We demonstrate a Brillouin-assisted low-noise photonic stepped-frequency radar system that breaks the trade-off between high signal fidelity and system simplicity, paving the way for practical, cost-effective deployment.

We demonstrate a heterogeneous lithium niobate–chalcogenide platform fabricated by shadow-mask deposition. This platform combines efficient electro-optic modulation with strong Brillouin gain for compact, integrated microwave signal processing.

We demonstrate strong Brillouin dynamic gratings (BDG) with reflectivity up to 6.5% in 3-40 cm As 2 S 3 –Ge:SiO 2 waveguides. We observe an inverse relationship between grating bandwidth and length, obeying an exponential grating strength profile, as fitted by coupled-mode modelling.

Stimulated Brillouin Scattering (SBS) is a nonlinear interaction between optical and acoustic waves in solids. First regarded as a parasitic process in optical fibers, it has gathered significant interest in microwave photonic applications such as optical signal processing and narrow linewidth lasers. While many Brillouin system demonstrations have been done on photonic chips, they struggle to provide simultaneous high Brillouin gain and narrow linewidth in a scalable platform, capable of integration with established photonic integrated circuits. Here, we present a novel integrated InGaP-on-SiO_2 platform, where a single crystalline InGaP waveguide layer offers superior material properties and strong nonlinearities to support SBS near 1550 nm wavelength. We demonstrate backward SBS with a measured high Brillouin gain coefficient of 588 W^-1 m^-1 and a record narrow linewidth of 5.2 MHz at 9.346 GHz frequency shift. This work establishes a wafer-scale complementary metal-oxide semiconductor compatible fabrication process, paving a scalable path for high gain and narrow linewidth Brillouin photonics with applications such as precision signal processing.

We demonstrate the merits of using a neuromorphic, or event-based camera (EBC), for tracking of both passive and active matter. For passive matter, we tracked the Brownian motion of different micro-particles and estimated their diffusion coefficient. For active matter, we explored the case of tracking murine spermatozoa and extracted motility parameters from the motion of cells. This has applications in enhancing outcomes for clinical fertility treatments. Using the EBC, we obtain results equivalent to those from an sCMOS camera, yet achieve a reduction in file size of up to two orders of magnitude. This is important in the modern computer era, as it reduces data throughput, and is well-aligned with edge-computing applications. We believe the EBC is an excellent choice, particularly for long-term studies of active matter.

Ultra-silicon-rich nitride Bragg gratings provide a powerful platform for precise light manipulation in photonic chips. Their exceptionally high nonlinearity and strong grating-induced dispersion near the stop-band edges significantly reduce the power and length required for chip-scale light–matter interactions. Using computational methods, we theoretically investigate modulational instability, Fermi–Pasta–Ulam recurrence, and pattern formation in this platform within the framework of the Akhmediev breather. We assess their experimental feasibility and show that this platform can generate a high-quality pulse train at the output. We demonstrate that modulational instability can be triggered in the gratings as short as 1–2 mm, leading to Akhmediev breather formation. By analyzing the full dispersion profile, we identify pump wavelengths that generate new frequencies and show that the grating also can produce a comb-like discrete spectrum. Furthermore, we reveal that even with high loss, parametric amplification at the grating output is possible, highlighting its potential as a nonlinear platform for frequency comb generation, wavelength-multiplexed data transmission, and high-precision pulse processing.

Wearable biosensors are gaining significant attention for their ability to monitor vital health signs remotely, continuously, and non-invasively. Nanomaterials offer transformative potential for next-generation soft wearable sensors, enabling seamless skin integration with enhanced comfort and data accuracy. Wet chemistry provides a scalable, cost-effective approach to producing nanomaterials, transforming rigid sensors into soft, flexible, and stretchable devices for broader wearable applications. This review highlights recent advances in soft wearable biosensors based on wet chemically produced nanomaterials, including metals, carbons, conducting polymers, conductive hydrogels, and liquid metals. It discusses fabrication techniques such as conductive ink formulation, ink delivery, electroless coating, and fiber integration, along with applications in physiological, physical, and biochemical monitoring. The review concludes by addressing challenges and opportunities, emphasizing the potential of these sensors in revolutionizing medical technology and personalized healthcare.

We numerically investigate the Cherenkov radiation in ultra-silicon-rich nitride Bragg gratings, revealing that only specific regions of the dispersion profile at the stopband edge led to radiation, while others do not.

Stimulated Brillouin scattering (SBS) offers optically tunable, narrowband gain and loss resonances, which makes it ideal for optical filtering and signal processing applications. However, broadband filters utilizing Brillouin scattering typically necessitate multiple pump sources or linear frequency modulated waveforms, which necessitate the use of overall high pump powers to achieve broadband and multi-band filter configurations. To overcome the trade-off between bandwidth and power consumption, we introduce an on-chip broadband bandpass filter scheme leveraging the SBS response and the concept of radio frequency interference. We present the MHz to GHz reconfigurable microwave photonic filters on a chip. The bandwidth is tunable from 30 MHz to 1.2 GHz at a total pump power of only 15 dBm, corresponding to a figure of merit (maximum bandwidth/pump power) improvement of a factor of 25 compared to previously reported work. Furthermore, the filter exhibits frequency tuning capabilities ranging from 10 to 40 GHz (X to Ka-band) and can be configured from single- to multi-bandpass filter responses and switched from bandpass to bandstop.

We experimentally demonstrate stimulated Brillouin scattering from surface acoustic waves (SAWs) in GeAsSe waveguides on a chip. Our modeling shows that two different SAWs are involved in the scattering process, a fundamental and higher-order SAW.

We investigate stimulated Brillouin scattering (SBS) in As2S3 waveguides over a temperature range from 18°C to 145°C. With increasing temperature, the Brillouin shift decreases at −0.55 MHz/K, while the gain coefficient decreases and gain linewidth increases without added waveguide loss. © 2024 The Author(s)

We propose and demonstrate the linearization of a Dual-Parallel Mach-Zehnder Modulator by frequency-selectively controlling the phase and amplitude of the carrier utilizing a dual-pump, narrowband on-chip Stimulated Brillouin Scattering scheme.

We inscribe a Bragg grating in an arsenic trisulfide (AS2S3) microresonator post-fabrication using material photosensitivity. The grating bandgap induces splitting of a cavity mode, which is exploited to inhibit Brillouin lasing.

Microwave photonics offers great potential for wideband systems, but link linearity remains limited and must be overcome to have the dynamic range required for many applications. Here, we propose and demonstrate the linearization of a Dual-Parallel Mach-Zehnder Modulator by frequency-selectively controlling the phase and amplitude of the carrier utilizing a dual-pump, narrowband stimulated Brillouin scattering scheme. Measurements using a single-mode fiber and chalcogenide waveguides on a chip are presented. As a result, a suppression of third-order distortion terms of 27 dB is experimentally obtained, and a spurious free dynamic range improvement of 9 dB using fiber and 4.5 dB using a chalcogenide chip, respectively. On-chip measurements enable the possibility of a fully integrated system, significantly reducing the overall footprint.

Chip-scale coherent light sources are required in applications spanning metrology and sensing to telecommunications. Brillouin lasers (BLs) offer a route to ultra-coherent optical sources in compact microresonators with free spectral range (FSR) matched to the Brillouin frequency shift (BFS). However, BFS - FSR matching typically facilitates cascaded Brillouin scattering, constraining achievable BL output power and coherence. Here, we demonstrate inhibition of cascading in a planar-integrated chalcogenide microresonator by exploiting the photonic bandgap (PBG) associated with a post-fabrication inscribed, reconfigurable intracavity Bragg grating. The PBG inhibits energy transfer within the target Brillouin scattering pathway, such as from pump to first-order Stokes wave. As a quantitative measure of Brillouin scattering inhibition, we report at least six-fold increase in threshold for onset of BL oscillation, which is ultimately limited by thermorefraction. For on-chip pump power of 399 mW, sufficient for a tenth-order Brillouin cascade, complete inhibition was achieved. Our work positions Bragg grating microresonators as an enabling platform for high performance on-chip BL sources, with reconfigurable modes of operation.

Efficient and extended light storage mechanisms are pivotal in photonics, particularly in optical communications, microwave photonics, and quantum networks, as they offer a direct route to circumvent electrical conversion losses and surmount bandwidth constraints. Stimulated Brillouin Scattering (SBS) is an established method to store optical information by transferring it to the acoustic domain, but current on-chip SBS efforts have limited bandwidth or storage time due to the phonon lifetime of several nanoseconds. An alternate approach known as quasi-light storage (QLS), which involves the creation of delayed replicas of optical data pulses via SBS in conjunction with a frequency comb, has been proposed to lift the storage time constraint; however, its realization has been confined to lengthy optical fibers, constraining integration with on-chip optical elements and form factors. Here, we present an experimental demonstration of QLS on a photonic chip leveraging the large SBS gain of chalcogenide glass, achieving delays of up to 500 ns for 1 ns long signal pulses, surpassing typical Brillouin storage processes' acoustic lifetime by more than an order of magnitude and waveguide transit time by two orders of magnitude. We experimentally and numerically investigate the dynamics of on-chip QLS and reveal that the interplay between the acoustic wave that stores the optical signal and subsequent optical pump pulses leads to a reshaping of the acoustic field. Our demonstrations illustrate the potential for achieving ultra-long storage times of individual pulses by several hundred pulse widths, marking a significant stride toward advancing the field of all-optical storage and delay mechanisms.

We demonstrate the first chip-based, GHz-class Brillouin microwave photonic filter, achieving reconfigurable RF bandwidth over 5 octaves, from 30MHz to 1.2GHz and frequency agility from 10-40GHz, with a switchable filter response between bandpass and bandstop.

In the rapidly evolving field of integrated photonics, integrated microwave photonics (MWP) stands out as a critical domain for on-chip signal processing applications. Over the past decade, harnessing stimulated Brillouin scattering (SBS) has yielded remarkable progress in this area due to its frequency tunability and unique narrowband resolution that can be achieved in a small footprint. The present article offers a comprehensive review of recent research focused on Brillouin scattering in photonic integrated circuits that guide light and sound, with a specific emphasis on heterogeneous and hybrid integration techniques tailored for applications in microwave photonics. The methodologies for realizing Brillouin hybrid circuits not only enable the seamless integration of Brillouin functions into complementary metal-oxide-semiconductor CMOS-compatible circuits but also facilitate the amalgamation of various active and passive functionalities on a single chip. Our discussion encompasses an overview of the strategies employed in harnessing Brillouin interactions, along with an examination of the associated challenges and limitations. Furthermore, we delve into both the existing and potential applications of this technology within the MWP systems domain, underscoring its multifaceted impact on contemporary research and future technological landscapes.

Signal processing based on stimulated Brillouin scattering (SBS) is limited by the narrow linewidth of the optoacoustic response, which confines many Brillouin applications to continuous wave signals or optical pulses longer than several nanoseconds. In this work, we experimentally demonstrate Brillouin interactions at the 150 ps time scale and a delay for a record 15 ns which corresponds to a delay of 100 pulse widths. This breakthrough experimental result was enabled by the high local gain of the chalcogenide waveguides as the optoacoustic interaction length reduces with pulse width. We successfully transfer 150ps-long pulses to traveling acoustic waves within a Brillouin-based memory setup. The information encoded in the optical pulses is stored for 15 ns in the acoustic field. We show the retrieval of eight amplitude levels, multiple consecutive pulses and low distortion in pulse shape. The extension of Brillouin-based storage to the ultra-short pulse regime is an important step for the realisation of practical Brillouin-based delay lines and other optical processing applications.