The high-performance phototransistor based on two-dimensional materials is very attractive in integrated logic function chips and large-scale real-time optical imaging. Recently, graphene-semiconductor composite film phototransistors have already achieved ultrahigh photoconductive gain due to the strong absorption capacity of the semiconductor layer and the strong mobility of graphene. However, low absorption and high dark current limit the photoresponsivity and detective band of the graphene phototransistors. Here, we fabricate a graphene/C60/Sb composite film photo transistor with a broadband response (450 nm - 1500 nm), fast response speed (20 ms) and ultrahigh peak photoresponsivity (3.927 × 105 A/W). The charge transfer mechanism between layers of the device has been analyzed by adjusting Sb layer thicknesses (5 nm, 10 nm, 20 nm). In addition, we observe the positive and negative photocurrent response in the experiment and study the bidirectional response of the device by applying different gate voltages. The ultrathin phototransistor (10 - 20 nm) is compatible with the traditional CMOS and nanoimprinting process to achieve large area and high-precision array integrated devices.
DNA methylation is one of the earliest known modification pathways, and it regulates gene expression, which in turn influences many biological processes. Direct, label-free detection of DNA methylation with high sensitivity remains a great challenge. Surface-enhanced Raman scattering (SERS), a non-invasive and label-free vibration spectroscopy technique, offers sensitive intrinsic chemical information that makes it an attractive option for DNA analysis. In this study, we employed iodide-modified silver nanoparticles to generate highly consistent SERS signals of DNA at micromolar concentrations in aqueous solutions. This enabled the acquisition of single-base sensitive DNA fingerprint details pertaining to base methylations (such as 5-methylcytosine). As a proof of concept, the SER spectra of a DNA and its methylated counterpart were compared and analyzed, resulting in an obvious identification of DNA methylation. In particular, we first designed two DNA sequences, the sole change being that one of the nucleotides, cytosine, is replaced with a 5-methylcytosine. Further SERS experimental study revealed that methylating a single cytosine in the DNA strand caused a subtle but evident alteration in the SERS spectrum. A new Raman peak emerged at 760 cm-1 the Raman peak at 792 cm-1 moved to 790 cm-1, and there was a noticeable drop in the peak intensity ratio between 1572 cm-1 and 1634 cm-1. This approach may provide a novel and easy-to-use tool for the label-free identification of single-molecule DNA mutations or modifications, furthering the advancement of ultra-sensitive genomic research in the future.
The superlens with plasmonic material have important features such as evanescent wave enhancement and subwavelength imaging. However, the intrinsic loss of the material severely limits the resolution and imposes more stringent requirements on imaging conditions. In this work, we discuss the influence of different temporal features on imaging resolution. The exponential illumination corresponds to a definite imaging state, higher imaging resolution can be obtained with greater exponential decay rate of illumination pulse. This conclusion provides a reference for the selection of pulse time-domain waveforms. In addition, we use this method for periodic pattern imaging, validating its potential for practical applications.
Polarized light has various applications in industrial inspection, remote sensing, and other fields. Traditional methods for detecting polarized light typically rely on the polarization properties of optical components or specific materials to detect and analyze light with different polarization states. However, the polarization detection system designed by these methods has a complex optical path, resulting in bulky size and high cost in large-scale integrated applications, thus hindering the development and application of polarization detection. Therefore, it is crucial to develop polarization detectors to meet the requirements of compact and highly integrated optical devices. The optical catenary structure is a kind of continuous metasurface structure, which has continuous, linear phase change and abundant electromagnetic modes. To further miniaturize the polarization detector for on-chip applications, a potential approach is to combine silicon waveguide with metasurface to achieve a compact, high-efficiency polarization detector. In this work, the on-chip beam polarization detector is effectively realized by using one single catenary gold nanostructure loaded atop silicon on an insulator (SOI) waveguide, which is optimized by the Particle Swarm Optimization algorithm. We envision that our finding could facilitate the application of polarization-optical devices and systems in various fields, including sensing, optical communications, imaging, quantum sciences, etc.
In recent years, the super-oscillatory lens based on optical super-oscillatory phenomenon has been successfully applied to sub-diffraction focusing and imaging. However, most of the previously reported super-oscillatory lens only work in the visible and near-infrared wavelengths, and little research has been done in the ultraviolet. In this paper, a polarization-insensitive ultraviolet super-oscillatory metalens doublet is proposed. The simulation results show that sub-diffraction focusing and imaging with different incidence angles can be achieved at the ultraviolet operating wavelength of 365nm, and the full width at half maximum of the sub-diffraction foci is approximately 0.7 times of the diffraction limit. This metalens doublet has a numerical aperture of 0.4472, a focal length of 0.6896 mm, and a field of view of ±25°. The proposed polarization-insensitive ultraviolet super-oscillatory metalens doublet can be used in the fields of ultraviolet lithography and microscopic imaging.
In this paper, we report a stable processing method to farbricate the nickel disc and polycarbonate(PC) disc with massive character code and address code in a ϕ120mm master disc. Currently, the optimum laser intensity is found to be 45% for exposure step. The micropore size remains the same size during the electroplating indicating the excellent stability and reliability of the process. In addition, the demolding process during the production of optical disc is smooth due to the controlled angle between photoresist and nickel surface. However, the height of microstructure boss on the optical disc after injection molding is about 10-15nm smaller than we expected.
The geometric phase concept has profound implications in many branches of physics, from condensed matter physics to quantum systems. Although geometric phase has a long research history, novel theories, devices, and applications are constantly emerging with developments going down to the subwavelength scale. Specifically, as one of the main approaches to implement gradient phase modulation along a thin interface, geometric phase metasurfaces composed of spatially rotated subwavelength artificial structures have been utilized to construct various thin and planar meta-devices. In this paper, we first give a simple overview of the development of geometric phase in optics. Then, we focus on recent advances in continuously shaped geometric phase metasurfaces, geometric–dynamic composite phase metasurfaces, and nonlinear and high-order linear Pancharatnam–Berry phase metasurfaces. Finally, conclusions and outlooks for future developments are presented.
We design a simple catenary metasurface with high efficiency, which could obtain both the degree of circular polarization and the wavelength of incident polarized light by measuring the diffraction intensity and the deflection angle. The catenary decomposes the incidence into left and right circularly polarized light and diffracts them to different predesigned directions with different deflection angles that present the wavelength information. The diffraction efficiency of the designed catenary exceeds 94%, the average diffraction efficiency is up to 97.6% at the wavelength of 8-14μm, and angular dispersion is 0.078°/nm. Moreover, the degree of circular polarization for various incident polarization states can be characterized by diffraction intensities. This work may provide extensive applications for biosensing, DNA structural analysis, stereochemistry, etc.
Super-oscillation phenomenon provides an effective solution for realizing far-field non-invasive super-resolution imaging. However, most super-oscillatory lenses are challenging to balance the working bandwidth and working efficiency, which greatly limits the practical applications of super-oscillation lenses in optical systems. In this work, a broadband high-efficiency super-oscillatory metalens for sub-diffraction focusing about 0.75 times the diffraction limit based on the reflective metasurface is proposed for super-resolution imaging in the visible ranging from 400 nm to 700 nm. Moreover, another metalens with a sub-diffraction focusing spot equal to 0.6 times of the diffraction limit is also designed to prove the universal applicability of the proposed method. The proposed method provides an effective pathway for the development of microscopy, holography, and machine vision.
In this paper, we report the influence of laser intensity on small dimensions of the microstructure for both exposure of graphic zone and blank zone. Also, the one-time electroplate technology and the two-time electroplate technology were conducted for production of optical discs. A series of laser intensities (30mW, 30%, 35%, 40%, 45%, 50%, 55%) are conducted through laser direct writing. The micropore size increased with the laser intensity for exposure of graphic zone to the laser which leaving holes on the surface of master disc, while the micropore size decreased with laser intensity for exposure of blank zone which leaving bosses on the surface master disc. Moreover, the optimum laser intensity is found to be 45% for both one-time electroplating and two-time electroplating. The micropore size remains the same size during the whole process indicating the excellent stability and reliability of the process. In addition, the demolding process during the production of optical disc is smooth due to the controlled angle between photoresist and nickel surface. However, the height of microstructure boss on the optical disc after injection molding depended on the size of the microstructure. The height of the boss was 150nm for 2μm zone while it was only 80nm for 1μm zone. This work proves the feasibility and potential use of a new physical format for long-life holographic storage disc, which may break monopolies in optical storage field, by applying one-time electroplating and two-time electroplating method.
In this work, we report the influence of laser intensity, via laser direct writing focus on a photoresist, on the different dimensions of the microstructure. A series of laser intensities (30mW, 30%, 35%, 40%, 45%, 50%, 55%) are conducted and the reaction mechanism between laser and photoresist is also proposed. The microstructure size increased with laser intensity and the optimum laser intensity is found to be 45% for both 2μm and 4μm microstructure. The micropore size remains the same size during the whole process (master disc-nickel disc-son disc) indicating the excellent stability and reliability of the process. Additionally, the demolding process during the production of son disc is smooth due to the controlled angle between Ni base surface and photoresist. This work proves the feasibility and compatibility of the production of a new physical format for long-life holographic storage disc, which significantly increase the storage density, access speed and shelf life compared to traditional disc, by applying traditional processing method (master disc-Ni discson disc).
Dielectric metasurfaces is a plane optical device to achieve the desired function by modulating amplitude and phase, polarization for the incident light, and its transmission efficiency is higher than other metasurfaces, these advantages lead to dielectric metasurfaces will be used widely in the future. Nevertheless, the majority of metasurfaces are planar singlelayered structure, which limit seriously the view field and effect of monochromatic imaging. Here, we demonstrate a composed dielectric meta-lens doublet by the electromagnetic simulation can achieve perfectly diffraction-limited monochromatic focus for the polarization-insensitive incident lights at a wavelength of 375 nm, which has the view field of 60°, the numerical aperture of 0.5, and a focal length of 380μm. Due to the dielectric meta-lens doublet has the scaling of subwavelength at ultraviolet light, and the devices have high distinguishability, it can be used widely in nanolithography, imaging with large view field, and other optical domains.
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