Search

Polaritons - material excitations coupled with light - are thought to hold the potential for the extreme control of light down to the atomic length-scale because of their high field...

Aiming to further improve the resolution and quality of plasmonic lithography, a self-aligned patterning technique is introduced to it to obtain ultrafine nanopatterns with high contrast and low line edge error (LER). By improving the line edge roughness of the initial plasmonic lithography patterns, 16 nm half-pitch surface nanostructures with a height of 70 nm can be obtained. Moreover, with the help of plasma etching and atomic layer deposition in this process flow, the LER of the 16 nm half-pitch surface nanostructure can achieve 1.3 nm. Further application indicates that this process can also be used to fabricate nanoholes with the feature size as small as 9 nm. This approach provides a new perspective on the manufacture of surface nanostructures with ultrahigh resolution and high aspect ratios, which would find potentially promising applications in metal–air transistors, biosensors, DNA sequencing, etc.

In this paper, efficient ultra-broadband absorption from ultraviolet (UV) to near infrared (NIR) is achieved using a metamaterial perfect absorber (MPA) with refractory constituents. Both simulated and experimental results indicate that this proposed MPA exhibits an average absorption over 95% at wavelengths ranging from 200 nm to 900 nm. Besides, owing to the ultrathin thickness and symmetrical topology of this device, it exhibits great angular tolerance up to 60° independent of the incident polarizations. Excellent thermal stability is also demonstrated at high operation temperatures. The physical origin of the ultra-broadband characteristics is mainly based on diffraction/interference engineering at short wavelengths and the anti-reflection effect at long wavelengths. We believe that such a device may find potential applications ranging from photodetection and photothermal energy conversion to ultraviolet protection and thermophotovoltaics.

Controlling the propagation direction of surface plasmon polaritons (SPPs) at will using planar structures has been investigated in recent years. However the realization of a high extinction ratio of a SPP directional launcher in a densely integrated and miniaturized way, especially at the wavelength scale, still remains a challenge. To the best of our knowledge, the maximum value of the extinction ratio of a unidirectional SPP launcher based on the planar metasurface in experiment is nearly 250, which relies on the combined effect of several gap-plasmon resonator blocks with a lateral dimension much larger than the incident wavelength. Here, we design and experimentally demonstrate a polarization-controlled unidirectional SPP launcher based on a single column catenary aperture array with a lateral dimension as small as 552 nm, which is even smaller than the working wavelength. Under the illumination of circularly polarized light, our designed SPP launcher exhibits a simulated extinction ratio reaching up to 495 at a wavelength of 618 nm and 283 in the experiment. The compact size and distinctive extinction ratio may pave a new way for the directional excitation of SPPs and can be useful in compact plasmonic circuits and other photonic integrated devices.

The past decade has witnessed a great deal of optical systems designed for exceeding the Abbe's diffraction limit. Unfortunately, a deep subwavelength spot is obtained at the price of extremely short focal length, which is indeed a near-field diffraction limit that could rarely go beyond in the nanofocusing device. One method to mitigate such a problem is to set up a rapid oscillatory electromagnetic field that converges at the prescribed focus. However, abrupt modulation of phase and amplitude within a small fraction of a wavelength seems to be the main obstacle in the visible regime, aggravated by loss and plasmonic features that come into function. In this paper, we propose a periodically repeated ring-disk complementary structure to break the near-field diffraction limit via plasmonic Fano resonance, originating from the interference between the complex hybrid plasmon resonance and the continuum of propagating waves through the silver film. This plasmonic Fano resonance introduces a pi phase jump in the adjacent channels and amplitude modulation to achieve radiationless electromagnetic interference. As a result, deep subwavelength spots as small as 0.0045 lambda(2) at 36 nm above the silver film have been numerically demonstrated. This plate holds promise for nanolithography, subdiffraction imaging and microscopy.

Composed of ultrathin metal or dielectric nanostructures, metasurfaces can manipulate the phase, amplitude and polarization of electromagnetic waves at a subwavelength scale, which is promising for flat optical devices. In general, metasurfaces composed of space-variant anisotropic units are sensitive to the incident polarization due to the inherent polarization dependent geometric phase. Here, we implement polarization-independent broadband metasurface holograms constructed by polarization-dependent anisotropic elliptical nanoholes by elaborate design of complex amplitude holograms. The fabricated meta-hologram exhibits a polarization insensitive feature with an acceptable image quality. We verify the feasibility of the design algorithm for three-dimensional (3D) meta-holograms with simulation and the feasibility for two-dimensional (2D) meta-holograms is experimentally demonstrated at a broadband wavelength range from 405 nm to 632.8 nm. The effective polarization-independent broadband complex wavefront control with anisotropic elliptical nanoholes proposed in this paper greatly promotes the practical applications of the metasurface in technologies associated with wavefront manipulation, such as flat lens, colorful holographic displays and optical storage.

Nanofabrication technology with high-resolution, high-throughput and low-cost is essential for the development of nanoplasmonic and nanophotonic devices. At present, most metasurfaces are fabricated in a point by point writing manner with electron beam lithography or a focused ion beam, which imposes a serious cost barrier with respect to practical applications. Near field optical lithography, seemingly providing a high-resolution and low-cost way, however, suffers from the ultra shallow depth and poor fidelity of obtained photoresist patterns due to the exponential decay feature of evanescent waves. Here, we propose a method of surface plasmonic imaging lithography by introducing a reflective plasmonic lens to amplify and compensate evanescent waves, resulting in the production of nano resist patterns with high fidelity, contrast and enhanced depth beyond that usually obtained by near field optical lithography. As examples, a discrete and anisotropically arrayed nano-slots mask pattern with different orientations and a size of 40 nm × 120 nm could be imaged in photoresist and transferred successfully onto a metal layer through an etching process. Evidence for the pattern quality is given by virtue of the fabricated metasurface lens devices showing good focusing performance in experiments. It is believed that this method provides a parallel, low-cost, high-throughput and large-area nanofabrication route for fabricating nanostructures of holograms, vortex phase plates, bio-sensors and solar cells etc.

For the miniaturization of optical holographic and data recording devices, large information capacity or data density is indispensable but difficult to obtain using traditional technologies. In this paper, an ultrahigh-capacity metasurface hologram is proposed by encoding information in deep-subwavelength scale nanohole arrays, which can be reconstructed via a light beam with proper designed incident angles. The imaging information capacity of the two-dimensional (2D) hologram, defined by the distortion-free region, can be increased 11.5 times, which is experimentally demonstrated by focused ion beam (FIB) milling of an ultrathin metallic film. We also prove the feasibility of a three-dimensional (3D) hologram of spiral lines designed by using the point source algorithm. Benefitting from the ultrahigh capacity of the deep-subwavelength metasurface, dynamic holographic displays can be realized by controlling the incident angle. The method proposed here can also be leveraged to achieve large capacity optical storage, colorful holographic displays, lithography technology etc.

Nanoapertures with space-variant geometries are designed in a gold thin film to construct an ultrathin plasmonic metasurface, which has been demonstrated both numerically and experimentally to selectively generate and focus orbital angular momentum (OAM) beams with different topological charges at the wavelengths of 930 nm and 766 nm, respectively. Moreover, the interference patterns between the different circularly polarized transmission light were used to confirm the topological charges unambiguously. The agreement between the simulated and measured results suggests that the metasurface of wavelength-selective OAM modes may have potential applications in future optical communication systems.