Refractive Behavior Research Articles

High-efficiency wide-angle anomalous refraction with acoustic metagrating

Abstract The emergent metagrating, with its unique and flexible beam shaping capabilities, offers new paths to efficient modulation of acoustic waves. In this work, an acoustic metagrating is demonstrated for high-efficiency and wide-angle anomalous refraction. It is shown that the normal reflection and transmission can be totally suppressed by properly modulating the amplitude and phase characteristics of the metagrating supercells for high-efficiency anomalous refraction. The anomalous refraction behavior is achieved in the wide range of incident angles from 28° to 78°, and the efficiency of -1st order diffraction is higher than 90% by finely designing the metagrating structure. The anomalous refraction behaviors are verified experimentally at incidence angle of 28°, 45° and 78°, respectively. The demonstrated metagrating is anticipated to possess efficient wide-angle composite wavefront engineering applications in such fields as communications.

Structural and ultrafast third-order nonlinearities of methyl and methoxy substituted anthracene chalcones: Z-scan, four-wave mixing, and DFT approaches

We report on the structural, thermal, linear, and ultrafast third-order nonlinear optical (NLO) properties of two novel anthracene chalcones: (2E)-1-(anthracen-9-yl)-3-(5-methylthiophen-2-yl)prop-2-en-1-one (5ML2SANC) and (2E)-1-(9-anthryl)-3-(2,4,5-trimethoxyphenyl)prop-2-en-1-one (245TMANC). The chalcones were synthesized by Claisen-Schmidt condensation reaction, and the single crystals were grown by the solvent evaporation method. The molecular structure was confirmed by FTIR and NMR spectroscopy, while the crystal structure was determined using the single crystal XRD. Both crystals belong to centrosymmetric monoclinic crystal system with space group P21/n. The Hirshfeld surface was analyzed to understand intermolecular interactions, and the band structures - including HOMO-LUMO levels, excited state energies, GCRDs and MEPs-were studied using DFT. The ultrafast third-order NLO properties were investigated by Z-scan and degenerate four-wave mixing (DFWM) techniques using Ti: Sapphire amplifier laser delivering ∼50 fs pulses at 800 nm (1 kHz, ∼4 mJ, 2 W). Two-photon absorption, positive nonlinear refraction, optical limiting and optical switching behaviors were observed by Z-scan measurements. The time-resolved DFWM show that the decay time of 5ML2SANC is ∼127 fs, while for 245TMANC it is ∼142 fs. The second hyperpolarizability (γ) measured by Z-scan, DFWM and the estimations from the DFT theory are found to be in good agreement (∼10−34 esu). The ultrafast optical response, significant NLO properties and thermal stability of the synthesized chalcones demonstrate their potential suitability in optical limiting and switching applications.

Hydrogen storage potential of XNiH3 (X= Sr and Ba) compounds: A comprehensive DFT analysis

The increasing need for sustainable energy solutions emphasizes the significance of effective hydrogen storage materials. This work provides a thorough analysis using density functional theory (DFT) to assess the capacity of XNiH3 (X = Sr and Ba) compounds, where X denotes strontium (Sr) and barium (Ba), for storing hydrogen. We employed the Cambridge Serial Total Energy Package (CASTEP) approach to optimize the geometries and determine the structural, electrical, optical, and mechanical properties of SrNiH3 and BaNiH3. The findings indicate that SrNiH3 demonstrates a higher gravimetric hydrogen storage capacity (2.03 %) in comparison to BaNiH3 (1.52 %). Both compounds exhibit metallic behavior, characterized by the absence of band gaps, which indicates a high level of electrical conductivity. The optical investigations reveal prominent absorption peaks at 25.32 eV for SrNiH3 and 18.82 eV for BaNiH3, accompanied by substantial energy loss functions and refractive behaviors. Based on mechanical studies, it has been determined that both compounds are mechanically stable. However, SrNiH3 exhibits a larger bulk modulus and Young's modulus compared to BaNiH3. The results highlight the potential of SrNiH3 and BaNiH3 as suitable options for storing hydrogen, which can contribute to the progress of clean energy technology.

Physicochemical properties of 2-amino-5-methylpyridinium 3-carboxy-4-hydroxybenzenesulfonate single crystal: An efficient material for optoelectronic applications

A novel third-order organic nonlinear optical (NLO) material with promising excellent properties in the crucial NLO application. For the first time high NLO active 2-amino-5-methylpyridinium 5-sulfosalicylic acid (2A5MP3C4H) has been rationally designed and single crystals have been grown by the slow evaporation solution growth technique (SEST). X-ray diffraction analysis revealed that 2A5MP3C4H belongs to the category of triclinic system and has a Centro symmetric space group of P1. Remarkably, the grown crystal exhibits competitive and even superior physical properties including high thermal stability and wider transparency than the standard NLO single crystal. The morphology of the as-grown 2A5MP3C4H crystal was equivalent to the theoretically produced morphology. Fourier transform infrared spectroscopy (FTIR) was used to investigate the molecular vibrations of 2A5MP3C4H. The optical characteristics of 2A5MP3C4H recorded optical transmittance spectrum reveals that the 2A5MP3C4H crystal possesses good optical transparency in the range between ultraviolet (UV) and near-infrared (NIR) regions. Intriguingly, the short cut-off edge of the grown crystal is found to be about 345 nm which is more favourable for developing modern photonic and optoelectronic devices application. The Laser Damage Threshold (LDT), were investigated to understand its effectiveness to be utilized in the area of optoelectronics and photonics. The thermal and mechanical stability of 2A5MP3C4H was tested using Thermo gravimetric Differential Thermal Analysis (TG-DTA) and Vickers hardness test. The third-order nonlinear optical properties of 2A5MP3C4H single crystals were analyzed, which involves studying the absorption coefficient and refractive index behaviour using a continuous wave laser. Additionally, the grown crystal exhibits outstanding third-order NLO response and wide LDT, which are crucial characteristics for developing practical NLO devices. There are various 2-amino-5-methylpyridine (2A5MP) derivative single crystals available in the literature. However 2A5MP3C4H crystal has not been reported earlier. So, we have carried out our researcher on this new novel crystal. Our findings consequently open a novel path for the logical design of enormous, thermally stable and NLO-active organic complexes for true NLO applications.

New Insights on Solvent-Induced Changes in Refractivity and Specific Rotation of Poly(propylene oxide) Systems Extracted from Channeled Spectra.

Investigation of chiroptical polymers in the solution phase is paramount for designing supramolecular architectures for photonic or biomedical devices. This work is devoted to the case study of poly(propylene oxide) (PPO) optical activity in several solvents: benzonitrile, carbon disulfide, chloroform, ethyl acetate, and p-dioxane. To attain information on the interactions in these systems, rheological testing was undertaken, showing distinct variations of the rheological parameters as a function of the solvent type. These aspects are also reflected in the refractive index dispersive behavior, from which linear and non-linear optical properties are extracted. To determine the circular birefringence and specific rotation of the PPO solutions, the alternative method of the channeled spectra was employed. The spectral data were correlated with the molecular modeling of the PPO structural unit in the selected solvents. Density functional theory (DFT) computational data indicated that the torsional potential energy-related to the O1-C2-C3-O4 dihedral angle from the polymer repeating unit-was hindered in solvation environments characterized by high polarity and the ability to interact via hydrogen bonding. This was in agreement with the optical characterization of the samples, which indicated a lower circular birefringence and specific rotation for the solutions of PPO in ethyl acetate and p-dioxane. Also, the shape of optical rotatory dispersion curves was slightly modified for PPO in these solvents compared with the other ones.

Ingenious Modulation of Third-Order Nonlinear Optical Response of Zr-MOFs through Defect Engineering Based on a Mixed-Linker Strategy.

Defect engineering plays a pivotal role in regulating electronic structure and facilitating charge transfer, yielding captivating effects on third-order nonlinear optical (NLO) properties. In this work, we utilized a mixed-linker strategy to intentionally disrupt the initial periodic arrangement of UiO-66 and construct defects. Specifically, we incorporated tetrakis(4-carboxyphenyl)porphyrin (TCPP) with an exceptionally electron-rich delocalization system into the framework of UiO-66 using a one-pot solvothermal method, ingeniously occupying the partial distribution sites of the Zr6 clusters. Compared to UiO-66, the NLO absorption and refraction performance of TCPP/UiO-66 were significantly improved. Additionally, due to the presence of nitrogen-rich sites that can accommodate metal ions in the porphyrin ring of TCPP, Co(II), Ni(II), Cu(II), and Zn(II) are introduced into TCPP/UiO-66, extending the d-π conjugation effect to further regulate the defects. The NLO absorption behavior transforms saturation absorption (SA) to reverse saturation absorption (RSA), while the refraction behavior shifts from self-defocusing to self-focusing. This work shows that defects can effectively regulate the electronic structure, while TCPP plays a crucial role in significantly enhancing electron delocalization.

Controllable Modulation of Third‐Order NLO Properties by Polymer‐Modified MOFs Core@Shell Nanoarchitecture

AbstractThe delocalization and rearrangement of π electron clouds in space is the crucial source of regulating nonlinear optical (NLO) performance. Herein, a core‐shell metal organic framework (MOF)‐heterojunction is constructed to achieve the effect of tuning NLO properties by promoting charge transfer through multiple interactions between heterogeneous interfaces. [Cd(L)(4,4′‐bpy)(H2O)]n (Cd‐MOF) is selected to coat on polyaniline (PANI) surface to form PANI@Cd‐MOF. The constructed heterojunction displays an enhanced reverse saturation absorption (RSA) signal compared with Cd‐MOF, and it should be noted that the third‐order NLO refractive behavior changes from the self‐defocusing of Cd‐MOF to the self‐focusing of PANI@Cd‐MOF. It is proposed that high‐speed electronic communication bridges established via the rich hydrogen bond network (O… H‐N) and π–π interactions between heterogeneous interfaces can effectively modify the π electron cloud density that finally regulates the NLO properties. This work is believed to provide new avenues and insights for the design of third‐order NLO materials.

Laser-Induced graphene-based Fabry-Pérot cavity label-free immunosensors for the quantification of cortisol

There is a strong and growing need to monitor stress biomarkers in human beings and animals for real-time wellness assessment, which is a key indicator of health. Toward this, we report an optical fiber immunosensor based on laser-induced graphene (LIG) for the potential quantification and monitoring of cortisol hormone. The developed sensors were created using the Fabry-Pérot cavity principle. The cavities were filled with polyimide (PI) and, in some cases, PI mixed with gold nanoparticles. The interferometers were tested for temperature and refractive index, and an increase of two times in the sensitivity to the refractive index was observed due to the addition of the gold nanoparticles. In addition, the PI cavity was partially transformed into LIG using a CO2 20 kHz pulsed laser. The resulting LIG morphology was quite porous and presented a leafy texture. The presence of LIG creates a second cavity within the interferometer, and as a consequence, the spectral response of the interferometers resembled the Vernier effect. The refractive index behavior of the LIG-modified interferometers shows improvements in sensitivity up to 15.3 times due to the creation of the LIG cavity. The interferometers were then functionalized with anti-cortisol to promote an affinity for cortisol. Excellent sensitivities of up to -34.7 ± 0.7 nm/log(ng/mL) were achieved within few ng/mL concentration ranges (within the 0.5 to 3 ng/mL). The results obtained show an increase of up to 50 times in sensitivity when compared with other cortisol sensors. The achieved limit of detection was 0.1 ng/mL for the proposed sensors. The sensors’ responses were also shown to be immune to the interference from substances such as glucose, sucrose, fructose, and ascorbic acid. This study lays the foundation for new cortisol biosensors demonstrating a great potential for detection in a simple and highly sensitive way, opening its path for relevant biomedical and environmental monitoring applications in real samples. As a future outline, selectivity studies employing the detection of cortisol in the presence of interfering agents, both using synthetic and real samples, will be accomplished in order to fully investigate the potential of these sensing tools in real-life scenarios.

Hybrid Approach for Multiscale and Multimodal Time-Resolved Diagnosis of Ultrafast Processes in Materials via Tailored Synchronization of Laser and X-ray Sources at MHz Repetition Rates

The synchronization of laser and X-ray sources is essential for time-resolved measurements in the study of ultrafast processes, including photo-induced piezo-effects, shock wave generation, and phase transitions. On the one hand, optical diagnostics (by synchronization of two laser sources) provides information about changes in vibration frequencies, shock wave dynamics, and linear and nonlinear refractive index behavior. On the other hand, optical pump–X-ray probe diagnostics provide an opportunity to directly reveal lattice dynamics. To integrate two approaches into a unified whole, one needs to create a robust method for the synchronization of two systems with different repetition rates up to the MHz range. In this paper, we propose a universal approach utilizing a field-programmable gate array (FPGA) to achieve precise synchronization between different MHz sources such as various lasers and synchrotron X-ray sources. This synchronization method offers numerous advantages, such as high flexibility, fast response, and low jitter. Experimental results demonstrate the successful synchronization of two different MHz systems with a temporal resolution of 250 ps. This enables ultrafast measurements with a sub-nanosecond resolution, facilitating the uncovering of complex dynamics in ultrafast processes.

Refractive surgery to correct visual impairments in 267 children with autism spectrum and related neuro-developmental disorders: improvements in vision and behavior.

Children with autism spectrum disorder (ASD) may have impaired vision owing to high refractive errors and aversion to spectacles or contact lenses. Visual blurring is caused by near-sighted myopia, far-sighted hyperopia, or astigmatism in one or both eyes. Refractive surgery can restore sharp vision and eliminate the need for spectacles and contact lenses. Restoration of sharp vision may improve ASD behavior. We aimed to determine the refractive outcomes in this cohort using ophthalmic measures and behavioral and school performance alterations after refractive surgery by employing parent-proxy reports. This interventional, retrospective case series included data from 267 children with refractive errors and neurodevelopmental disorders (NDDs) diagnosed as ASD alone or NDD with ASD-like behaviors over a 15-year period. One of three refractive surgery methods was employed, with the choice of method uniquely tailored to the child's eye anatomy. Laser photorefractive keratectomy (PRK) was performed in 131 children, implantation of a phakic intraocular lens (pIOL) in 115 children, and removal of the crystalline lens and implantation of an intraocular lens (refractive lens exchange, RLE) in 21 children. All procedures were performed under brief general anesthesia, with the child returning home on the same day. The median age at surgery was 10.9 years and the median follow-up period was 3.1 years. Pre-operative refractive errors ranged from a mean (standard deviation) +7.5 (0.09) D to -14.3 (4.8) D. Surgery corrected 87% of the children to normal focal length (± 1 D). Visual acuity improved an average of 0.6 logarithm of the minimum angle of resolution, the equivalent of 6 lines on a standard eye chart. Change in visual acuity was significant (all P < 0.01) between baseline and the most recent follow-up examination in each of subgroups. Change in spherical equivalent refractive error at 3, 12, 24, 36, 60, and > 60 months post-operatively were significant (all P < 0.01) between baseline and each follow-up visit in each of subgroups. Social interactions and ASD behaviors improved in 72% (192) of the treated children (P < 0.01). The incidence of sight-threatening complications was low. Refractive surgery improves both visual function and behavior in most children with ASD and major myopia, hyperopia, or astigmatism. The PRK, pIOL, and RLE procedures appear to be effective and reasonably safe methods for improving refractive error, visual acuity, and behavior in many ametropic children with ASD and ASD-like NDDs.

Superior optical limiting performance of lead-free metal halide perovskites nano-crystals embedded chalcogenide glass

The nonlinear optical properties of metal halide perovskites (MHP) are highly attractive, making them an emerging hotspot in the field of perovskite photonics. In this study, the third-order optical nonlinear properties of lead-free MHP (CsSnCl3) nano-crystals (NCs) embedded in a chalcogenide glass (GeS2-Sb2S3) substrate were characterized using the Z-scan technique. The spectral range examined was from 750 to 900 nm. Experimental results revealed that the incorporation of CsSnCl3 NCs enhanced the nonlinear refraction and nonlinear absorption behavior of the GeS2-Sb2S3 glass. Furthermore, the magnitude of these effects increased with the growth size of the CsSnCl3 NCs. Importantly, the MHP glasses exhibited strong two-photon absorption due to the large multiple-absorption cross-section of MHP crystals and the intrinsic high optical nonlinearity of the chalcogenide glass. The superior optical limiting performance induced by this process was successfully demonstrated.

Tunable dynamic metamaterial for negative refraction

The effective ability to manipulate the negative refraction behaviors of electromagnetic waves in the terahertz (THz) frequency range is of great interest for various practical applications in communication, imaging, and sensing. In this study, we propose a robust graphene-integrated metamaterial design for the dynamic manipulation of negative refraction at terahertz frequencies. Using the distinctive characteristics of graphene combined with the specially designed metamaterial structure, we demonstrated the active control of negative refraction by modulating the graphene's chemical potential from 0.0 to 1.0 eV. By dynamically tuning the carrier density of graphene, we create the switchable states of the negative index for the transmission or the reflection modes, tailoring the terahertz wave behavior in real time. In particular, in the case of different applied temperatures (through the bias applied voltages) of the proposed metamaterial, these two modes are maintained over 60% for both reflection and transmission while preserving the negative refractive index. Our results reveal the tunability of negative refraction, paving the way for developing reconfigurable THz meta-devices with enhanced functionalities in the near future.

A simple new method for retrieving spectral changes of the refractive index of thin films from transmission spectra

A new method for calculating the refractive index spectral behaviour of thin films is presented. The method is based on introducing the idea of the order of appearance technique to accurately find the order of interference and Cauchy fitting parameters of the interference peaks observed in the transmission spectra of the thin film under investigation. A very simple mathematical relationship was found that relates the order of appearance and wavenumber of the interference peaks observed in the transmission spectrum. Fitting the data extracted from the measured transmission spectra to the newly found simple mathematical relation, we can extract the order of interference and Cauchy fitting parameters of the thin film under investigation. In addition, the thickness of the film was extracted and found to agree well with the thickness measured using the spectroscopic ellipsometery technique. The proposed method of calculation was successfully applied to five binary semiconductor samples, which are ZnO, ZnTe, ZnS, ZnSe, and SiO2. A very good agreement was found between the proposed method of calculation and the well-known method presented by Swanepoel. Finally, the effect of surface roughness on the FECO peak wavelength was discussed.

Observation of triple-branch valley topological edge states and abnormal refraction in elastic phononic crystal plates

Topological edge states (TES) have attracted wide interest in elastic waves, due to its backscattering immunity and directional wave transportation. In this work, the triple-branch TES and their rich refraction behaviors are investigated in one single valley chiral phononic crystal (PC) plate with double-sided symmetric pillars. The triple-branch TES emerge simultaneously in one structure, and their robust transportation against disorder, cavity, and sharp bends are demonstrated in both simulation and experiment. Furthermore, the refraction behaviors for triple-branch TES from PC plate into bare plate are unveiled both theoretically and experimentally, leading to the normal refraction for first branch TES while the abnormal refraction for the second or third branch TES. These results offer opportunity for designing mechanical device or controlling the wave propagation along phonon circuits in multiple bandwidths and with robustness.

High transparency of PbO–BaO–Fe2O3–SrO–B2O3 glasses with improved radiation shielding properties

This study investigated the role of PbO and BaO on the optical and radiation shielding properties of PbO–Fe2O3–SrO–B2O3–BaO glass systems. Optical studies indicate that the prepared glass samples are transparent within the visible spectrum; the transparency increases marginally with increasing PbO/BaO concentrations. Furthermore, by increasing the PbO/BaO ratio, the BO4 units increase (BO3 units decrease), and the density values increase. In addition, the optical band gaps widen, and linear and nonlinear refractive indices decrease. The reductions in nonbridging oxygen were responsible for the increased band gaps and decreased refractive index behavior. Moreover, the ionizing radiation shielding studies showed improved behavior with additional PbO additives. Also, the HVL values of the present glass samples are comparatively lower than the HVL of some standard ionizing radiation shielding materials. Finally, the combination of effective radiation shielding properties and high transparency makes the current glass samples good candidates in the ionizing radiation shielding field.

The refractive behaviour of the human eye under different ambient lighting conditions

Background: Adjustment of the ocular accommodative system is an important phenomenon allowing for optimal vision at different distances.Aim: The study compared the refractive behaviour of the human eye under different ambient lighting conditions for different target brightness.Setting: Auto-refraction measurements were taken of the participants in the Department of Optometry at the University of Johannesburg.Methods: Five African participants from a single ethnic group aged between 20 years and 25 years, had 40 successive auto-refractor (Nidek AR 610) measurements taken on the right eye of each participant in a bright and dark room using the illuminated and dark targets (LL and DL); dark target in the illuminated and dark room (LD and DD).Results: A change in the refractive state of all participants was observed on LL and LD, except for one, who experienced myopic shifts. The largest significant difference in the variance-covariances and the means was approximately 2.40 dioptre (D). The other participants’ shifts in means were approximately the same and varied between 1.00 D and 1.50 D stigmatic shift. For the DL to DD conditions all participants, except for one, underwent a hyperopic shift of about 0.50 D.Conclusion: The refractive behaviour of the human eye appears to be dependent on ambient light conditions as well as target illumination or luminance.Contribution: The study is scientific and clinical, and focuses on changes in refractive behaviour under different lighting conditions, falling within the scope of the journal. Key insights are that there is a change in the refractive behaviour of the eye under different ambient conditions.

Correlating the Density and Refractive Index of Ternary Liquid Mixtures

Some physical properties of ideal solutions, e.g. the molar volume and the molar refraction, vary linearly with composition. Others can be expressed, either as ratios or as products of two other properties which vary with composition in this way. It is postulated that the non-ideal behaviour of real solutions can be adequately modelled by substituting these linear functions with higher order Scheffé polynomials. A suite of such models is presented for which the parameters are fully determined by knowledge of pure component properties and binary behaviour. Their binary data representation ability, and capacity to predict ternary properties, was tested using density and refractive index data for the acetic acid–ethanol-water ternary system as well as fourteen additional ternary data sets. Model performance was ranked on the basis of the Akaike Information criterion. With respect to predicting ternary density and refractive index behaviour from knowledge of binary data, it was found that lower-order models outperformed higher order models.

Highly stable femtosecond pulse generation enabled by the indium tin oxide nanocrystals

The ultrafast third-order optical nonlinearity of indium tin oxide nanocrystals (ITO NCs) and their application in femtosecond laser generation have been investigated experimentally. The ITO NCs exhibit a large modulation depth of ∼25%, nonlinear refractive behavior with self-focusing, ultrafast carrier recovery time of ∼300 fs, and high damage threshold of ∼1.16 TW cm−2, and the stable femtosecond Er-doped fiber laser can be delivered with a signal-to-noise ratio over 80 dB modulated by the ITO NCs successfully. The experimental results indicate that the ITO NCs can be excellent ultrafast nonlinear optical materials for developing highly stable photonic and optoelectronic devices.

High-accuracy calibration method for an underwater one-mirror galvanometric laser scanner.

Three-dimensional (3D) perception of deep-sea targets is the key to autonomous operation of underwater equipment (e.g., underwater robots). Underwater one-mirror galvanometric line-laser scanner has advantages for short-range measurement, but it is difficult to achieve high calibration accuracy due to installation errors and refraction effects. For this reason, in this paper, a high-accuracy refraction-considered and installation-error-independent calibration method is proposed for the vision system. Firstly, to address the difficulty of aligning the incident light plane with the galvanometer shaft, a high-accuracy land-based installation-error-independent model is proposed, which avoids the influence of the installation errors and allows the real shaft axis and the light-plane cluster poses to be calculated using only three light planes. Subsequently, considering the underwater refraction, a 3D model is established for simulating refractive behaviors of the light-plane cluster, and then a partition-based method is proposed for calibrating the underwater light-plane cluster, which further improves the calibration accuracy of the scanner in underwater measurement scenarios. Finally, a one-mirror galvanometric laser scanner is developed in the laboratory to verify the calibration accuracy and to perform the 3D measurement experiments of underwater targets. The results show that the calibration accuracy of the proposed land-based installation-error-independent model is improved 2 times more compared with the traditional installation-error-dependent model. Additionally, the measurement accuracy of the scanner for the standard sphere is 11.98 µm and 12.75 µm in the air and underwater measurement scenarios, and the two measurements are in good agreement. The above results comprehensively verify the high accuracy of the calibration method proposed in this paper.

Wideband 5G Antenna Gain Enhancement Using a Compact Single-Layer Millimeter Wave Metamaterial Lens

This paper presents a very compact, wideband, and enhanced-gain antenna for 5G applications. A simple single-layer millimeter wave (mm-wave) metamaterial lens (meta-lens) is used to improve the gain, aperture efficiency, and gain bandwidth of a slotted-patch antenna over a wide range of frequencies from 25 GHz to 31 GHz. The lens exhibits a metamaterial negative refractive index behavior, which is attributed to a substantial gain enhancement of around 4-5 dBi over the whole band compared to the gain values of the slotted patch antenna alone. The lens’s unit cell comprises a simple single-layer split ring resonator (SRR) whose dimensions are carefully chosen to improve transmitted power and suppress absorbed and reflected power. The meta-lens consists of 8×8 subwavelength SRR unit cells. Each cell has an area of 1.6×1.6 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , it is located in the near-field region closely above a slotted patch antenna to produce a total antenna size of 12.8 ×12.8 ×7.27mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> ( 1.2 λ × 1.2 λ × 0.68 λ, where λ is the free space wavelength at 28 GHz). The maximum gain of the proposed antenna is 12.7 dBi, the 1 dB gain bandwidth is 18%, the maximum aperture efficiency is 92%, and the -10 dB impedance bandwidth (10 dB B.W.) is 17%. This excellent combination of essential metrics is hard to realize at mm-wave using narrowband antenna structures (microstrip patch antennas), and the aperture efficiency is the highest thus far for such a class of antennas.