On-chip Components Research Articles

Ge2Sb2Se4Te on n = 1 ITO: a monolithic platform for integrated photonics with mode symmetrization and post-fabrication tuning

We demonstrate, to our knowledge, a novel monolithic platform for photonic integrated circuits (PICs) based on amorphous-Ge2Sb2Se4Te (am-GSST). Additionally, we explore the concept of mode symmetrization using the epsilon-near-zero behavior displayed by indium-tin-oxide (ITO) to achieve a substrate with n=1 at 1550 nm, the same as the air cladding. We designed, fabricated, and characterized various on-chip components using this platform, including waveguides with preliminary 5.57±0.365dB/mm propagation loss. Furthermore, we propose a post-fabrication tuning of the refractive index by using the phase change nature of GSST to crystallize local sections of the waveguides using electron beams. Our substrate-blind approach is a versatile platform for post-fabrication tunable PICs that could benefit intricate on-chip nanophotonic structures requiring enhanced and symmetric mode confinement.

Rapid, non-contact identification of organic solvents: Monolithic GaN chips incorporating PDMS/PS photonic crystals

The prompt identification of organic solvents is essential in many practical scenarios. This work introduces a compact optical device for rapid, non-contact detection of organic solvents. The fabrication of the GaN chip employs a monolithic integration approach, enabling the simultaneous formation of on-chip components responsible for light emission and light detection. The self-assembled polystyrene (PS) spheres embedded in a polydimethylsiloxane (PDMS) layer as photonic crystals can effectively induce distinct optical changes when exposed to organic solvents. By analyzing the magnitude and recovery time of the photocurrent signals, up to seven types of organic samples can be distinguished. Different from traditional optical sensing systems, the proposed chip-level integration strategy eliminates the need for external assembly of optical components, resulting in an ultracompact millimeter-sized sensing unit. The developed device also offers features of simplicity of use and a short measurement time of less than 10 s, making it a feasible solution for quick detection in emergency scenarios.

(Invited) Eu- Oxide and Oxyhydroxide Nanofilms for Luminescent Photonic Components

Optically-doped rare-earth (RE) nanostructures find application in a diverse range of fields, including lighting (e.g. LEDs), displays, quantum memories, and biosensors such as luminescent nano-thermometers [1-5]. This is possible thanks to the ability of RE ions to provide robust and reliable light emission when incorporated in a solid. Since their performance depends critically on the composition and structure of the host material in order to successfully implement these RE-doped solids in technological applications it is desirable to achieve the controlled growth of low dimensional nanostructures that show efficient emission. This will enable on-chip component fabrication and their integration in photonic devices. The starting point of such technological development is the preparation of light emitting nanometer-thick films.In this contribution, we present an alternative approach for the development of europium-based nanofilms, departing from conventional doping methods that rely on host matrices, typically oxides and oxinitrides of diverse elements, to encapsulate the Eu2+ or Eu3+ emitter ions [4-6]. We highlight the efficacy of employing direct Eu compounds, maximizing the number of active emitters in the nanofilms and resulting in the observation of intense emission from these nanostructures. Our search started with original studies on Eu oxides (EuOx 1/3<x<1), and demonstrated a broad tuning of their emission by controlling their stoichiometry [1]. In this context, we present the progress achieved through the successful fabrication of europium oxyhydroxide (EuOOH) nanofilms [7]. It is noteworthy that the conventional method for producing hydroxides and oxyhydroxides involves chemical hydrothermal procedures with multiple steps, including dehydration, ultimately yielding powders and micro-crystals unsuitable for integration. In contrast, our methodology employs a clean physical evaporation technique under vacuum conditions, yielding thin films ready for integration. Crystalline monoclinic EuOOH nanofilms were successfully grown on silicon substrates by using pulsed laser deposition (PLD) and a subsequent annealing at a low temperature (250ºC). We will provide evidence of the physical mechanisms governing OH incorporation and discuss the influence of oxygen (O) and hydroxyl (OH) content on the resulting red emission of the Eu3+ ions related to the 5D0→2FJ transition, and on the optical properties of the films through the visible and infrared spectrum.[1] A. Mariscal-Jiménez et al, J. Phys. Chem. C 2020, 124, 15434.[2] P. Gomez-Rodriguez, et al, Nanophotonics 2021, 16, 3995-4007.[3] T. Zhong and P. Goldner, Nanophotonics 2019, 8, 2015.[4] D. Jaque and F. Vetrone, Nanoscale 2012, 4, 4301.[5] I. Camps, A. Mariscal-Jiménez, and R. Serna, Appl. Surf. Sci. 2023, 613, 1.[6] C. W. Bond et al. Opt. Mater. 2021, 122, 111796.[7] A. Caño, B. Galiana, G. B. Perea, J. Gonzalo and R. Serna, Appl. Surf. Sci. 2023, 640, 158236.

Highly Confined Hybridized Polaritons in Scalable van der Waals Heterostructure Resonators.

The optimization of nanoscale optical devices and structures will enable the exquisite control of planar optical fields. Polariton manipulation is the primary strategy in play. In two-dimensional heterostructures, the ability to excite mixed optical modes offers an additional control in device design. Phonon polaritons in hexagonal boron nitride have been a common system explored for the control of near-infrared radiation. Their hybridization with graphene plasmons makes these mixed phonon polariton modes in hexagonal boron nitride more appealing in terms of enabling active control of electrodynamic properties with a reduction of propagation losses. Optical resonators can be added to confine these hybridized plasmon-phonon polaritons deeply into the subwavelength regime, with these structures featuring high quality factors. Here, we show a scalable approach for the design and fabrication of heterostructure nanodisc resonators patterned in chemical vapor deposition-grown monolayer graphene and h-BN sheets. Real-space mid-infrared nanoimaging reveals the nature of hybridized polaritons in the heterostructures. We simulate and experimentally demonstrate localized hybridized polariton modes in heterostructure nanodisc resonators and demonstrate that those nanodiscs can collectively couple to the waveguide. High quality factors for the nanodiscs are measured with nanoscale Fourier transform infrared spectroscopy. Our results offer practical strategies to realize scalable nanophotonic devices utilizing low-loss hybridized polaritons for applications such as on-chip optical components.

Deterministic quasi-continuous tuning of phase-change material integrated on a high-volume 300-mm silicon photonics platform

Programmable photonic integrated circuits (PICs) consisting of reconfigurable on-chip optical components have been creating new paradigms in various applications, such as integrated spectroscopy, multi-purpose microwave photonics, and optical information processing. Among many reconfiguration mechanisms, non-volatile chalcogenide phase-change materials (PCMs) exhibit a promising approach to the future very-large-scale programmable PICs, thanks to their zero static power and large optical index modulation, leading to extremely low energy consumption and ultra-compact footprints. However, the scalability of the current PCM-based programmable PICs is still limited since they are not directly off-the-shelf in commercial photonic foundries now. Here, we demonstrate a scalable platform harnessing the mature and reliable 300 mm silicon photonic fab, assisted by an in-house wide-bandgap PCM (Sb2S3) integration process. We show various non-volatile programmable devices, including micro-ring resonators, Mach-Zehnder interferometers and asymmetric directional couplers, with low loss (~0.0044 dB/µm), large phase shift (~0.012 π/µm) and high endurance (>5000 switching events with little performance degradation). Moreover, we showcase this platform’s capability of handling relatively complex structures such as multiple PIN diode heaters in devices, each independently controlling an Sb2S3 segment. By reliably setting the Sb2S3 segments to fully amorphous or crystalline state, we achieved deterministic multilevel operation. An asymmetric directional coupler with two unequal-length Sb2S3 segments showed the capability of four-level switching, beyond cross-and-bar binary states. We further showed unbalanced Mach-Zehnder interferometers with equal-length and unequal-length Sb2S3 segments, exhibiting reversible switching and a maximum of 5 (N+1,N=4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$N+1,N=4$$\\end{document}) and 8 (2N,N=3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${2}^{N},N=3$$\\end{document}) equally spaced operation levels, respectively. This work lays the foundation for future programmable very-large-scale PICs with deterministic programmability.

Quantum random number generation using an on-chip nanowire plasmonic waveguide

Quantum random number generators employ the inherent randomness of quantum mechanics to generate truly unpredictable random numbers, which are essential in cryptographic applications. While a great variety of quantum random number generators have been realized using photonics, few exploit the high-field confinement offered by plasmonics, which enables device footprints an order of magnitude smaller in size. Here we integrate an on-chip nanowire plasmonic waveguide into an optical time-of-arrival based quantum random number generation setup. Despite loss, we achieve a random number generation rate of 14.4Mbitss−1 using low light intensity, with the generated bits passing industry standard tests without post-processing. By increasing the light intensity, we were then able to increase the generation rate to 41.4Mbitss−1 , with the resulting bits only requiring a shuffle to pass all tests. This is an order of magnitude increase in the generation rate and decrease in the device size compared to previous work. Our experiment demonstrates the successful integration of an on-chip nanoscale plasmonic component into a quantum random number generation setup. This may lead to new opportunities in compact and scalable quantum random number generation.

Fully integrated and broadband Si-rich silicon nitride wavelength converter based on Bragg scattering intermodal four-wave mixing

Intermodal four-wave mixing (FWM) processes have recently attracted significant interest for all-optical signal processing applications thanks to the possibility to control the propagation properties of waves exciting distinct spatial modes of the same waveguide. This allows, in principle, to place signals in different spectral regions and satisfy the phase matching condition over considerably larger bandwidths compared to intramodal processes. However, the demonstrations reported so far have shown a limited bandwidth and suffered from the lack of on-chip components designed for broadband manipulation of different modes. We demonstrate here a silicon-rich silicon nitride wavelength converter based on Bragg scattering intermodal FWM, which integrates mode conversion, multiplexing and de-multiplexing functionalities on-chip. The system enables wavelength conversion between pump waves and a signal located in different telecommunication bands (separated by 60 nm) with a 3 dB bandwidth exceeding 70 nm, which represents, to our knowledge, the widest bandwidth ever achieved in an intermodal FWM-based system.

Microwire-based multifunctional microsensors for high-performance humidity and strain sensing

In this post-Moore era, on-chip components have transitioned into the “more Moore” and “more than Moore” technology routes. Serving as the foundational point and data source for all intelligent devices, sensors are undergoing development for multifunctionality, systematization, and integration. However, the current micro/nano multifunctional sensor fabrication technology is not sufficiently advanced to meet the requirements of practical applications. In this study, we prepared high-precision microwire arrays as multifunctional microsensors. This microsensor exhibited a highly sensitive response to humidity and bending strain. It has a sensitivity of up to 8520% and response time as low as 0.9/3.5 s (response/recovery) over a wide range of humidity variations from 23% to 97%. In the bending strain range of −0.4–0.4%, the microsensor exhibits a gauge factor of up to 267. This multifunctional microsensor has the potential for use in integrated intelligent devices.

Coaxial Cable-Based Magnetic and Electric Near-Field Probes to Measure On-Chip Components up to 330 GHz

Coaxial Cable-Based Magnetic and Electric Near-Field Probes to Measure On-Chip Components up to 330 GHz

Multiplexing of bias-controlled modulation modes on a monolithic III-nitride optoelectronic chip.

III-nitride optoelectronic chips have tremendous potential for developing integrated computing and communication systems with low power consumption. The monolithic, top-down approaches are advantageous for simplifying the fabrication process and reducing the corresponding manufacturing cost. Herein, an ultraviolet optical interconnection system is investigated to discover the way of multiplexing between emission and absorption modulations on a monolithic optoelectronic chip. All on-chip components, the transmitter, monitor, waveguide, modulator, and receiver, share the same quantum well structure. As an example, two bias-controlled modulation modes are used to modulate video and audio signals in the experiment presented in this Letter. The results show that our on-chip optoelectronic system works efficiently in the near ultraviolet band, revealing the potential breadth of GaN optoelectronic integration.

Thermal Transport in Nanoelectronic Devices Cooled by On-Chip Magnetic Refrigeration.

On-chip demagnetization refrigeration has recently emerged as a powerful tool for reaching microkelvin electron temperatures in nanoscale structures. The relative importance of cooling on-chip and off-chip components and the thermal subsystem dynamics are yet to be analyzed. We study a Coulomb blockade thermometer with on-chip copper refrigerant both experimentally and numerically, showing that dynamics in this device are captured by a first-principles model. Our work shows how to simulate thermal dynamics in devices down to microkelvin temperatures, and outlines a recipe for a low-investment platform for quantum technologies and fundamental nanoscience in this novel temperature range.

Design and analysis of on-chip reconfigurable photonic components for photonic multiply and accumulate operation

Design and analysis of on-chip reconfigurable photonic components for photonic multiply and accumulate operation

Adaptive Image Size Padding for Load Balancing in System-on-Chip Memory Hierarchy

The conventional address map often incurs traffic congestion in on-chip memory components and degrades memory utilization when the access pattern of an application is not matched with the address map. To reduce traffic congestion and improve the memory system performance, we propose an adaptive image size padding technique for a given address mapping and a hardware configuration. In the presented software approach, the system can adaptively determine the image pad size at the application-invoke time to enhance the load balancing across the on-chip memory hierarchy. Mainly targeting a high-bandwidth image processing application running in a device accelerator of an embedded system, we present the design, describe the algorithm, and conduct the performance experiment. As a result, the experiments indicate the presented design can improve load balancing up to 95% and performance up to 35%, with insignificant memory footprint overheads.

Telecom-band-integrated multimode photonic quantum memory.

Telecom-band-integrated quantum memory is an elementary building block for developing quantum networks compatible with fiber communication infrastructures. Toward such a network with large capacity, an integrated multimode photonic quantum memory at telecom band has yet been demonstrated. Here, we report a fiber-integrated multimode quantum storage of single photon at telecom band on a laser-written chip. The storage device is a fiber-pigtailed Er3+:LiNbO3 waveguide and allows a storage of up to 330 temporal modes of heralded single photon with 4-GHz-wide bandwidth at 1532 nm and a 167-fold increasing of coincidence detection rate with respect to single mode. Our memory system with all-fiber addressing is performed using telecom-band fiber-integrated and on-chip components. The results represent an important step for the future quantum networks using integrated photonics devices.

Giant Nonlinear Optical Response via Coherent Stacking ofIn-Plane Ferroelectric Layers.

Thin ferroelectric materials hold great promise for compact nonvolatile memory and nonlinear optical and optoelectronic devices. Herein, an ultrathin in-plane ferroelectric material that exhibits a giant nonlinear optical effect, group-IV monochalcogenide SnSe, is reported. Nanometer-scale ferroelectric domains with ≈90°/270° twin boundaries or ≈180° domain walls are revealed in physical-vapor-deposited SnSe by lateral piezoresponse force microscopy. Atomic structure characterization reveals both parallel and antiparallel stacking of neighboring van der Waals ferroelectric layers, leading to ferroelectric or antiferroelectric ordering. Ferroelectric domains exhibit giant nonlinear optical activity due to coherent enhancement of second-harmonic fields and the as-resulted second-harmonic generationwasobserved to be 100 times more intense than monolayer WS2 . This work demonstratesin-plane ferroelectric ordering and giant nonlinear optical activity in SnSe, which paves the way for applications in on-chip nonlinear optical components and nonvolatile memory devices.

Optimization of heterogeneously integrated InP-Si on-chip photonic components.

We demonstrate comprehensive numerical studies on a hybrid III-V/Si-based waveguide system, serving as a platform for efficient light coupling between an integrated III-V quantum dot emitter to an on-chip quantum photonic integrated circuit defined on a silicon substrate. We propose a platform consisting of a hybrid InP/Si waveguide and an InP-embedded InAs quantum dot, emitting at the telecom C-band near 1550 nm. The platform can be fabricated using existing semiconductor processing technologies. Our numerical studies reveal nearly 87% of the optical field transfer efficiency between geometrically-optimized InP/Si and Si waveguides, considering propagating field along a tapered geometry. The coupling efficiency of a directional dipole emission to the hybrid InP/Si waveguide is evaluated to ∼38%, which results in more than 33% of the total on-chip optical field transfer efficiency from the dipole to the Si waveguide. We also consider the off-chip outcoupling efficiency of the propagating photon field along the Si waveguide by examining the normal to the chip plane and in-plane outcoupling configurations. In the former case, the outcoupling amounts to ∼26% when using the circular Bragg grating outcoupler design. In the latter case, the efficiency reaches up to 8%. Finally, we conclude that the conceptual device's performance is weakly susceptible to the transferred photon wavelength, offering a broadband operation within the 1.5-1.6 µm spectral range.

Terahertz waveform synthesis in integrated thin-film lithium niobate platform

Bridging the “terahertz gap“ relies upon synthesizing arbitrary waveforms in the terahertz domain enabling applications that require both narrow band sources for sensing and few-cycle drives for classical and quantum objects. However, realization of custom-tailored waveforms needed for these applications is currently hindered due to limited flexibility for optical rectification of femtosecond pulses in bulk crystals. Here, we experimentally demonstrate that thin-film lithium niobate circuits provide a versatile solution for such waveform synthesis by combining the merits of complex integrated architectures, low-loss distribution of pump pulses on-chip, and an efficient optical rectification. Our distributed pulse phase-matching scheme grants shaping the temporal, spectral, phase, amplitude, and farfield characteristics of the emitted terahertz field through designer on-chip components. This strictly circumvents prior limitations caused by the phase-delay mismatch in conventional systems and relaxes the requirement for cumbersome spectral pre-engineering of the pumping light. We propose a toolbox of basic blocks that produce broadband emission up to 680 GHz and far-field amplitudes of a few V m−1 with adaptable phase and coherence properties by using near-infrared pump pulse energies below 100 pJ.

Topological disclination states for surface acoustic waves

Surface acoustic waves (SAWs) are widely involved in today's communication and sensing networks. Recent exploration of topological SAWs has provided promising prospects for developing future hybrid SAW devices. In this paper, by designing tight-binding phononic crystals on a semi-infinite substrate, we revealed topological disclination states, i.e., a kind of bound state in topologically condensed matters, for the SAWs. Numerical simulations show that the bound states induced by disclination in the SAW system are more diverse than in previous electromagnetic and mechanical systems. SAW resonances in the disclinations can be efficiently excited by appropriate mechanical stimulation with decent qualities. These states are robust and flexible for design, providing options for future multifunctional and interdisciplinary SAW manipulators, processors, sensors, and other on-chip integrated components.

Iron Oxide Nanoparticle-Based Ferro-Nanofluids for Advanced Technological Applications.

Iron oxide nanoparticle (ION)-based ferro-nanofluids (FNs) have been used for different technological applications owing to their excellent magneto-rheological properties. A comprehensive overview of the current advancement of FNs based on IONs for various engineering applications is unquestionably necessary. Hence, in this review article, various important advanced technological applications of ION-based FNs concerning different engineering fields are critically summarized. The chemical engineering applications are mainly focused on mass transfer processes. Similarly, the electrical and electronics engineering applications are mainly focused on magnetic field sensors, FN-based temperature sensors and tilt sensors, microelectromechanical systems (MEMS) and on-chip components, actuators, and cooling for electronic devices and photovoltaic thermal systems. On the other hand, environmental engineering applications encompass water and air purification. Moreover, mechanical engineering or magneto-rheological applications include dampers and sealings. This review article provides up-to-date information related to the technological advancements and emerging trends in ION-based FN research concerning various engineering fields, as well as discusses the challenges and future perspectives.

Crosstalk Reduction between Closely Spaced Optical Waveguides by Using Higher-Order Modes

Optical waveguide structures can make the state-of-the-art micro- and nanofabricated devices faster and less energy consuming. However, on-chip optical components must be placed at relatively large distances from each other, on the order of the wavelength $\ensuremath{\lambda}$, to eliminate the crosstalk between them. This makes on-chip optical structures too large to compete with their electronic counterparts. In this work, we explore the possibility of suppressing the crosstalk between closely spaced dielectric waveguides by making use of higher-order modes. We show that the crosstalk between two waveguides can be essentially eliminated, even if the waveguides are separated by a distance of $\ensuremath{\lambda}/10$ only. We also study arrays of more than two waveguides and find the conditions for the efficient crosstalk reduction in them. Our results can lead to further miniaturization of photonic integrated circuits.