Tunable optical materials are indispensable elements in modern optoelectronics, especially in integrated photonics circuits where precise control over the effective refractive index is essential for diverse applications. Two-dimensional materials like transition metal dichalcogenides (TMDs) and graphene exhibit remarkable optical responses to external stimuli. However, achieving distinctive modulation across short-wave infrared (SWIR) regions while enabling precise phase control at low signal loss within a compact footprint remains an ongoing challenge. In this work, we unveil the robust electro-refractive response of multilayer ferroionic two-dimensional CuCrP2S6 (CCPS) in the near-infrared wavelength range. By integrating CCPS into silicon photonics (SiPh) microring resonators (MRR), we enhance light-matter interaction and measurement sensitivity to minute phase and absorption variations. Results show that electrically driven Cu ions can tune the effective refractive index on the order of 2.8 × 10-3 RIU (refractive index unit) while preserving extinction ratios and resonance linewidth. Notably, these devices exhibit low optical losses and excellent modulation efficiency of 0.25 V.cm with a consistent blue shift in the resonance wavelengths among all devices for either polarity of the applied voltage. These results outperform earlier findings on phase shifters based on TMDs. Furthermore, our study demonstrates distinct variations in electro-optic tuning sensitivity when comparing transverse electric (TE) and transverse magnetic (TM) modes, revealing a polarization-dependent response that paves the way for diverse applications in light manipulation. The combined optoelectronic and ionotronic capabilities of two-terminal CCPS devices present extensive opportunities across several domains. Their potential applications range from phased arrays and optical switching to their use in environmental sensing and metrology, optical imaging systems, and neuromorphic systems in light-sensitive artificial synapses.
The growing freshwater scarcity has caused increased use of membrane desalination of seawater as a relatively sustainable technology that promises to provide long-term solution for the increasingly water-stressed world. However, the currently used membranes for desalination on an industrial scale are inevitably prone to fouling that results in decreased flux and necessity for periodic chemical cleaning, and incur unacceptably high energy cost while also leaving an environmental footprint with unforeseeable long-term consequences. This extant problem requires an immediate shift to smart separation approaches with self-cleaning capability for enhanced efficiency and prolonged operational lifetime. Here, we describe a conceptually innovative approach to the design of smart membranes where a dynamic functionality is added to the surface layer of otherwise static membranes by incorporating stimuli-responsive organic crystals. We demonstrate a gating effect in the resulting smart dynamic membranes, whereby mechanical instability caused by rapid mechanical response of the crystals to heating slightly above room temperature activates the membrane and effectively removes the foulants, thereby increasing the mass transfer and extending its operational lifetime. The approach proposed here sets a platform for the development of a variety of energy-efficient hybrid membranes for water desalination and other separation processes that are devoid of fouling issues and circumvents the necessity of chemical cleaning operations.
The emergence of large language models has led to the development of powerful tools such as ChatGPT that can produce text indistinguishable from human-generated work. With the increasing accessibility of such technology, students across the globe may utilize it to help with their school work-a possibility that has sparked ample discussion on the integrity of student evaluation processes in the age of artificial intelligence (AI). To date, it is unclear how such tools perform compared to students on university-level courses across various disciplines. Further, students' perspectives regarding the use of such tools in school work, and educators' perspectives on treating their use as plagiarism, remain unknown. Here, we compare the performance of the state-of-the-art tool, ChatGPT, against that of students on 32 university-level courses. We also assess the degree to which its use can be detected by two classifiers designed specifically for this purpose. Additionally, we conduct a global survey across five countries, as well as a more in-depth survey at the authors' institution, to discern students' and educators' perceptions of ChatGPT's use in school work. We find that ChatGPT's performance is comparable, if not superior, to that of students in a multitude of courses. Moreover, current AI-text classifiers cannot reliably detect ChatGPT's use in school work, due to both their propensity to classify human-written answers as AI-generated, as well as the relative ease with which AI-generated text can be edited to evade detection. Finally, there seems to be an emerging consensus among students to use the tool, and among educators to treat its use as plagiarism. Our findings offer insights that could guide policy discussions addressing the integration of artificial intelligence into educational frameworks.
Artificial Intelligence , Communication , Humans , Universities , Schools , Perception
An efficient, dual-polarization silicon waveguide array with low insertion losses and negligible crosstalks for both TE and TM polarizations has been reported using S-shaped adiabatically bent waveguides. Simulation results for a single S-shaped bend show an insertion loss (IL) of ≤ 0.03 dB and ≤ 0.1 dB for the TE and TM polarizations, respectively, and TE and TM crosstalk values in the first neighboring waveguides at either side of the input waveguide are lower than -39 dB and -24 dB, respectively, over the wavelength range of 1.24 µm to 1.38 µm. The bent waveguide arrays exhibit a measured average TE IL of ≈ 0.1 dB, measured TE crosstalks in the first neighboring waveguides are ≤ -35 dB, at the 1310 nm communication wavelength. The proposed bent array can be made by using multiple cascaded S-shaped bends to transmit signals to all optical components in integrated chips.
The outstanding performance and facile processability turn two-dimensional materials (2DMs) into the most sought-after class of semiconductors for optoelectronics applications. Yet, significant progress has been made toward the hybrid integration of these materials on silicon photonics (SiPh) platforms for a wide range of mid-infrared (MIR) applications. However, realizing 2D materials with a strong optical response in the NIR-MIR and excellent air stability is still a long-term goal. Here, we report a waveguide integrated photodetector based on a novel 2D GeP. This material uniquely combines narrow and wide tunable bandgap energies (0.51-1.68 eV), offering a broadband operation from visible to MIR spectral range. In a significant advantage over graphene devices, hybrid Si/GeP waveguide photodetectors work under bias with a low dark current of few nano-amps and demonstrate excellent stability and reproducibility. Additionally, 65 nm thick GeP devices integrated on silicon waveguides exhibit a remarkable photoresponsivity of 0.54 A/W and attain high external quantum efficiency of â¼ 51.3% under 1310 nm light and at room temperature. Furthermore, a measured absorption coefficient of 1.54 ± 0.3 dB/µm at 1310 nm suggests the potential of 2D GeP as an alternative infrared material with broad optical tunability and dynamic stability suitable for advanced optoelectronic integration.
We demonstrate a novel TE-pass polarizer, to the best of our knowledge, on a silicon-on-insulator (SOI) platform. The device's working principle is based on the phase-matched coupling of the unwanted TM0 mode in an input waveguide to the TM1 mode in a tapered directional coupler (DC), which is then guided through a low-loss bend (180-degree) and scattered in a terminator section with low back reflections. However, the input TE0 mode is routed through the tapered section uncoupled with negligible loss. An S-bend is added before the output for filtering any residual TM0 mode present in the input waveguide. Tapering the DC helps maintain phase matching for broadband operation and increases the tolerance toward fabrication errors. The measurement shows low insertion loss (IL < 0.44â dB), high extinction ratio (ER > 15â dB), and wide bandwidth (BW = 80â nm). The overall device length is only 13â µm. A high performing TE-pass polarizer (IL < 0.89, ER > 30, and BW = 100â nm) is also demonstrated by cascading two proposed polarizers.
Dynamic organic crystals are rapidly gaining traction as a new class of smart materials for energy conversion, however, they are only capable of very small strokes (<12%) and most of them operate through energetically cost-prohibitive processes at high temperatures. We report on the exceptional performance of an organic actuating material with exceedingly large stroke that can reversibly convert energy into work around room temperature. When transitioning at 295-305 K on heating and at 265-275 K on cooling the ferroelectric crystals of guanidinium nitrate exert a linear stroke of 51%, the highest value observed with a reversible operation of an organic single crystal actuator. Their maximum force density is higher than electric cylinders, ceramic piezoactuators, and electrostatic actuators, and their work capacity is close to that of thermal actuators. This work demonstrates the hitherto untapped potential of ionic organic crystals for applications such as light-weight capacitors, dielectrics, ferroelectric tunnel junctions, and thermistors.
A compact, ultra-broadband and high-performance silicon TE-pass polarizer is proposed and demonstrated experimentally. It is based on partially-etched (ridge) waveguide adiabatic S-bends, input/output tapers and side gratings on a silicon-on-insulator (SOI) platform. A compact footprint and weak back reflections are obtained due to the bent waveguide and the tapers, respectively. An extremely high extinction ratio is achieved by scattering the undesired light in the slab section using the side gratings. The 3D FDTD simulations show a TE loss less than 0.3 dB and an extinction ratio greater than 30 dB over a 500 nm wavelength range (1200 nm to 1700 nm). Measured results show a high TM loss (> 35 dB) and a low TE insertion loss (< 1.5 dB), over a 200 nm wavelength range (1450 nm to 1650 nm). The measured TE loss is < 0.6 dB at a communication wavelength of 1550 nm. The footprint of the optimized design is 65 µm × 20 µm.
We design and experimentally demonstrate an ultra-compact 1310/1550 nm wavelength diplexer based on a multimode interference (MMI) coupler. The proposed device is designed at the first imaging length for 1550 nm wavelength resulting in an MMI length of only 41 µm. In order to improve the extinction ratio, the output ports are made asymmetric in width. A low insertion loss (< 1dB) and high extinction ratio (> 20 dB) is measured at the two operating wavelengths. It also displays a wide 3-dB bandwidth of 100 nm centered around 1310 nm and 1550 nm wavelengths. Furthermore, an on-chip wavelength demultiplexing experiment carried out on the fabricated device, with a non-return-to-zero (NRZ) on-off keying (OOK) signal at 60 Gbit/s, shows clear eye diagrams for both the wavelengths.
The outstanding performance and facile processability turn hybrid organic-inorganic perovskites into one of the most sought-after classes of semiconducting materials for optoelectronics. Yet, their translation into real-world applications necessitates that challenges with their chemical stability and poor mechanical robustness are first addressed. Here, centimeter-size single crystals of methylammoniumlead(II) iodide (MAPbI3 ) are reported to be capable of autonomous self-healing under minimal compression at ambient temperature. When crystals are halved and the fragments are brought in contact, they can readily self-repair as a result of a liquid-like behavior of their lattice at the contact surface, which leads to a remarkable healing with an efficiency of up to 82%. The successful reconstitution of the broken single crystals is reflected in recuperation of their optoelectronic properties. Testing of the healed crystals as photodetectors shows an impressive 74% recovery of the generated photocurrent relative to pristine crystals. This self-healing capability of MAPbI3 single crystals is an efficient strategy to overcome the poor mechanical properties and low wear resistance of these materials, and paves the way for durable and stable optoelectronic devices based on single crystals of hybrid perovskites.
Recent theoretical studies proposed that two-dimensional (2D) GaGeTe crystals have promising high detection sensitivity at infrared wavelengths and can offer ultra-fast operation. This can be attributed to their small optical bandgap and high carrier mobility. However, experimental studies on GaGeTe in the infrared region are lacking and this exciting property has not been explored yet. In this work, we demonstrate a short-wavelength infrared (SWIR) photodetector based on a multilayer (ML) GaGeTe field-effect transistor (FET). Fabricated devices show a p-type behavior at room temperature with a hole field-effect mobility of 8.6 - 20 cm2 V-1s-1. Notably, under 1310 nm illumination, the photo responsivities and noise equivalent power of the detectors with 65 nm flake thickness can reach up to 57 A/W and 0.1 nW/Hz1/2, respectively, at a drain-source bias (Vds) = 2 V. The frequency responses of the photodetectors were also measured with a 1310 nm intensity-modulated light. Devices exhibit a response up to 100 MHz with a 3dB cut-off frequency of 0.9 MHz. Furthermore, we also tested the dependence of the device frequency response on the applied bias and gate voltages. These early experimental findings stimulate the potential use of multilayer GaGeTe for highly sensitive and ultrafast photodetection applications.
We present an experimental analysis of optical Physically Unclonable Functions enhanced using plasmonic metal nanoparticles in a Silicon on Insulator based integrated structure. We experimentally demonstrate the behavior of possible configurations of simple PUF structures defined only by the nanoparticle distribution. The devices show a promising response when tested with transverse magnetic polarized light. This response offers an easy-to-implement methodology to enhance the behavior of previously proposed optical PUFs. We additionally make a comprehensive analysis of the power, thermal, and polarization stability of the devices for possible side-channels attacks to the systems.
We report the first organic semiconductor crystal with a unique combination of properties that can be used as a multifunctional optoelectronic device. Mechanically flexible single crystals of 9,10-bis(phenylethynyl)anthracene (BPEA) can function as a phototransistor, photoswitch, and an optical waveguide. The material can exist as two structurally different solid phases, with single crystals of one of the phases being elastic at room temperature while those of the other are brittle and become plastic at higher temperature. The output and transfer characteristics of the devices were characterized by measuring the generation and temporal response of the switching of the photogenerated current. The current-voltage characteristics of both phases exhibit linearity and symmetry about the positive and negative voltages. The crystals transmit light in the telecommunications range with significantly low optical loss for an organic crystalline material.
We report an all-silicon thermally insensitive (-1.5pm/∘C) 2×2 Mach-Zehnder interferometer (MZI) over a spectral range from 1540 to 1620 nm. Additionally, the proposed MZI exhibits no imbalance in its extinction ratio with temperature. The broadband spectral range with minimal temperature sensitivity is achieved by slightly overcompensating the MZI design for temperature variations. At the same time, the uniformity in the extinction ratio is controlled using sub-wavelength grating adiabatic couplers for splitting and combining.
Novel group IV - V 2D semiconductors (e.g., GeAs and SiAs) have arisen as an attractive candidate for broad-band photodetection and optoelectronic applications. This 2D family has a wide tunable band gap, excellent thermodynamic stability, and strong in-plane anisotropy. However, their photonic and optoelectronic properties have not been extensively explored so far. This work demonstrates a broadband back-to-back metal-semiconductor-metal (MSM) Schottky photodiode with asymmetric contact geometries based on multilayered 2D GeAs. The photodetector exhibited a Schottky barrier height (SBH) in the range of 0.40-0.49 eV. Additionally, it showed a low dark current of 1.8 nA with stable, reproducible, and excellent broadband spectral response from UV to optical communication wavelengths. The highest measured responsivity in the visible is 905 A/W at 660 nm wavelength and 98 A/W for 1064 nm near-infrared at an applied voltage of -3 V and zero back gate. Most notably, the planner configuration of this GeAs photodetector showed a low detector capacitance below 1.2 pf and low voltage operation (<1 V). The stability and broadband response of the device are promising for this 2D material's application in advanced optoelectronic devices.
Layered two-dimensional (2D) materials with broadband photodetection capability have tremendous potential in the design and engineering of future optoelectronics devices. To date, studies of 2D semiconductors are actively focused on graphene, black phosphorus, and black arsenic phosphorus as attractive candidates. So far, however, novel group IV-V 2D semiconductors (e.g., GeAs and SiAs) have not been extensively explored for broad-band optoelectronics applications. Here, we report a high-performance multilayered 2D GeP gate-tunable photodetector that operates at a short-wavelength infrared (SWIR) regime. With a back-gate device geometry, a p-type behavior is observed at room temperature. Furthermore, a broadband spectral response from UV to optical communication wavelengths is detected. Under a nanowatt-level illumination, a peak responsivity of 25.5 A/W at λ = 1310 nm is achieved with detectivity of â¼ 1×1011 cm.Hz1/2.W-1 at a source-drain bias of -5 V and medium gate voltage bias of -30 V. Additionally, the devices show a relatively low dark current of 40-250 nA for device area in the range of 50-600 µm2 and excellent stability and reproducibility. Our work demonstrates the potential of 2D GeP as an alternative mid-infrared material with broad optical tunability suitable for optical communication and low-light-level detection applications.
Graphene has emerged as an ultrafast optoelectronic material for all-optical modulators. However, because of its atomic thickness, it absorbs a limited amount of light. For that reason, graphene-based all-optical modulators suffer from either low modulation efficiencies or high switching energies. Through plasmonic means, these modulators can overcome the aforementioned challenges, yet the insertion loss (IL) of plasmon-enhanced modulators can be a major drawback. Herein, we propose a plasmon-enhanced graphene all-optical modulator that can be integrated into the silicon-on-insulator platform. The device performance is quantified by investigating its switching energy, extinction ratio (ER), IL, and operation speed. Theoretically, it achieves ultrafast (<120 fs) and energy-efficient (<0.6 pJ) switching. In addition, it can operate with an ultra-high bandwidth beyond 100 GHz. Simulation results reveal that a high ER of 3.5 dB can be realized for a 12 µm long modulator, yielding a modulation efficiency of â¼0.28 dB/µm. Moreover, it is characterized by a 6.2 dB IL, which is the lowest IL reported for a plasmon-enhanced graphene all-optical modulator.
Organic crystals are emerging as mechanically compliant, light-weight and chemically versatile alternatives to the commonly used silica and polymer waveguides. However, the previously reported organic crystals were shown to be able to transmit visible light, whereas actual implementation in telecommunication devices requires transparency in the near-infrared spectral range. Here we demonstrate that single crystals of the amino acid L-threonine could be used as optical waveguides and filters with high mechanical and thermal robustness for transduction of signals in the telecommunications range. On their (00[Formula: see text]) face, crystals of this material have an extraordinarily high Young's modulus (40.95 ± 1.03 GPa) and hardness (1.98 ± 0.11 GPa) for an organic crystal. First-principles density functional theory calculations, used in conjunction with analysis of the energy frameworks to correlate the structure with the anisotropy in the Young's modulus, showed that the high stiffness arises as a consequence of the strong charge-assisted hydrogen bonds between the zwitterions. The crystals have low optical loss in the O, E, S and C bands of the spectrum (1250-1600 nm), while they effectively block infrared light below 1200 nm. This property favors these and possibly other related organic crystals as all-organic fiber-optic waveguides and filters for transduction of information.
Amino Acids/chemistry , Communication , Fiber Optic Technology/methods , Transducers , Anisotropy , Crystallization , Crystallography, X-Ray , Elastic Modulus , Hardness , Hydrogen Bonding , Threonine/chemistry
Strain engineering of germanium has recently attracted tremendous research interest. The primary goal of this approach is to exploit mechanical strain to tune the electrical and optical properties of Ge to ultimately achieve an on-chip light source compatible with silicon technology. Additionally, this can result in enhanced electrical performance for high-speed optoelectronic applications. In this paper, we demonstrate the formation of highly tensile-strained Ge islands grown on a pre-patterned (110) GaAs substrate using a depth controlled nanoindentation process. Results show that a biaxial tensile strain, up to â¼2%, can be transferred from the mechanically stamped substrate to Ge islands by optimizing the parameters of the nanoindentation process. We verified our measurements by observing the islands' photoluminescence (PL) emission properties. A strong emission at room-temperature was observed around the wavelength of 1.9 µm (650 meV). This strain-induced redshift of the PL spectra is consistent with theoretical predictions, revealing a direct Ge bandgap formation. Furthermore, we demonstrate a significant 6.5x enhancement in the PL emission signal of the direct-transition when the Ge islands are decorated by 5 nm gold nanoparticles. This is attributed to a longer optical path length interaction and a plasmonic induced high-field enhancement which increases the light absorption in the Ge islands. Furthermore, results show that GNPs can significantly modulate the energy band structure and the carrier's transportation at the nanoscale metal-germanium Schottky interface. This maskless physical approach can offer a pathway towards a practical CMOS-compatible integrated laser. Additionally, it opens possibilities for designing innovative optoelectronic devices.
