Photonic Systems Research Articles

The transformational dive of nanophotonics inverse design from deep learning to artificial general intelligence

The swift development of artificial intelligence (AI) is significantly transforming the paradigm of nanophotonics. Leveraging universal approximation abilities, AI models sidestep time-consuming electromagnetic simulations, opening the inverse design of photonics systems with millions of design features while offering ample stability and practical scalability compared to traditional optimization methods. This perspective discusses inverse design paradigms enabled by recent advances in AI models, discussing their roles, challenges, and opportunities envisioned by the approaching era of artificial general intelligence.

Isolator-free quantum dot comb lasers with optical feedback enhanced DWDM transmission

Feedback-insensitive Quantum Dot (QD) comb lasers hold significant promise for integrated dense wavelength division multiplexing photonic systems due to their ability to generate multiple wavelengths and operate without bulky isolators, facilitating the development of high-density and large-scale photonic integrated circuits. In this study, we investigated the optical feedback (OFB) influence of the InAs/GaAs QD comb laser from various perspectives. Our findings reveal that the comb laser exhibits a stable locking region with consistent optical spectra across a range of OFB strengths (−45 to −10 dB). Furthermore, under a high OFB strength of −10 dB, there is a notable 40 dB suppression of relative intensity noise in the low-frequency range (below 1 GHz). Transmission experiments demonstrate clear eye openings at 25 Gbps using a bit pattern of 231-1 pseudorandom binary sequence. Remarkably, the bit error rates decrease by five orders of magnitude under −10 dB OFB. These results indicate the ultra-robustness of 100 GHz grid QD comb laser, which exhibits great transmission enhancement under a strong OFB of −10 dB.

Do spectral reflectance indices distinguish between the greenness in three different moss species in moss banks on Galindez Island (Argentine Islands)?

Spectral reflectance indices of green state of Warnstorfia fontinaliopsis, Chorisodontium aciphyllum and Sanionia georgicouncinata on moss bank in the Galindez Island (Argentine Islands) were measured using a handheld spectrometer PolyPen RP 410 UVIS (Photon Systems Instruments, Drásov, Czech Republic) within the range of 380–790 nm in order to find suitable ones for effective classification of moss species within the same colour state (green). Among altogether 19 indices tested, there were some which did not differ significantly between the studied species (subgroup 1). Other indices (subgroup 2) were sensitive enough to distinguish one of the studied species from the others, and finally (subgroup 3), they were found statistically significantly different for all studied moss species. Also, the indices calculated at wavelengths typical for UAV spectral cameras (green, red and red edge channels) showed species-specific differences and can be potentially used to distinguish between different mosses within the same green physiological state indicating a good vigor.

Millimeter wave frequency generation based on variations in coupling coefficients of a silicon add-drop microring resonator

A microwave photonic system with silicon add-drop microring resonator as the core photonic device is analyzed for microwave/millimeter wave frequency generation. The primary concept of the proposed study relies on varying the coupling coefficients of the silicon add-drop microring resonator. Unequal coupling coefficients between the ring cavity and bus waveguides are one of the parameters which are responsible for generating second, third order sidebands in the radio frequency spectrum generated at the photodetector. Another parameter of interest is the phase difference between the two radio frequency signals which are fed to the Mach–Zehnder modulators of the proposed system. A 1 GHz sinusoidal signal with 1V peak-to-peak amplitude results in a third order sideband generation whose frequency corresponds to 3 GHz. The coupling coefficients in this case are 0.2 and 0.8, between ring cavity, top and bottom waveguides respectively. It is also observed that, phase difference of 90◦ between the input radio frequency signals results in highest power of the third order sideband generated in the output radio frequency spectrum whose frequency corresponds to the multiple of input radio frequency.

Two-Dimensional Supramolecular Polymorphism in Cyanine H- and J-Aggregates.

We designed a new cyanine dye 1, with two pedant rod-like groups, capable of forming two distinct two-dimensional (2D) supramolecular polymorphs in methylcyclohexane; an H-type aggregate (Agg-H2) and a J-type aggregate (Agg-J). Importantly, these two polymorphs were not accessed through polymerization events, and instead through the thermal transformation of a third particle-like polymorph (Agg-H1) formed by the anti-cooperative assembly of 1. While Agg-H2 is generated upon cooling the solution of Agg-H1 by a thermoreversible polymorph transition, the Agg-J was obtained through a hidden pathway by combining sonication and cooling to the Agg-H1 solution. This is the first report on the obtention of H- and J-type cyanine polymorphs that in turn could be isolated in solid-state to render two new 2D photoactive materials. This paper unveils new strategies for designing 2D supramolecular polymers using calamitic residues, but also undercovers relevant aspects of pathway complexity and polymorph transitions that might be crucial for developing novel photonic systems.

Realization of quantum secure direct communication by Kitaev Abelian anyons

The quantum secure direct communication (QSDC) is provably secure and has a high capacity. The QSDC protocols are usually experimented in photon systems. Here we propose four schemes to realize the QSDC in the Kitaev Abelian anyon model: 1) the two-step scheme, 2) 2⊗2 dimensional superdense coding scheme, 3) the hyperentanglement-assisted one-step scheme and 4) one-time pad scheme. Our work provides a possibility to implement the quantum secure direct communication in many-body systems and gives a new research perspective of the quantum information on the unitary evolution of quantum field systems.

Chirped grating for TE-five/TM-three reflective distribution feature

This research expounds on a novel reflective chirped grating, characterized by its differentiated functionality under various polarization modes. Under perpendicular incidence, this intricately grating produces a quintuple-channel diffraction output of the 0th, ±1st, and ±2nd orders in transverse electric (TE) polarization and a triple-channel diffraction output of the 0th and ±1st orders in transverse magnetic (TM) polarization. Both polarization modes exhibit excellent overall diffraction efficiency and uniformity. At an incident wavelength of 1550 nm, the diffraction efficiencies for the 0th, ±1st, and ±2nd orders under TE polarization are 20.16%, 19.27%, and 20.25%, respectively. Simultaneously, under TM polarization, the efficiencies for the 0th and ±1st orders are 31.79% and 31.57%, respectively. Grating parameters were meticulously derived using the finite element method (FEM) and subsequently corroborated through rigorous coupled-wave analysis (RCWA) to ensure superior grating accuracy. The study also exhaustively analyzes the manufacturing tolerances and robustness of the grating, affirming its practical applicability and effectiveness in practical applications. The dual-function grating splitter proposed in this paper enables the implementation of multiple functionalities within simple setups, suitable for applications requiring varied beam splitting. As photonic systems and fiber technology evolve, the potential applications of dual-function reflective splitters in these fields are increasingly highlighted.

Broadband low-loss polarization-insensitive graphene-integrated photonic crystal fiber modulators in the near-infrared range

The amplitude modulator with the function of converting electric signal to optical amplitude modulation is a key component in high-speed optical communication links. In this paper, we demonstrate a variety of two-dimensional graphene-integrated photonic crystal fiber modulators for efficient near-infrared amplitude modulation with ultra-low insertion loss. Taking the advantages of the perfect total internal reflection of the porous photonic crystal fiber and flexible tunability of the graphene conductivity, the modulation depth of 0.075 dB μm−1 with a low optical loss of 2.13 × 10−4 dB μm−1, a long propagation length of ∼20 mm and polarization-insensitive characteristics in a wide wavelength of 1.3 to 1.8 μm can be achieved. This high-performance modulator may have great potential applications in various high-speed telecommunication, interconnection, and graphene-based integrated photonic systems.

Subsymmetry protected topology in topological insulators and superconductors

Exploration of topology protected by a certain symmetry is central in condensed matter physics. A recent idea of subsymmetry protected (SSP) topology—remains of a broken symmetry can still protect specific topological boundary states—has been developed and demonstrated in a photonic system [], but not in topological superconductors. Here, we extend this idea further by applying subsymmetry protecting perturbation (SSPP) to one-dimensional topological insulating and superconducting systems using the Su-Schrieffer-Hegger (SSH) and Kitaev models. Using the tight-binding and low-energy effective theory, we show that the SSP boundary states retain topological properties while the SSPP results in the asymmetry of boundary states. For the SSH model, an SSP zero-energy edge state localized on one edge possesses quantized polarization. In contrast, the other edge state is perturbed to have nonzero energy, and its polarization is not quantized. For topological superconductors, SSP zero-energy Majorana boundary states for spinful Kitaev models emerge on only one edge, contrary to the conventional belief that Majorana fermions emerge at opposite edges. Our findings can be used as a platform to expand our understanding of topological materials as they broaden our understanding of the symmetry in a topological system and a method to engineer Majorana fermions. Published by the American Physical Society 2024

Realizing a kilowatt-level fiber amplifier with a 42 μm core diameter fiber for improved multi-mode performance towards single mode operation output through adaptive spatial mode control utilizing a 3×1 photonic lantern

The photonic lantern, a coherent beam combiner capable of controlling the phase, amplitude, and polarization of input light, has been utilized to enhance the brightness of fiber lasers by managing the output beam’s mode. In this work, a 3×1 photonic lantern-based adaptive spatial mode control system is employed to realize kilowatt-level operation in a 42 μm core fiber laser amplifier. Both simulation and experimental outcomes affirm the ability of this approach to manage modes within large-mode-area fiber laser systems through the use of 3 input arms. The experiment not only streamlines the overall system design but also has the potential to reduce production costs and complexities. Additionally, the spectrum width has been optimized to 10 GHz, striking a balance between the SBS threshold and the coherence of the photonic lantern’s input arms. By implementing this system, we have successfully achieved a stable, improved multi-mode performance towards single mode operation output of 1.08 kW, with a beam quality factor M2 of 2.20. This research furthers our understanding of how photonic lanterns can stabilize and enhance beam quality in high-power fiber lasers, paving the way for potential improvements in their performance and applications.

Pressure Visualization and Quantification Photonic Skin Based on Flexible Optical Fiber Combiner

AbstractThe integration of pressure quantification and visualization enhances pressure perception, accuracy, and efficiency. Current solutions require improvements in quantization accuracy, structural simplicity, and integration. We proposed a novel photonic skin comprising a 3 × 1 flexible optical fiber combiner, integrating red, green, and blue light emitting diode (LED) chips through three flexible optical fibers. Under pressure, changes in the optical fibers' transmission loss alter the output light intensity ratio, thus inducing a color shift at the combiner's output. This visible change can be precisely quantified using a color sensor chip. Performance metrics include sensing range up to 33N, sensitivity between 0.04 and 0.24 dB N−1, detection limit below 0.08 N, response time of 500 ms, recovery time of 400 ms, and durability exceeding 2000 cycles. A compact flexible circuit board manages light source driving, data acquisition, and wireless communication, forming a wearable photonic skin system. This system enables visual recognition and quantitative measurement of pressure across diverse scenarios, including different tactile modes, multi‐position pressure, finger bending, and neck movement. For oral occlusion force detection, the spatial separation of the sensing and visualization areas enables the system to simultaneously provide accurate measurements and intuitive visual assessment.

Compact and low-crosstalk multimode waveguide crossing utilizing subwavelength holey metamaterial waveguides

To further increase the transmission capacity of on-chip optical communication systems, hybrid division multiplexing technology has emerged as a crucial alternative solution, in which multimode waveguide crossings are highly desired. In this paper, we propose and experimentally demonstrate a compact multimode (i.e., three different modes) waveguide crossing that employs subwavelength holey metamaterial waveguides (SHMWs). The used SHMW, formed by inserting subwavelength periodic holes into a multimode interference (MMI) coupler, deservedly exhibits synergetic advantages of the two kinds of structures, enabling an attractive three-mode (e.g., TE0, TM0, and TM1) waveguide crossing with flexible design, small size, and good performance. Simulation results show that the realized device has a low insertion loss (< 0.74 dB), low reflection loss (<−13.1 dB), and low crosstalk (<−31.6 dB) at a central wavelength of 1550 nm for all the modes with a compact footprint of 27.4 µm × 27.4 µm. The experimental results prove that insertion losses are as low as 0.72 dB, 0.27 dB, and 0.90 dB for TE0, TM0, and TM1 mode, respectively, with the corresponding crosstalk below −38 dB at 1550 nm. The proposed device can be widely applied in photonic integrated circuits to construct photonic systems with the abilities of mode control and multiplexing.

Polarization-dependent near-field coupling and far-field harmonic modulation in a graphene-based plasmonic nanostructure

The interplay between light and matter has fostered innovative research in surface plasmons, specifically in graphene, due to its tunable Fermi energy and reduced losses in the infrared and terahertz spectra. This study explores the anisotropic coupling of nonlocalized surface plasmons in graphene with localized magnetic polaritons (MP) in a silicon carbide (SiC) array. By adjusting graphene’s Fermi energy and polarization angle, we successfully achieved hybrid coupling, giving rise to three clearly distinguishable hybridized states. Using the coupled oscillator model as a framework, we conducted an analysis of the intricate multimode coupling and accurately ascertained the weighting efficiencies of the individual modes comprising the hybrids. By integrating the design principles of space-time coding metasurfaces, we successfully broadened the scope of the application, extending its reach from the near-field to the far-field. These novel discoveries pave new paths for advancements in thermal emitters, photonic systems, energy conversion technologies, and the creation of cutting-edge plasmonic devices.

Temperature dependence of optical phase transitions in a system of two-level atoms and photons interacting inside a nonlinear cavity

Temperature dependence of optical phase transitions in a system of two-level atoms and photons interacting inside a nonlinear cavity

Four-qubit photonic system for publicly verifiable quantum random numbers and generation of public and private key

Four-qubit photonic system for publicly verifiable quantum random numbers and generation of public and private key

High-coherence parallelization in integrated photonics

Coherent optics has profoundly impacted diverse applications ranging from communications, LiDAR to quantum computations. However, developing coherent systems in integrated photonics comes at great expense in hardware integration and energy efficiency. Here we demonstrate a high-coherence parallelization strategy for advanced integrated coherent systems at minimal cost. By using a self-injection locked microcomb to injection lock distributed feedback lasers, we achieve a record high on-chip gain of 60 dB with no degradation in coherence. This strategy enables highly coherent channels with linewidths down to 10 Hz and power over 20 dBm. The overall electrical-to-optical efficiency reaches 19%, comparable to that of advanced semiconductor lasers. This method supports a silicon photonic communication link with an unprecedented data rate beyond 60 Tbit/s and reduces phase-related DSP consumption by 99.99999% compared to traditional III-V laser pump schemes. This work paves the way for realizing scalable, high-performance coherent integrated photonic systems, potentially benefiting numerous applications.

Microsaccades Tracking by Secondary Speckle Pattern Analysis.

Here we propose a not pupil-dependent microsaccades tracking technique and a novel detection method. We present a proof of concept for detecting microsaccades using a non-contact laser-based photonic system recording and processing the temporal changes of speckle patterns scattered from an eye sclera. The data, simultaneously recorded by the speckle-based tracker (SBT) and the video-based eye tracker (Eyelink), was analyzed by the frequently used detection method of Engbert and Kliegl (E&K) and by advanced machine learning detection (MLD) techniques. We detected 93% of microsaccades in the SBT data out of microsaccades detected in the Eyelink data with the E&K method. By utilizing MLD, a precision of 86% was achieved. The findings of our study demonstrate a potential improvement in measuring tiny eye movements, such as microsaccades, using speckle-based eye tracking and, thus, an alternative to video-based eye tracking for detecting microsaccades.

Nonadiabatic nonlinear non-Hermitian quantized pumping

We analyze a quantized pumping in a nonlinear non-Hermitian photonic system with nonadiabatic driving. The photonic system is made of a waveguide array, where the distances between adjacent waveguides are modulated. It is described by the Su-Schrieffer-Heeger model together with a saturated nonlinear gain term and a linear loss term. A topological interface state between the topological and the trivial phases is stabilized by the combination of a saturated nonlinear gain term and a linear loss term. We study the pumping of the topological interface state. We define the transfer-speed ratio ω/Ω by the ratio of the pumping speed ω of the center of mass of the wave packet to the driving speed Ω of the topological interface. It is quantized topologically as ω/Ω=1 in the adiabatic limit. It remains to be quantized dynamically unless the driving is not too fast even in the nonadiabatic regime. On the other hand, the wave packet collapses and there is no quantized pumping when the driving is too fast. In addition, the stability against disorder is more enhanced by stronger nonlinearity. Published by the American Physical Society 2024

Telecom-band multiwavelength vertical emitting quantum well nanowire laser arrays

Highly integrated optoelectronic and photonic systems underpin the development of next-generation advanced optical and quantum communication technologies, which require compact, multiwavelength laser sources at the telecom band. Here, we report on-substrate vertical emitting lasing from ordered InGaAs/InP multi-quantum well core–shell nanowire array epitaxially grown on InP substrate by selective area epitaxy. To reduce optical loss and tailor the cavity mode, a new nanowire facet engineering approach has been developed to achieve controlled quantum well nanowire dimensions with uniform morphology and high crystal quality. Owing to the strong quantum confinement effect of InGaAs quantum wells and the successful formation of a vertical Fabry–Pérot cavity between the top nanowire facet and bottom nanowire/SiO2 mask interface, stimulated emissions of the EH11a/b mode from single vertical nanowires from an on-substrate nanowire array have been demonstrated with a lasing threshold of ~28.2 μJ cm−2 per pulse and a high characteristic temperature of ~128 K. By fine-tuning the In composition of the quantum wells, room temperature, single-mode lasing is achieved in the vertical direction across a broad near-infrared spectral range, spanning from 940 nm to the telecommunication O and C bands. Our research indicates that through a carefully designed facet engineering strategy, highly ordered, uniform nanowire arrays with precise dimension control can be achieved to simultaneously deliver thousands of nanolasers with multiple wavelengths on the same substrate, paving a promising and scalable pathway towards future advanced optoelectronic and photonic systems.

Nonequilibrium quasiparticle distribution in superconducting resonators: Effect of pair-breaking photons

Many superconducting devices rely on the finite gap in the excitation spectrum of a superconductor: thanks to this gap, at temperatures much smaller than the critical one the number of excitations (quasiparticles) that can impact the device’s behavior is exponentially small. Nevertheless, experiments at low temperature usually find a finite, non-negligible density of quasiparticles whose origin has been attributed to various non-equilibrium phenomena. Here, we investigate the role of photons with energy exceeding the pair-breaking threshold 2\Delta2Δ as a possible source for these quasiparticles in superconducting resonators. Modeling the interacting system of quasiparticles, phonons, sub-gap and pair-breaking photons using a kinetic equation approach, we find analytical expressions for the quasiparticles’ density and their energy distribution. Applying our theory to measurements of quality factor as function of temperature and for various readout powers, we find they could be explained by assuming a small number of photons above the pair-breaking threshold. We also show that frequency shift data can give evidence of quasiparticle heating.