Device Length Research Articles

On-chip 7 GHz acousto-optic modulators for visible wavelengths

A chip-integrated acousto-optic phase modulator tailored for visible wavelengths has been developed. Utilizing the lithium niobate on sapphire platform, the modulator employs a 7 GHz surface acoustic wave, which is excited by an interdigital transducer and aligned perpendicular to the waveguide. This design achieves efficient phase modulation of visible light within a compact device length of 200 micrometers and holds the advantages of easy fabrication and high stability due to its simple unsuspended structure. In this high-frequency acoustic regime, the acoustic wavelength becomes comparable to the optical wavelength, resulting in pronounced single-sideband modulation behaviors. This observation underscores the phase delay effects in the acousto-optic interactions, and enables new opportunities for developing functional visible photonic devices and their integration with atom- and ion-based quantum platforms.

Liquid flow mode transition and hysteresis under passive control

The liquid flow mode exerts a significant influence on the dynamics of droplet breaking, with consequential effects on factors like droplet size and monodispersity. In various applications, including but not limited to inkjet printing, microcapsule preparation, and cell encapsulation, diverse production methods are employed, but they typically rely on some form of droplet breakup or liquid jet breakup to ultimately generate droplets. During the process of droplet formation, smaller satellite droplets, which are considerably smaller than the main droplet, are inevitably generated. These smaller droplets can lead to wastage of raw materials and reduced production efficiency. Passive control methods, which involve modifications to the structure of the dropper, effectively suppress the formation of satellite droplets, and prove to be more practical and manageable in actual production scenarios when compared to active control methods. In contrast to the jetting mode, the dripping mode of droplet molding exhibits greater stability and size uniformity, thereby better meeting the requirements for particle uniformity in the preparation of traditional Chinese medicine. This paper specifically investigated the transition from the jetting mode to the dripping mode and explored the hysteresis of this transition under the influence of gravity utilizing a passive control method. By incorporating a drainage device within the dropper along with a Y-channel, a drainage system was established to achieve passive control. The effects of the length and diameter of the drainage device, as well as the mass fraction of the solution, on the conversion of flow modes were analyzed.

Plasmonic electro-optic modulators based on epsilon-near-zero materials: comparing the classical drift-diffusion and Schrödinger-Poisson coupling models

We present the design, modeling, and optimization of high-performance plasmonic electro-optic modulators based on indium tin oxide (ITO), leveraging voltage-gated carrier density modulation. The carrier density is modeled using the classical drift-diffusion (CDD) and nonlinear Schrödinger-Poisson coupling (SPC) methods, with the latter providing precise carrier distribution profiles, particularly in epsilon-near-zero (ENZ) media like ITO. By combining the nanoscale field confinement of surface plasmon polaritons with the ENZ effect, our modulators, integrated with silicon waveguides and optimized for operation at λ = 1550 nm, achieve a 3-dB bandwidth of 210 GHz, an insertion loss of 3 dB, and an extinction ratio of 5 dB for a device length of under 4 µm. These results highlight the critical trade-offs between high-speed modulator operation and low insertion loss vs. extinction ratio, underscoring the necessity of precise carrier distribution modeling for ENZ materials in optoelectronic devices.

One-way multiple beam splitter designed by quantum-like shortcut-to-adiabatic passage

Abstract In this work, we introduce a quantum-mechanical shortcut-to-adiabatic passage (STAP) into the design of multiple beam splitter. The device consists of one input and N output waveguide (WG) channels, which are connected via a mediator WG. After reducing such (N + 2)-WG structure into a controllable 3-WG counterpart by Morris-Shore transformation, we point out that the structure is available for all possible three-level STAP methods. By implementing one of them which does not require additional couplings, we can achieve the multiple beam splitting with arbitrary ratios among the N outputs. What is more, the device length is significantly shortened. Except for this, it is quite unique that the design exhibits a one-way energy transport. The underlying physics is presented. These features may have profound impacts on exploring quantum technologies for promoting advanced optical devices.

Parallel six-mode-selective converter based on photonic crystal fiber without holes in the cladding.

Mode-selective converters (MSCs) play an indispensable role in mode division multiplexing (MDM) systems, and the commonly used cascaded waveguide-based MSCs not only have a relatively large size but also increase the insertion loss and mode crosstalk during the conversion process. In this paper, a parallel six-mode-selective converter (6-MSC) is proposed to enhance the integration of the device, which consists of a photonic crystal fiber (PCF) and six step-index fibers (SIFs). Here, a PCF without any holes in the cladding is proposed. Based on this structure, the distance between the PCF core and the SIF core can be arbitrarily adjusted, which greatly improves the design freedom of multi-core optical fiber devices. Simulation results show that at a wavelength of 1.55 µm, the proposed 6-MSC can achieve parallel conversion from the fundamental mode in each SIF to the corresponding modes (L P01x, L P01y, L P11a x, L P11a y, L P11b x and L P11b y) in the PCF at a device length of 800 µm. The maximum coupling efficiency is 96.22% and the crosstalk is below 3.45%. Moreover, the coupling efficiencies of all six mode pairs exceed 80% within the wavelength range of 1.538∼1.560 µm, and the 3-dB coupling efficiency bandwidth covers the entire C-band. To the best of our knowledge, this is the first report of parallel conversion between six orthogonal fiber modes and fundamental modes based on PCF. The proposed 6-MSC holds promising prospects for future integrated high-capacity MDM systems.

Dual subwavelength-grating topology for building polarization beam splitters

Abstract A polarization beam splitter (PBS) is key for building polarization-diversity systems in optical communication networks. Here, we propose a compact and easy-to-fabricate PBS based on a dual subwavelength-grating (DSWG) structure positioned between two Si waveguides on a silicon-on-insulator platform. The coupling strengths of the transverse-electric (TE) and transverse-magnetic (TM) modes were selectively modified, with TE mode suppression and TM mode enhancement. By optimizing the duty cycles along transverse and longitudinal directions of the DSWG structure, the device length is reduced by approximately 40%, and the polarization extinction ratio (PER) of the TM mode is improved by ~5 dB at a wavelength of 1.55 μm, compared to a single subwavelength grating (SSWG) structure. Numerical simulations revealed high polarization extinction ratios (PERs) and low insertion losses (ILs) of 26.7 dB (0.1 dB) for TE mode and 23.2 dB (0.28 dB) for TM mode, with a compact footprint of 1.34 × 2.86 μm². Across a bandwidth of ~90 nm within the C-band (1.53–1.56 μm), the proposed PBS achieves a TM mode PER of ~20 dB, a TE mode PER greater than 25 dB, and ILs below 0.25 dB for both modes. This approach, utilizing biaxial anisotropic metamaterials, offers a flexible method for integrating PBSs into photonic integrated circuits using standard semiconductor fabrication processes.

"Nano-In-Nano" Schottky Diodes Fabricated by Combining Self-Aligned Nanogap Patterning with Bottom-Up ZnO Nanowire Growth.

Nanoscale semiconductors offer significant advantages over their bulk semiconductor equivalents for electronic devices as a result of the ability to geometrically tune electronic properties, the absence of internal grain boundaries, and the very low absolute number of defects that are present in such small volumes of material. However, these advantages can only be realized if reliable contacts can be made to the nanoscale semiconductor using a scalable, low-cost process. Although there are many low-cost "bottom-up" techniques for directly growing nanomaterials, the fabrication of contacts at the nanoscale usually requires expensive and slow techniques like e-beam lithography that are also hard to scale to a level of throughput that is required for commercialization. A scalable method of fabricating such devices is demonstrated in this work by combining two bottom-up fabrication techniques. ZnO nanowire Schottky diodes are produced with a device length of a few tens of nanometers and a performance significantly exceeding a ZnO thin film equivalent. The first technique is adhesion lithography that allows self-aligned coplanar electrodes of different materials to be patterned with a nanogap ∼10 to 50 nm length between the two. In this case, one electrode is gold, while the other is a bilayer of titanium on a thin film of ZnO, and it is this thin film that allows the second technique, hydrothermal growth, to be used to grow ZnO nanowires directly across the nanogap. The resulting "nano-in-nano" Schottky diodes have a high rectification ratio >104, a low turn-on voltage <0.3 V, and a minimal off-state current <10 pA. This process could be used to realize a variety of nano-in-nano electronic devices in the future, including short channel gate-all-around (GAA) transistors.

Incidence and Risk Factors for Orthopedic Device-Related Pressure Injuries: A Systematic Review and Meta-Analysis.

As orthopedic trauma increases, the resultant use of orthopedic devices and associated pressure injuries has increased. This study aims to systematically evaluate the incidence and risk factors for orthopedic device-related pressure injuries. A systematic review and meta-analysis was conducted by searching PubMed, Embase, Cochrane Library, Web of Science, ClNAHL, China National Knowledge Infrastructure, Wanfang Database, and Chinese BioMedical Literature Database from their inception until November 30, 2023. The population included adult orthopedic surgery patients aged 18 and older. Studies included case-control, cohort, or cross-sectional designs reporting risk factors, incidence, or predictors of orthopedic device-related pressure injuries published in Chinese or English. Exclusion criteria included unavailable full text, duplicate publications, reviews, animal studies, and conference abstracts. Two researchers independently screened the literature, extracted the data, and assessed the quality of the literature. A total of eight papers involving 3,783 patients were included. Meta-analysis showed that the incidence of orthopedic device-related pressure injuries was 12.0%. Significant risk factors included duration of device wear [OR 1.197, 95% Cl (1.025, 1.369), p =.016] and the length of stay [OR 1.144, 95% CI (1.096, 1.199), p <.001]. The duration of device wear and length of stay are key factors contributing to orthopedic device-related pressure injuries. Clinicians should actively monitor and manage these factors to reduce the risk of these injuries.

Design and optimization of a low-loss waveguide taper for a narrow-band O-band multiplexer

The fast deployment of high-performance data centers accelerates the development of O-band wavelength division multiplexing (WDM) and its devices. To minimize insertion loss in WDM devices, it is essential to maximize coupling efficiency between optical fibers and waveguides at micro- and nano-scale. In this paper, we propose a low-loss waveguide tapered coupler and its optimization around 1310 nm. The coupler has a vertically placed double-layer rib taper as an intermediate waveguide, and the inverted taper is in a tapered tandem structure. Rib tapers are introduced in the intermediate waveguide and the fiber is coupled to the rib tapers, which are adiabatically reduced in width along the direction of the coupler to vertically reduce the mode size. To minimize footprint, a cascaded inverted taper is introduced. The maximum taper angle per stage corresponding to the long adiabatic taper is first determined. Subsequently, the long tapers are replaced with new shorter tapers. Several parameters are optimized using frequency domain time division (FDTD), including the output waveguide and input surface dimension, the height ratio of rib tapers, the length of inverted tapers, the length of rib tapers, and the tapered profile of tandem structure. The optimization results show that the coupler has an insertion loss of only 0.06 dB at 1310 nm with a device length of 513.4 µm. The two-stage in-plane coupler operates in O-band narrow-band with low insertion loss, offering an efficient solution for coupling fiber to on-chip waveguides.

Broadband Thermo-Optic Photonic Switch for TE and TM Modes with Adiabatic Design

Optical power switches are essential components in fiber optic communication systems, requiring minimal losses, a broad operating wavelength range, and high tolerance to fabrication errors for optimal performance. Adiabatic optical power switches inherently meet these criteria and are well suited for manufacturing processes which support large-scale production at low costs. This paper presents the design and simulation of an adiabatic switch with a flat response in the whole 1525–1625 nm wavelength range (C band and L band) for both TE and TM polarizations. The switch is based on the thermo-optic effect induced by local variations in temperature. The impacts of the design parameters, such as the device length and dissipated heat, are analyzed. The simulation results indicate that the switch achieved high efficiency and low insertion losses, highlighting the potential of adiabatic switches for reliable and scalable integration into advanced optical circuits.

A Method of Applying Mixtures to Optimize Grounding during Installation of Vertical Composite Grounding Devices

The article considers the method of using mixtures to optimize the electrophysical parameters of grounding devices in conjunction with vertical composite grounding conductors. It has been found that fluctuations in soil resistivity caused by changes in weather and climatic conditions can lead to instability of the ground loop resistance. The study shown that without appropriate measures, the resistance of the loop as a result of seasonal changes in soil properties may exceed acceptable values. This is fraught with deviations in the resistance to current spreading of grounding devices beyond the limits of acceptable parameters. To compensate for these fluctuations, a method is proposed to reduce the seasonality factor. Reducing seasonality plays an important role in ensuring the safety of service personnel and farm animals by maintaining the resistance of the grounding device within the limits of regulatory values. The authors discuss methods for artificially reducing the resistance of the ground loop, including increasing its size and using deep ground electrodes. The results of vertical electrode probing of the soil at the sites of grounding conductors are presented, the effect of humidity on the resistivity of the soil is shown, the influence of soil layering and the presence of moisture-saturated soil layers is considered. A method is proposed that allows the mixture to be introduced together with a vertical composite grounding device, the design of the coupling, tip and auxiliary device, experimental studies of the proposed designs are carried out and the results of measuring the current spreading resistance of such a grounding device with both standard and proposed couplings are presented. A comparison was made with a grounding device without the use of mixtures. The measurement results demonstrate that with an increase in the length of the grounding device, its diameter and the volume of the injected mixture, the resistance decreases. It is shown that the proposed solution makes it possible to reduce seasonality by 1.64–2.1 times, depending on the couplings used, and to obtain a grounding conductor with an equivalent diameter dozens of times larger than the diameter of a composite grounding conductor. The authors propose the use of soil-replacing mixtures to reduce soil resistivity and ensure the stability of the grounding loop throughout the entire service life. The proposed method of applying mixtures without pre-drilling makes it possible to reduce the cost of constructing grounding devices.

Doped-δ-doped transferred electron device for sustained terahertz signal generation

Abstract The performance of a novel transferred electron device structure aimed at sustaining high-frequency signals in the terahertz (THz) range is investigated. The device uses a highly doped δ-layer to split the n-doped device into two distinct regions, forming a doped-δ-doped configuration. The first region generates high-speed electrons toward the δ-layer, while the second region utilizes negative differential resistance to modulate electron speeds and sustain oscillations. An ensemble self-consistent Monte Carlo model is employed to analyze electron dynamics and THz signal generation in this structure under a constant bias. The design demonstrates superior performance, achieving a fundamental operating frequency of 427 GHz in a 600 nm length InP device, nearly a 50% increase over conventional notch-doped design, while maintaining the current harmonic amplitude. This design achieves higher frequencies without reducing device length and increasing doping density, effectively addressing the trade-off of the Kroemer criterion. The study of the effects of varying doping densities and region lengths on device performance, highlighting the importance of optimizing these parameters to sustain current oscillations and efficiently generate THz signals. This design offers a promising solution for a compact and efficient THz source.

Compact, low-loss, and broadband 2 × 2 Si optical coupler designed by covariance matrix adaptation evolution strategy

Abstract We experimentally demonstrate compact, low-loss, and broadband 2 × 2 Si optical couplers on a Si photonic platform designed using the covariance matrix adaptation evolution strategy (CMA-ES). The measured minimum insertion losses (ILs) in the C-band were 0.071 dB, 0.016 dB, 0.016 dB, and 45%–55% optical bandwidth were 140 nm, 136 nm, and 139 nm for device lengths of 7.56 μm, 9.64 μm, and 12.32 μm, respectively. The ILs are smaller than ever reported in 2 × 2 optical couplers shorter than 10 μm, and the optical bandwidths are much larger than a conventional directional coupler. The results validate the effectiveness of the proposed CMA-ES-based design method, extending the scope of application of our design method to the design of passive devices on Si photonics platform.

(Invited) Low Energy Methods for Highly Selective Etching and Surface Treatment of Advanced Nanodevices

In the pursuit of higher performance semiconductors, device length scales continue to shrink down to nanometer dimensions with emerging chip designs increasingly dependent on 3D structures to maintain scaling. Memory manufacturers have already deployed 3D NAND devices with ongoing development for 3D DRAM devices. Advanced logic manufacturers have already deployed 3D FinFET devices and are beginning to deploy more complex GAA (Gate-All-Around) 3D devices as well. Building 3D structures has increased the need for more sophisticated selective etching. As these selective etches have become critical to the formation of the device, atomic precision material loss is required with low contrast materials. We review several materials systems where insufficient selectivity control in plasma-based radical etch necessitates innovative approaches such as atomic layer passivation, low energy metastable activated radicals and plasma-less low energy thermal chemical etching.Dummy polysilicon removal requires full removal of the polysilicon with minimal film loss to dielectric films such as silicon oxide and silicon nitride. While polysilicon can be removed by either wet etch or dry etch, each approach has certain limitations that narrow the overall process window. Wet etch chemistries such as TMAH (tetramethyl ammonium hydroxide) anisotropically etch polysilicon preferentially along crystalline planes which can result in silicon residues at the bottom corners of trenches. Highly isotropic dry etch radical chemistries minimize silicon residues but have greater tendency to damage the underlying epitaxial silicon layer due to either excessive film loss or halogen radical penetration through the encapsulating film. We show that the introduction of atomic layer passivation modifies the top monolayer of an oxide encapsulation layer and consequently widens the epi damage-free window.Selective mask removal requires full removal of the organic mask with high selectivity to exposed epitaxial silicon surfaces. While plasma-generated radicals have been effectively used for some time, it has become increasingly difficult for both advanced FinFET and GAA devices as the epi film loss requirements lower to a single atomic layer. We propose the tail energy distribution of reactive species formed in the plasma region is the driving factor for epitaxial film loss. To reduce these effects, we apply MARS (Metastable Activated Radical Source) technology where reactive species are indirectly formed outside the plasma region though collisions with metastable intermediates. The result is a significant reduction in higher energy species flux to the surface corresponding to a lower epi loss than conventional radical approaches.GAA device integration relies on depositing and subsequently removing SiGe layers to form Si-nanowires or nanosheets. Fluorine radical-based chemistries have limited selectivity to silicon because the bond strength difference between Si-Si and Si-Ge is exceedingly narrow and about 0.3 eV. We show a thermal chemical etching approach that achieves substantially higher SiGe:Si selectivity than radical etching on both blanket films and test structures. In addition, we highlight the strict film loss requirements that require highly selective native oxide removal prior to removing SiGe layers. We describe a thermal chemical etching approach that applies wet etch mechanisms in a vacuum environment to achieve high selectivity to both silicon and silicon nitride.

High-performance and scalable polarization splitter-rotator based on photonic crystal nanobeam reflection.

The polarization splitter-rotator (PSR) is a key device for polarization processing in polarization diversity systems, which has wide applications in achieving polarization independence and mixed multiplexing. However, it remains a significant challenge to simultaneously achieve a better balance in bandwidth, crosstalk (CT), polarization extinction ratio (PER), and compact footprint of the PSR. In this article, a photonic crystal nanobeam (PCN) structure is introduced to PSR for large bandwidth and compact size, with a device length of only 104 µm. Additionally, to achieve lower CT, a bridge waveguide is introduced for primary filtering. Simulation results show that the insertion loss (IL) is less than 0.55 dB, CT less than -35 dB, and PER greater than 35 dB within a bandwidth exceeding 110 nm, while maintaining a large process tolerance. Furthermore, the proposed PSR design breaks through the limitations of traditional schemes by extending its functionality effectively. To further improve integration, a novel approach to PSR using mode hybridization followed by spatial beam splitting is proposed. By controlling the phase-matching condition of various modes in different waveguides, the designed spatial beam splitting achieves lower CT and better compactness. Simulation results verify that the IL of the improved scheme is less than 1 dB, CT less than -24 dB, and PER greater than 22 dB within an 85 nm bandwidth, while reducing the overall length to less than 20 µm.

Graphene Phase Modulators Operating in the Transparency Regime.

Next-generation data networks need to support Tb/s rates. In-phase and quadrature (IQ) modulation combine phase and intensity information to increase the density of encoded data, reduce overall power consumption by minimizing the number of channels, and increase noise tolerance. To reduce errors when decoding the received signal, intersymbol interference must be minimized. This is achieved with pure phase modulation, where the phase of the optical signal is controlled without changing its intensity. Phase modulators are characterized by the voltage required to achieve a π phase shift, Vπ, the device length, L, and their product, VπL. To reduce power consumption, IQ modulators are needed with <1 V drive voltages and compact (sub-cm) dimensions, which translate in VπL < 1Vcm. Si and LiNbO3 (LN) IQ modulators do not currently meet these requirements because VπL > 1Vcm. Here, we report a double single-layer graphene (SLG) Mach-Zehnder modulator (MZM) with pure phase modulation in the transparency regime, where optical losses are minimized and remain constant with increasing voltage. Our device has VπL ∼ 0.3Vcm, matching state-of-the-art SLG-based MZMs and plasmonic LN MZMs, but with pure phase modulation and low insertion loss (∼5 dB), essential for IQ modulation. Our VπL is ∼5 times lower than the lowest thin-film LN MZMs and ∼3 times lower than the lowest Si MZMs. This enables devices with complementary metal-oxide semiconductor compatible VπL (<1Vcm) and smaller footprint than LN or Si MZMs, improving circuit density and reducing power consumption by 1 order of magnitude.

Broadband conversion between high-order angular modes based on double-sided exposure long-period fiber grating.

Broadband high-order mode converters play a fundamental and crucial role in mode division multiplexing systems. Unfortunately, there have been no reports on achieving broadband mutual conversion between high-order modes using long-period fiber gratings (LPFGs). In this paper, based on the concept of "stepwise" progressive conversion (SPC), a double-sided exposure fabrication method of LPFGs to achieve broadband mutual conversion between high-order modes is proposed and demonstrated. Based on the proposed method, broadband mode conversion from LP11 to LP21, from LP21 to LP31 and from LP31 to LP41 with low insertion loss are achieved by utilizing low exposure power and shortened device lengths. The 10 dB bandwidths of the three converters are measured to be 80 nm, 110 nm, and 90 nm, respectively, and their insertion losses are all less than 0.2 dB. Theoretically, this method can achieve broadband conversion of even higher-order modes, providing a novel solution for the fabrication of stable broadband mode converters. More generally, such mode converters can convert between any two modes and are essential for building advanced MDM networks that require routing and mode switching.

Compact design of universal gates with non-aligned gate technology and assessment of its performance in a TCAD Environment

ABSTRACT This paper proposes a technology computer-aided design (TCAD) of a compact single-device NAND and NOR logic gates in 215 nm device length along with speed and power performance results. The universal gates are designed with non-aligned double gate technology, and this helps to reduce the transistor count, giving a compact design structure. The static characteristics and input pattern sensitivity of the NAND and NOR structures are investigated in this work. By using graphical method, the optimal supply voltage of the universal gates was determined. The optimal supply voltage of the NAND gate and NOR gate was 0.9 V and 0.84 V, respectively, at an input frequency of 1 GHz. Further, the device scalability of the proposed structures was analysed. When compared to the past work, the proposed NAND gate and NOR gate improves delay performance by 25.02% and 35.63%, respectively. Additionally, a reduction of 10% and 16% in its supply voltage is achieved. Therefore, the proposed gate has potential to operate at higher frequency with reduced supply voltage, making them suitable in circuit applications.

Comparison of Clinical Outcomes between Drug-Eluting Balloons and Drug-Eluting Stents in Patients with Small Coronary Artery Disease

Background/Aims: Drug-eluting balloons (DEBs) represent a novel therapeutic approach for patients with small coronary artery disease. However, further studies are needed to compare the clinical efficacy of DEBs versus drug-eluting stents (DESs).Methods: In total, 492 patients (age, 67.9 ± 11.0 years; 339 men) with small coronary artery lesions (diameter &lt; 2.75 mm) were randomly assigned to group I (DEB) (n = 104; age, 67.2 ± 10.7 years; 83 men) and group II (DES) (n = 388; age, 68.0 ± 11.1 years; 254 men). For inverse probability of treatment weighting (IPTW) analysis, the study population was stratified into groups I (n = 269) and II (n = 280). We compared the incidences of major adverse cardiac events (MACE) between the two groups during 12 months of clinical follow-up.Results: Group I had shorter device lengths (22.4 ± 5.8 mm) compared with group II (27.4 ± 9.3 mm; p &lt; 0.001). Additionally, devices in group I were smaller in diameter (2.4 ± 0.1 mm) compared with those in group II (2.6 ± 0.1 mm; p &lt; 0.001). Left ventricular ejection fraction (LVEF) was lower in group I (53.8% ± 12.6%) than in group II (58.6% ± 11.9%; p &lt; 0.001). After IPTW, no significant differences in LVEF were observed between groups I and II. During 12 months of follow-up, the incidence of total MACE did not differ between the two groups.Conclusions: No significant differences were observed in clinical efficacy between DEB and DES for the treatment of small coronary artery disease. Therefore, DEB can be considered a viable alternative to DES in patients with small coronary artery disease.

Zero-crosstalk silicon photonic refractive indexsensor with subwavelength gratings.

Silicon photonic index sensors have received significant attention for label-free bio and gas-sensing applications, offering cost-effective and scalable solutions. Here, we introduce an ultra-compact silicon photonic refractive index sensor that leverages zero-crosstalk singularity responses enabled by subwavelength gratings. The subwavelength gratings are precisely engineered to achieve an anisotropic perturbation-led zero-crosstalk, resulting in a single transmission dip singularity in the spectrum that is independent of device length. The sensor is optimized for the transverse magnetic mode operation, where the subwavelength gratings are arranged perpendicular to the propagation direction to support a leaky-like mode and maximize the evanescent field interaction with the analyte space. Experimental results demonstrate a high wavelength sensitivity of - 410nm/RIU and an intensity sensitivity of 395dB/RIU, with a compact device footprint of approximately 82.8μm2. Distinct from other resonant and interferometric sensors, our approach provides an FSR-free single-dip spectral response on a small device footprint, overcoming common challenges faced by traditional sensors, such as signal/phase ambiguity, sensitivity fading, limited detection range, and the necessity for large device footprints. This makes our sensor ideal for simplified intensity interrogation. The proposed sensor holds promise for a range of on-chip refractive index sensing applications, from gas to biochemical detection, representing a significant step towards efficient and miniaturized photonic sensing solutions.