatic performance of the proposed metalens has been investigated by using vector angular spectrum method (VASM). [31,86] Figure 3a gives the optical intensity profiles in the X-Z propagation plane at the 11 different wavelengths with equal intervals within the wavelength range from 111 to 131 µm.…”

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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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: 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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“…Furthermore, the resonance can be freely engineered in unit cell design, allowing efficient manipulation of the local phase, amplitude, and polarization on a subwavelength scale, thus controlling the overall spectral response and wavefront of the devices. Typical THz metasurface devices include filters, 13,14 sensors, [15][16][17][18] absorbers, [19][20][21] modulators, [22][23][24][25][26] polarization controllers, 27,28 flat lenses, [29][30][31][32] special beam generators, 33,34 holograms, 29,[35][36][37] cloaks, 38,39 etc. Though much more compact than their traditional counterparts, these metadevices have little effect in reducing the size of the THz propagation path in the systems.…”

Section: Introductionmentioning

confidence: 99%

Terahertz surface plasmonic waves: a review

et al. 2020

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Terahertz science and technology promise many cutting-edge applications. Terahertz surface plasmonic waves that propagate at metal-dielectric interfaces deliver a potentially effective way to realize integrated terahertz devices and systems. Previous concerns regarding terahertz surface plasmonic waves have been based on their highly delocalized feature. However, recent advances in plasmonics indicate that the confinement of terahertz surface plasmonic waves, as well as their propagating behaviors, can be engineered by designing the surface environments, shapes, structures, materials, etc., enabling a unique and fascinating regime of plasmonic waves. Together with the essential spectral property of terahertz radiation, as well as the increasingly developed materials, microfabrication, and time-domain spectroscopy technologies, devices and systems based on terahertz surface plasmonic waves may pave the way toward highly integrated platforms for multifunctional operation, implementation, and processing of terahertz waves in both fundamental science and practical applications. We present a review on terahertz surface plasmonic waves on various types of supports in a sequence of properties, excitation and detection, and applications. The current research trend and outlook of possible research directions for terahertz surface plasmonic waves are also outlined.

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“…More recently, inspired by achromatic metalens designs in the visible and near-IR range, [26][27][28][29][30] broadband achromatic focusing has been realized in the THz regime via dispersive phase compensation from C-shape silicon micropillar arrays. 31 By contrast, for spectrographic and tomographic applications, 32,33 large chromatism is favored to separate focal spots of different frequencies spatially without crosstalk. 34,35 If dynamic alternation between the achromatic and dispersive focusing properties can be achieved using a single metalens, it would greatly promote the practical applications of spectroscopy and imaging systems.…”

Section: Introductionmentioning

confidence: 99%

Liquid crystal integrated metalens with tunable chromatic aberration

Shen

Zhou

et al. 2020

Adv. Photon.

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Overcoming chromatic aberrations is a vital concern in imaging systems in order to facilitate fullcolor and hyperspectral imaging. By contrast, large dispersion holds opportunities for spectroscopy and tomography. Combining both functions into a single component will significantly enhance its versatility. A strategy is proposed to delicately integrate two lenses with a static resonant phase and a switchable geometric phase separately. The former is a metasurface lens with a linear phase dispersion. The latter is composed of liquid crystals (LCs) with space-variant orientations with a phase profile that is frequency independent. By this means, a broadband achromatic focusing from 0.9 to 1.4 THz is revealed. When a saturated bias is applied on LCs, the geometric phase modulation vanishes, leaving only the resonant phase of the metalens. Correspondingly, the device changes from achromatic to dispersive. Furthermore, a metadeflector with tunable dispersion is demonstrated to verify the universality of the proposed method. Our work may pave a way toward active metaoptics, promoting various imaging applications.

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Broadband achromatic metalens in terahertz regime

Cited by 113 publications

References 40 publications

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

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

Terahertz surface plasmonic waves: a review

Liquid crystal integrated metalens with tunable chromatic aberration

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