XiO Photonics (Netherlands)

Aquaculture is expected to play a vital role in solving the challenge of sustainably providing the growing world population with healthy and nutritious food. Pathogen outbreaks are a major risk for the sector, so early detection and a timely response are crucial. This can be enabled by monitoring the pathogen levels in aquaculture facilities. This paper describes a photonic biosensing platform based on silicon nitride waveguide technology with integrated active components, which could be used for such applications. Compared to the state of the art, the current system presents improvements in terms of miniaturization of the Photonic Integrated Circuit (PIC) and the development of wafer-level processes for hybrid integration of active components and for material-selective chemical and biological surface modification. Furthermore, scalable processes for integrating the PIC in a microfluidic cartridge were developed, as well as a prototype desktop readout instrument. Three bacterial aquaculture pathogens (Aeromonas salmonicida, Vagococcus salmoninarum, and Yersinia ruckeri) were selected for assay development. DNA biomarkers were identified, corresponding primer-probe sets designed, and qPCR assays developed. The biomarker for Aeromonas was also detected using the hybrid PIC platform. This is the first successful demonstration of biosensing on the hybrid PIC platform.

Truly portable supercontinuum sources with high spectral bandwidths are poised to advance applications such as medical imaging, chemical sensing, or light detection and ranging. Yet, limited efficiencies of conventional Supercontinuum Generation (SCG) schemes typically require relatively high pulse energies from bulky ultrafast lasers. We discuss a commercially emerging approach to SCG based on Patterned Sign-alternating Dispersion (PSD) waveguide chips. It is based on alternately subjecting femtosecond seed laser pulses to normal and anomalous dispersion regimes in a highly controlled fashion. PSD waveguides decrease input power requirements down to factors on the order of 1/1000 as compared to other approaches and imply a disruptive reduction in power consumption, size, and costs of required seed laser light sources. We illustrate the real-world performance of PSD waveguide chips operating in tandem with ultra-compact femtosecond fiber lasers, and give an illustrative example of portable near-infrared absorption spectroscopy.

Over the past two decades, the fast development of superconducting nanowire single photon detector (SNSPD) has made them the detector of choice for modern stringent quantum optics experiments. SNSPD offers remarkably high efficiencies, approching unity efficiency, a few pico-second time resolution, and gigahertz counting rates. The recovery time <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\tau$</tex> of the SNSPD is one of the key parameters influencing its efficiency at high photon fluxes. Here we report on preliminary results of controlling the response speed of the SNSPD by introducing a tunable resistor <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$R_{S}$</tex> in the electric circuit.

The high rate of drug withdrawal from the market due to cardiovascular toxicity or lack of efficacy, the economic burden, and extremely long time before a compound reaches the market, have increased the relevance of human in vitro models like human (patient-derived) pluripotent stem cell (hPSC)-derived engineered heart tissues (EHTs) for the evaluation of the efficacy and toxicity of compounds at the early phase in the drug development pipeline. Consequently, the EHT contractile properties are highly relevant parameters for the analysis of cardiotoxicity, disease phenotype, and longitudinal measurements of cardiac function over time. In this study, we developed and validated the software HAARTA (Highly Accurate, Automatic and Robust Tracking Algorithm), which automatically analyzes contractile properties of EHTs by segmenting and tracking brightfield videos, using deep learning and template matching with sub-pixel precision. We demonstrate the robustness, accuracy, and computational efficiency of the software by comparing it to the state-of-the-art method (MUSCLEMOTION), and by testing it with a data set of EHTs from three different hPSC lines. HAARTA will facilitate standardized analysis of contractile properties of EHTs, which will be beneficial for in vitro drug screening and longitudinal measurements of cardiac function.

Hybrid integrated diode lasers offer a robust and small-sized solution for applications in telecommunications, quantum optics and metrology due to their wide tunability and ultra-narrow linewidth. Here, we present the fabrication, packaging and successful operation of the first fully integrated, aluminum oxide (Al2O3) based, hybrid diode laser operating at 405 nm. Low-loss, high-confinement waveguides are fabricated with a measured propagation loss of only 2.8 ± 0.3 dB/cm. The hybrid laser consists of a GaN SLED butt-coupled to an Al2O3 feedback circuit comprising of two microring resonators that form a frequency selective Vernier filter. The chip assembly is packaged in a hermetically sealed, butterfly housing for optimal performance and durability. The laser shows a maximum output power of 0.74 mW and is tunable over the entire gain bandwidth of 4.4 nm.

.SignificanceInterstitial fiber-based spectroscopy is gaining interest for real-time in vivo optical biopsies, endoscopic interventions, and local monitoring of therapy. Different from other photonics approaches, time-domain diffuse optical spectroscopy (TD-DOS) can probe the tissue at a few cm distance from the fiber tip and disentangle absorption from the scattering properties. Nevertheless, the signal detected at a short distance from the source is strongly dominated by the photons arriving early at the detector, thus hampering the possibility of resolving late photons, which are rich in information about depth and absorption.AimTo fully benefit from the null-distance approach, a detector with an extremely high dynamic range is required to effectively collect the late photons; the goal of our paper is to test its feasibility to perform TD-DOS measurements at null source–detector separations (NSDS).ApproachIn particular, we demonstrate the use of a superconducting nanowire single photon detector (SNSPD) to perform TD-DOS at almost NSDS by exploiting the high dynamic range and temporal resolution of the SNSPD to extract late arriving, deep-traveling photons from the burst of early photons.ResultsThis approach was demonstrated both on Monte Carlo simulations and on phantom measurements, achieving an accuracy in the retrieval of the water spectrum of better than 15%, spanning almost two decades of absorption change in the 700- to 1100-nm range. Additionally, we show that, for interstitial measurements at null source–detector distance, the scattering coefficient has a negligible effect on late photons, easing the retrieval of the absorption coefficient.ConclusionsUtilizing the SNSPD, broadband TD-DOS measurements were performed to successfully retrieve the absorption spectra of the liquid phantoms. Although the SNSPD has certain drawbacks for use in a clinical system, it is an emerging field with research progressing rapidly, and this makes the SNSPD a viable option and a good solution for future research in needle guided time-domain interstitial fiber spectroscopy.

A superconducting nanowire single-photon detector was utilized to enable fast time-domain diffuse correlation spectroscopy to measure cerebral blood flow in adult brain separating early and late photons.

In this paper, we investigated the realization of Lab on fiber accelerometers based on micro-opto-mechanical cavities on the optical fiber tip. Two alternative approaches have been pursued. In the former one, the opto-mechanical cavity includes a simple cantilever suspended on the optical fiber end facet. In the latter, the opto-mechanical structure consists of a membrane sustained by four cantilevers. The mechanical response of the sensors has been predicted by numerical simulations based on the finite element method. Cantilever based accelerometers have been realized by using a ferrule top approach, whilst membrane based accelerometers have been realized through a photolithographic process followed by a transferring step for the final integration on the optical fiber tip. Different accelerometers have been fabricated with different geometrical features and characterized by using a shaking table. Either cantilever and membrane based Lab on fiber accelerometers exhibited a sensitivity of about 0.1 nm/(m/s2) on a 3 dB-bandwidth of 5 kHz with a resolution down to 100 μg/(Hz)1/2. Overall, the performance comparison with the actual state of the art confirms the potentiality and the versatility underlying the integration of micro-opto-mechanical (MOM) structures with the optical fibers towards a novel class of opto-mechanical lab on fiber accelerometers.

Hybrid OFDM-digital filter multiple access (OFDM-DFMA) PONs exploit software configurable digital shaping filters in ONUs to multiplex multiple gapless OFDM channels at different radio frequencies and utilize a single FFT operation-based pipelined DSP procedure in the OLT to simultaneously de-multiplex/demodulate all OFDM signals from various ONUs without requiring any digital matching filters. In this letter, aggregated raw 30Gbit/s over 25km multipoint-to-point upstream signal transmissions of IMDD OFDM-DFMA PONs are experimentally demonstrated for the first time. Experimental results show that a reduction in ONU-embedded digital filter length from 256 to 16 just decreases the receiver sensitivity by $L=16$ , fibre transmission impairments (channel interference) are shown to give 3.5dB (>5.5 dB) ONU launch power dynamic range is also achievable for an aggregated upstream transmission raw capacity of 28.12Gbit/s (23.43Gbit/s).

Future quantum optical networks will require an integrated solution to multiplex suitable sources and detectors on a low-loss platform. Here we combined superconducting single-photon detectors with colloidal PbS/CdS quantum dots (QDs) and low-loss silicon nitride passive photonic components to show their combined operation at cryogenic temperatures. Using a planar concave grating spectrometer, we performed wavelength-resolved measurements of the photoluminescence decay of QDs, which were deterministically placed in the gap of plasmonic antennas, in order to improve their emission rate. We observed a Purcell enhancement matching the antenna simulations, with a concurrent increase of the count rate on the superconducting detectors.