Toraldo filters with concentric unequal annuli of fixed phase by evolutionary programming

Reza, N.; Hazra, Lakshminarayan

doi:10.1364/josaa.30.000189

Cited by 22 publications

(8 citation statements)

References 35 publications

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“…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. In the present work, an approach of realizing broadband achromatic sub‐diffraction focusing has been proposed utilizing both dispersion engineering and amplitude modulation.…”

Section: Introductionmentioning

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: Introductionmentioning

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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“…This task has been addressed for amplitude masks [ 20 , 30 , 31 ], however, it has only limited applications to Toraldo-style phase masks [ 16 , 17 ]. While genetic algorithm have been implemented to optimize Toraldo-style phase masks in the paraxial limit [ 15 ], these calculations are insufficient for applications using strongly focused fields.…”

Section: Theorymentioning

confidence: 99%

“…Therefore the phase mask should be chosen for the specific application. While more complicated excitation masks can be used, the width of the centroid cannot be significantly reduced by going beyond a single π phase step [ 15 ].…”

Section: Theorymentioning

confidence: 99%

“…The simplest example of this type of mask is a single π phase step, where the diameter of the π phase step determines the width of the centroid. While this type of phase mask has been extensively explored theoretically in the paraxial limit [ 11 – 15 ], investigating full theoretical foundation for strongly focused non-paraxial beams has been limited [ 16 , 17 ]. In addition, the substantial side lobes in the focus generated by the phase mask have limited the experimental realizations for superresolution imaging.…”

Section: Introductionmentioning

confidence: 99%

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Phase Mask-Based Multimodal Superresolution Microscopy

et al. 2017

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We demonstrate a multimodal superresolution microscopy technique based on a phase masked excitation beam in combination with spatially filtered detection. The theoretical foundation for calculating the focus from a non-paraxial beam with an arbitrary azimuthally symmetric phase mask is presented for linear and two-photon excitation processes as well as the theoretical resolution limitations. Experimentally this technique is demonstrated using two-photon luminescence from 80 nm gold particle as well as two-photon fluorescence lifetime imaging of fluorescent polystyrene beads. Finally to illustrate the versatility of this technique we acquire two-photon fluorescence lifetime, two-photon luminescence, and second harmonic images of a mixture of fluorescent molecules and 80 nm gold particles with > 120 nm resolution (λ/7). Since this approach exclusively relies on engineering the excitation and collection volumes, it is suitable for a wide range of scanning-based microscopies.

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“…For example, Toraldo-style phase mask (Francia, 1952) has been introduced in confocal scanning microscopy to produce the focus with a narrower central spot. Researchers have conducted theoretical researches on this phase mask in both paraxial limit (Gao, Gan, & Xu, 2007;Luo & Zhou, 2004;Reza & Hazra, 2013;Sheppard, Calvert, & Wheatland, 1998;Sheppard, Campos, Escalera, & Ledesma, 2008) and non-paraxial area (Kim, Bryant, & Stranick, 2012;Raghunathan & Potma, 2010). However, the energy in sidelobes would be increased if the Toraldo-style phase mask was used to modulate the excitation beam.…”

Section: Introductionmentioning

confidence: 99%

Light sheet microscopy with high spatial resolution based on polarized structured illumination beam modulated by the phase mask

Wang

Liu

et al. 2018

Microscopy Res & Technique

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In this article, we present a method to improve axial resolution and expand the field of view of conventional light sheet fluorescence microscopy (LSFM) by phase modulation of the illumination beam. We added a bisected annular binary phase mask on the illumination path to modulate the radially polarized beam. The central spot of the modulated point spread function is narrower than that of Gaussian focus, although the sidelobe energy is increased. Then, a diffraction grating is used to produce multiple copies of this illumination pattern, and these pattern copies form the light sheet. By matching the numerical apertures of illumination lens and detection lens, the sidelobes on the detection axis can be suppressed in the captured data, although they do still contribute to photobleaching and phototoxicity in the sample. The simulation results show that the proposed method effectively reduces the thickness of the light sheet by 1.3 times, and increase the length of the light sheet by two times compared with conventional LSFM.

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Toraldo filters with concentric unequal annuli of fixed phase by evolutionary programming

Cited by 22 publications

References 35 publications

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

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

Phase Mask-Based Multimodal Superresolution Microscopy

Light sheet microscopy with high spatial resolution based on polarized structured illumination beam modulated by the phase mask

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