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A flat telescope (FTS), which incorporates an all-dielectric metasurface doublet (MD) based on hydrogenated amorphous silicon nanoposts, is proposed and demonstrated to achieve flexibly magnified angular beam steering that is sensitive to both light polarization and deflection direction. Specifically, for transverse-electric-polarized incident beams, the MD exhibits deflection magnification factors of +5 and +2, while for transverse magnetic polarization, the beam is steered in reverse to yield magnification factors of −5 and −2 in the horizontal and vertical directions, respectively. The proposed MD comprises cascaded metalenses, which can invoke polarization-selective transmission phases. The MD which emulates a set of convex and concave lenses renders positively increased beam deflection, whereas the case corresponding to a pair of convex lenses facilitates negatively amplified beam deflection. The essential phase profiles required for embodying the MD are efficiently extracted from its geometric lens counterpart. Furthermore, the implemented FTS, operating in the vicinity of a 1550 nm wavelength, can successfully enable enhanced beam steering by facilitating polarization-sensitive bidirectional deflection amplifications. The proposed FTS can be applied in the development of a miniaturized light detection and ranging system, where the beam scanning range can be effectively expanded in two dimensions.

The conventional nanoscale anti-counterfeiting scheme, exhibiting limited encoding capacity, faces growing challenges of being falsified with the advent of advanced high-resolution equipment. In this study, we propose a multilevel anti-counterfeiting device based on a femtosecond laser (fs-laser) treated plasmonic gold nanocluster/graphene (AuNC/Gr) hybrid structure integrated with a resonant cavity. The covert structural features encoded in random colored patterns, optical reflection spectra, and Raman spectra constitute three classes of anti-counterfeiting signatures, which originate from the AuNC-covered Gr, which initiates plasmonic and thermal couplings. The attendant inverted thermal distribution is presumed to confine the structural features to the AuNC-Gr interface while leaving no detectable traces on the surface of AuNC/Gr even under advanced high-resolution equipment. Therefore, the proposed approach achieves multilevel anti-counterfeiting accomplishing physically unclonable functions in the form of random colored patterns, reflection spectra, and Raman spectra. As the first report for realizing remarkable optical modulation (i.e., random colored patterns) without any surface trace or damage via fs-laser-AuNC/Gr interaction, our study also discloses the outstanding performance of Gr in fs-laser-induced optothermoplasmonic lithography on near-percolation metal films. Simultaneously, the demonstrated fs-laser-processed plasmonic hybrid structure in conjunction with a resonant cavity is anticipated to expand the encoding capabilities for nanoscale anti-counterfeiting while avoiding the risk of being imitated because of the covert structural features.

We propose and design a flat optical phased array (OPA) receiver that consists of a grating antenna, a free-propagation region (FPR) incorporating an on-chip metalens concentrator (OCMC), and an output port of a tapered waveguide. By concatenating the OCMC-integrated FPR with the antenna, the proposed OPA allows light coupled at a slanted ψ angle to be conveyed to the output, thereby resolving the challenges of phase-controlled light detection. To impose a space-dependent phase on the incident light from the antenna, the OCMC is constructed by laterally arranging subwavelength slot meta-atoms with varying slot lengths, which are created in the core layer of a slab and uniformly quantized at 16 phase levels. Hence, without the aid of phase modulators, the light beam emerging from the grating antenna can be focused on the output port through angle-tolerant coupling along the lateral direction. The miniaturized OCMC was confirmed to play a pivotal role in achieving enhanced in-plane coupling efficiency over the field of view.

Compact optical sensors are deemed to be of significant importance in industrial applications owing to their high performance and cost-effectiveness. In this study, a linearity-enhanced refractometric sensor was developed by employing an ultra-high numerical aperture (UHNA) fiber tethered to a plastic prism. The proposed refractometer can appropriately alter the intensity profile of incident light over the sensing area associated with the prism by adopting UHNA fibers with different mode profiles as the lead-in fiber. This provides an adjustable sensing regime that yields a linear response with a coefficient of determination (R 2 ) over 0.99. The fabricated sensor achieved a sensitivity of 13.6 per refractive index unit (RIU) and a high resolution of 5.80 × 10 -5 RIU for refractive indices ranging from 1.3166 to 1.3826 at λ = 1550 nm. Further, the proposed sensor was successfully applied to inspect the refractive index of a sample of coolant used in metalworking equipment, indicating that the proposed refractometric sensor can facilitate real-time monitoring of industrial production processes.

This study proposes a miniaturized refractometer with adjustable sensitivity that incorporates a reflective prism linked to a pair of precision-aligned fibers. An incident beam emanating from a single-mode fiber (SMF) undergoes Fresnel reflection at the interface between a slanted sensing facet of the prism and the aqueous solution under test and is properly steered via an aspheric mirror facet of the prism toward a multi-mode fiber (MMF). The refractive index (RI) of the solution can be accurately measured by observing the optical power. The sensitivity and sensing range with respect to the RI may be flexibly adjusted by tailoring the wedge angle of the prism. The proposed refractometer has been designed through rigorous simulations then constructed by integrating an appropriate prism in polycarbonate to both an SMF and MMF imbedded in a silicon chip. The embodied refractometric sensor was practically applied to inspect an aqueous sucrose solution, whose RI was varied from 1.3166 to 1.4029 for λ = 1550 nm. As for the major achieved performance, the sensitivity ranged up to 54.6 per refractive index unit (RIU) while the resolution was as small as $9.95\times 10^{\hbox{--} 6}$ RIU. The sucrose solution could be efficiently in situ monitored to provide a minimum detectable RI change of ∼0.0001.

A photothermally tunable diffraction grating incorporating two grating patterns was inscribed by femtosecond laser on photothermal actuator composed of graphene oxide and polydimethylsiloxane layers. Tailoring light stimulus can induce different diffraction patterns in contactless way.

A flat retroreflector based on metasurface doublet is proposed and created via lithographical nanofabrication. A high-speed wireless optical communication system with wide-angle tolerance is demonstrated at a telecommunications wavelength of λ = 1550 nm.

Bifunctional beam manipulation, including vortex generation and beam collimation, is achieved by tailoring the phase profiles encoded in the fiber meta-tip (FMT). A pair of FMTs are combined to establish an efficient polarization-selective optical interconnect.

We demonstrated a free space 1R regenerator incorporating an optical phased array based on a bidirectional grating antenna, enabling transmission and reception of optical signals at up to 10 Gbps.

We propose and demonstrate an optical phased-array-based bidirectional grating antenna (BDGA) in silicon nitride waveguides. The BDGA is integrated with a miniaturized all-dielectric metasurface doublet (MD) formed on a glass substrate. The BDGA device, which takes advantage of alternately feeding light to its ports in opposite directions, is presumed to effectively provide a doubled wavelength-tuned steering efficiency compared to its unidirectional counterpart. The MD, which is based on vertically cascaded convex and concave metalenses comprising circular hydrogenated amorphous silicon nanopillars, is meticulously placed atop the BDGA chip to accept and deflect a beam emanating from the emission area, thereby boosting the beam-steering performance. The manufactured BDGA could achieve an enhanced beam-steering efficiency of 0.148 deg/nm as well as a stable spectral emission response in the wavelength range of 1530–1600 nm. By deploying a fabricated MD atop the silicon photonic BDGA chip, the steering efficiency was confirmed to be boosted by a factor of ∼ 3.1 , reaching 0.461 deg/nm, as intended.

A highly sensitive electro-optic (EO) probe has been proposed and realized by tethering an ultra-high-quality (

A light-driven diffraction grating incorporating two grating patterns with different pitches atop a photothermal actuator (PTA) has been proposed. It is based on graphene oxide/reduced graphene oxide (GO/rGO) induced via femtosecond laser direct writing (FsLDW). The rGO, its controllable linewidth, and transmission support the formation of grating patterns; its noticeably small coefficient of thermal expansion (CTE), good flexibility, and thermal conductivity enable the fabrication of a PTA consisting of a polydimethylsiloxane layer with a relatively large CTE. Under different intensities of light stimuli, diffraction patterns can be efficiently tailored according to different gratings, which are selectively addressed by incident light beam hinging on the bending of the PTA. This is the first demonstration of combining gratings and PTA, wherein the GO plays the role of a bridge. The light-driven mechanism enables the contactless operation of the proposed device, which can be efficiently induced via FsLDW. The diffraction angle could be changed between 2° and 6° horizontally, and the deviation of side lobes from the main lobe could be altered vertically in a continuous range. The proposed device may provide powerful support for activating dynamic diffraction devices in photothermally contactless schemes.

A highly sensitive electro-optic (EO) probe has been proposed and realized by tethering an ultra-high-quality (Q)-factor LiNbO3 etalon to a single-mode fiber operating at around a 1550-nm wavelength. For the adopted EO etalon, the electric-field-induced refractive index modification is deemed to shift its own spectral response. An electrical modulation signal is anticipated to be produced when a probe light beam with a fixed bias wavelength impinges upon the EO etalon. The EO etalon is particularly required to exhibit a remarkably steep spectral response and thus facilitate modulation efficiency. In aiming to scrutinize the performance in terms of sensitivity, two EO probes involving profoundly different Q-factors were prepared and applied to detect the electric field emitted from a microstrip device. It was confirmed that the sensitivity could be efficiently enhanced by as much as 28 dB by boosting the Q-factor 18 times when a probe light beam operating at =∼1550 nm was properly collimated and polarized. Accordingly, the minimum detectable signal was successfully diminished.