Sang-Shin Lee

Kwangwoon University · Department of Electronic Engineering

The growing demand for enhanced data transmission and network scalability requires connecting multi‐mode fibers (MMFs) to single‐mode fibers (SMFs). However, conventional fiber‐optic connector systems face challenges such as one‐way transmission, alignment issues, and bulkiness. In this study, an all‐dielectric metasurface (MS)‐based fiber‐coupling...

We propose and demonstrate an integrated optical switch that leverages an optical phased array (OPA) and an on-chip metalens, highlighting its potential for efficient and scalable beam switching across multiple ports within a compact footprint. The device consists of an input multimode interference (MMI) coupler, a phase modulator (PM) array, a bea...

We propose and demonstrate an angularly offset multiline (AOML) dispersive silicon nitride optical phased array (OPA) that enables efficient line beam scanning with an expanded field of view (FOV) and plateau envelope. The suggested AOML OPA incorporates multiline OPA units, which were seamlessly integrated with a 45° angular offset through a therm...

Virtual reality devices featuring diffractive grating components have emerged as hotspots in the field of near-to-eye displays. The core aim of our work is to streamline the intricacies involved in devising the highly efficient slanted waveguide grating using the deep-learning-driven inverse design technique. We propose and establish a tandem neura...

This study proposes a solid-state two-dimensional beam-steering device based on an electro-optical phased array (EOPA) in thin-film lithium niobate (TFLN) and silicon nitride (SiN) hybrid platforms, thereby eliminating the requirement for the direct etching of TFLN. Electro-optic (EO) phase modulator array comprises cascaded multimode interference...

Efficient and rapid beamforming methods are essential for calibrating phase errors in optical phased array (OPA) technology, particularly for LiDAR applications. Maintaining a stable beamformed state amidst environmental fluctuations poses a significant challenge, requiring frequent recalibration whenever the state is disrupted. To address this, we...

As a promising technology, refractive index (RI) sensing has been developed for biosensing and chemosensing applications as well as for multiple industrial applications. Nevertheless, conventional RI sensors are confined by their operating principle or detection devices in terms of high sensitivity or a wide detection range. This study experimental...

The measured coupling efficiency between the SiN SWG edge coupler and SMF-28 was scrutinized. • It is anticipated that the SWG structure has not been fabricated as designed due to fabrication errors, so the effective refractive index is different from the calculated value. • After identifying the cause through FIB analysis, the SiN SWG edge coupler...

Optical trapping is a state-of-the-art methodology that plays an integral role in manipulating and investigating microscopic objects but faces formidable challenges in multiparticle trapping, flexible manipulation, and high-integration applications. In this study, we propose and demonstrate a switchable optical scheme for trapping microparticles in...

Developing an optical geometric lens system in a conventional way involves substantial effort from designers to devise and assess the lens specifications. An expeditious and effortless acquisition of lens parameters satisfying the desired lens performance requirements can ease the workload by avoiding complex lens design process. In this study, we...

The remarkable capability in regulating light polarization or amplitude at the nanoscale makes metasurface a leading candidate in high-resolution image display and optical encryption. Diverse binary or grayscale meta-images were previously shown concealed in a single metasurface, yet they are mostly stored at same encryption level and share an iden...

The proposed SiN SWG edge coupler which has a length of 180 µm can achieve a high coupling efficiency of-1.06 dB with SMF-28. • And the 1-dB alignment tolerances are higher than ±2 and ±3 µm in horizontal and vertical directions, respectively. • The performance of the proposed design was verified through 3D FDTD simulation and experimental verifica...

Optical phased array (OPA) beam scanners for light detection and ranging (LiDAR) are proposed by integrating polymer waveguides with superior thermo-optic effect and silicon nitride (SiN) waveguides exhibiting strong modal confinement along with high optical power capacity. A low connection loss of only 0.15 dB between the polymer and SiN waveguide...

Conventional OPAs incorporating a diffraction grating were mainly developed to achieve a two-dimensional spot beam-based scan, which inevitably requires a wide range of wavelength tuning, leading to unaffordable complexity and limited scanning speed. In this study, we demonstrate a hybrid OPA that capitalizes on a silicon nitride line beam emitter...

Fiber-optic refractive index (RI) sensors based on wavelength-shift-based interrogation continue to present a challenge in achieving high sensitivity for a wide detection range. In this paper, we propose a sensor for determining the RI of liquids based on femtosecond laser (fs-laser) writing of a dual-side polished singlemode–multimode–singlemode (...

Three-dimensional (3D) graphene (Gr) has been successfully grown on a patterned sapphire substrate (PSS) with very low mismatch between Gr and the sapphire nanostructure through metal-catalyst-assisted chemical vapor deposition (CVD). However, the transfer of the 3D Gr film without compromising the structural integrity of Gr is challenging because...

We have proposed a metalens-integrated optical phased array, enabling on-chip based optical manipulating with wavelength tuning. The movement of the focal point is demonstrated while there are no moving parts.

The currently used liquid identification techniques are costly, cumbersome, and spectrometer-reliant. In this study, a compact, accurate, and cost-effective method for identifying liquids was presented using visual intelligence algorithms and a metasurface-incorporated optofluidic device incorporated.

An ultra-fast and novel phase calibration method for an optical phased array has been developed using the MODE API on Python. With an adaptive moment estimation (Adam) algorithm, the optimal phase set is obtained by finding the maximum light intensity in the target direction.

As optical phased arrays (OPAs), used as solid-state beam scanning elements, swiftly stride towards higher efficiency and faster scanning speed, the line beam scanner is emerging as a viable substitute for its counterpart relying on point-beam-incorporated raster scanning. However, line-beam scanners require active phase shifters for beam scanning;...

We propose high-speed electro-optic modulator based on a thin-film LiNbO3-Si3N4. When the electrode length is 11.5 and 16.5 mm and the electrode gap is 7 and 6 μm, respectively, the halfwave voltage-length product, Vπ·L is 2.94 and 2.66 V·cm, respectively. It is expected that high speed and low power consumption will be realized by further improvin...

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...

The stability of methylammonium (MA)-based perovskite solar cells (PSCs) remains one of the most urgent issues that need to be addressed. Inherent weak binding forces between MAs and halides cause the perovskite structure to become unstable under exposure to various external environmental factors such as moisture, oxygen, ultraviolet radiation, and...

A phase calculation scheme, which gives required phase profiles extracted from pre-designed geometric lenses, was proposed and demonstrated for designing highly customizable metalens-based devices expanding the related research and practical applications.

We propose high-speed electro-optic modulator based on a thin-film LiNbO 3-Si 3 N 4. When the electrode length is 11.5 and 16.5 mm and the electrode gap is 7 and 6 μm, respectively, the halfwave voltage-length product, V π •L is 2.94 and 2.66 V·cm, respectively. It is expected that high speed and low power consumption will be realized by further im...

A phase calibration method for an optical phased array was developed using LabVIEW graphical programming environment. With genetic algorithm, the optimal phase set is obtained by finding the maximum of the light intensity of the main lobe.

A hybrid edge and grating coupler allowing full-scale wafer and chip-level testing is demonstrated, which achieves insertion loss below 1.2 dB and extinction ratio above 17 dB while operating with either of the couplers.

In silicon photonics, grating-assisted fiber-to-waveguide couplers provide out-of-plane coupling to facilitate wafer-level testing; however, their limited bandwidth and efficiency restrict their use in broadband applications. Alternatively, end-fire couplers overcome these constraints but require a dicing process prior usage, which makes them unsui...

Trifunctional Manipulation of Light In article number 2100603, Yang Li, Wenjing Yue, Duk‐Yong Choi, and colleagues demonstrate a facile method for realizing efficient and trifunctional manipulations of full‐space visible light based on a type of dielectric metasurface doublet incorporating cascaded polarization‐filtering meta‐atoms. Through the sel...

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 t...

Multilayered plasmonic metasurfaces have been previously shown to enable multifunctional control of full‐space electromagnetic waves, which are of great importance to the development of compact optical systems. While this structural configuration is practical for acquiring metasurfaces working in microwave frequency, it will inevitably become lossy...

The phase error imposed in optical phased arrays (OPAs) for beam scanning LiDAR is unavoidable due to minute dimensional fluctuations that occur during the waveguide manufacturing process. To compensate for the phase error, in this study, a fast-running beamforming algorithm is developed based on the rotating element vector method. The proposed alg...

We demonstrate a metasurface doublet-integrated bidirectional grating antenna to mitigate the limitation of the beam steering range of the optical phased array. We show that a wavelength-controlled beam steering efficiency is improved by 0.888 deg/nm.

A gold/graphene hybrid layer works as triple-level anti-counterfeiting after femtosecond laser irradiation. The presence of graphene enables key structural information related to anti-counterfeiting signatures to be covert thoroughly under the surface of the hybrid layer.

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 presu...

In this article, Duk-Yong Choi, Sang-Shin Lee, and co-workers demonstrate a flat retroreflector (FRR) based on metasurface doublet in the telecommunications wavelengths. The proposed FRR was utilized to achieve a reliable and angle-tolerant optical link bridging the gap between metasurface-based devices and future integrated communication systems.

A compact silicon nitride polarization beam splitter with a length of 57-μm achieving high extinction ratio is presented. It also incorporates phase change material, which allows us to switch it on and off.

Facilitated by the ability to reflect radiation along its incident direction, retroreflectors have been perceived as a pivotal component for establishing reliable free‐space optical links. However, conventional retroreflectors suffer from limited integration because of their bulky size, heavy weight, and nonplanar shape. Metasurface‐based devices c...

We propose a compact silicon nitride edge-coupler with a footprint of 76 µm using cascaded taper segments. It exhibits a coupling efficiency above 90% for C and L bands and excellent alignment and cleaving tolerances.

In article number 2000581, Sang‐Shin Lee and co‐workers demonstrate a fiber meta‐tip constructed by tethering an all‐dielectric metasurface to a single‐mode fiber for bifunctional light manipulation, including vortex generation and beam collimation. Furthermore, the feasibility of employing the established fiber meta‐tips for applications such as o...

“Lab‐on‐fiber” technology, which combines the unique merits of optical fibers with nanophotonic platforms, has received significant investigation due to its profound ability to control light at the nanoscale, which has significantly boosted the functionalities of conventional fibers. Previous plasmonic‐based fiber meta‐tips (FMTs) have been inhibit...

Silicon nitride (SiN) optical phased arrays (OPAs) have emerged as a potential alternative to their silicon counterparts, owing to their low nonlinearity, easy scalability, and low propagation loss. However, the development of SiN OPAs for light detection and ranging (LiDAR) applications has attracted less attention due to the low thermooptic (TO)...

Optical metasurface has exhibited unprecedented capabilities in the regulation of light properties at a subwavelength scale. In particular, a multifunctional polarization metasurface making use of light polarization to integrate distinct functionalities on a single platform can be greatly helpful in the miniaturization of photonic systems and has b...

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.

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 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...

We have proposed and experimentally realized an ultra-compact and broadband silicon nitride edge-coupler that enables high coupling efficiency. The proposed coupler was realized by concatenating short tapers in four stages, whose angles were designed to minimize the footprint while preserving the coupling efficiency. The constituting taper segments...

A gain-clamped SOA has been designed and demonstrated using two passive waveguides with Bragg grating reflector in a silicon nitride platform at λ=1.55 µm. We experimentally obtained the gain, saturation output power, and noise figure equivalent to 20.69 dB, 8.54 dBm, and 15.51 dB, respectively.

A virtual‐moving metalens array (VMMA) enabling light‐field imaging with enhanced resolution has been proposed and developed by Sang‐Shin Lee and co‐workers (see article number 2000820). The VMMA is based on a multifunctional dielectric metasurface, playing the role of imposing polarization‐sensitive phase profiles for orthogonal linear polarizatio...

The implementation of a polarization beam splitter (PBS) on a silicon nitride platform remains challenging owing to its relatively low index. We therefore propose a silicon nitride PBS that exploits serially cascaded asymmetric directional couplers (ADCs), leading to a high polarization extinction ratio (PER) over a broad bandwidth. The ADC spatial...

We developed a flexible perfect absorber based on a thin-film nano-resonator, which consists of metal–dielectric–metal integrated with a dielectric overlay. The proposed perfect absorber exhibits a high quality (Q-)factor of ~ 33 with a narrow bandwidth of ~ 20 nm in the visible band. The resonance condition hinging on the adoption of a dielectric...

The light‐field (LF) imaging technique can obtain the light intensity and directional ray distribution information by utilizing a microlens array (MLA). Based on the recoded 3D information, full‐parallax or depth‐slice images can be reconstructed. Due to the limited ray sampling rate of the MLA, however, conventional LF imaging schemes are fatally...

Silicon nitride (SiN) optical phased arrays (OPAs) have emerged as a potential alternative to their silicon counterparts, due to their potential use in enhanced solid-state light detection and ranging. Grating antennas based on a SiN waveguide suffer from a limited beam steering efficiency, owing to the relatively lower effective refractive index o...

In article number 2000645, Duk‐Yong Choi, Sang‐Shin Lee, and co‐workers demonstrate an all‐dielectric metasurface doublet providing multifunctional beam manipulation in the near‐infrared regime, including increased beam deflection, beam reduction, and polarizing beam splitting. The proposed metasurface is anticipated to incorporate a set of bulk op...

Multifunctional metasurfaces, which are planar devices featuring diverse functionalities, have attracted tremendous attention as they enable highly dense integration and miniaturization of photonic devices. Previous approaches based on spatial/spectral multiplexing of meta‐atoms on single metasurfaces are supposed to be inevitably limited in their...

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 appropria...

Solid-state light detection and ranging, capable of performing beam scanning without using any mechanical moving parts, requires a phase-modulator array. Polymers facilitate the fabrication of efficient phase modulators with low drive power, owing to their high thermo-optic (TO) effect and low thermal conductivity. We designed and fabricated a poly...