Vertical coupling of laser glass microspheres to buried silicon nitride ellipses and waveguides

We demonstrate the integration of Nd3+ doped Barium-Titanium-Silicate microsphere lasers with a Silicon Nitride photonic platform. Devices with two different geometrical configurations for extracting the laser light to buried waveguides have been fabricated and characterized. The first configuration relies on a standard coupling scheme, where the microspheres are placed over strip waveguides. The second is based on a buried elliptical geometry whose working principle is that of an elliptical mirror. In the latter case, the input of a strip waveguide is placed on one focus of the ellipse, while a lasing microsphere is placed on top of the other focus. The fabricated elliptical geometry (ellipticity=0.9) presents a light collecting capacity that is 50% greater than that of the standard waveguide coupling configuration and could be further improved by increasing the ellipticity. Moreover, since the dimensions of the spheres are much smaller than those of the ellipses, surface planarization is not required. On the contrary, we show that the absence of a planarization step strongly damages the microsphere lasing performance in the standard configuration.Comment: 10 pages, 4 figure

Electroluminescence efficiencies of erbium in silicon-based hosts

International audienceWe report on room-temperature 1.5 lm electroluminescence from trivalent erbium (Er3þ) ionsembedded in three different CMOS-compatible silicon-based hosts: SiO2, Si3N4, and SiNx. We showthat although the insertion of either nitrogen or excess silicon helps enhance electrical conductionand reduce the onset voltage for electroluminescence, it drastically decreases the external quantumefficiency of Er3þ ions from 2% in SiO2 to 0.001% and 0.0004% in SiNx and Si3N4, respectively.Furthermore, we present strong evidence that hot carrier injection is significantly more efficient thandefect-assisted conduction for the electrical excitation of Er3þ ions. These results suggest strategiesto optimize the engineering of on-chip electrically excited silicon-based nanophotonic light sources

Nonlinear Properties of Ge-rich Si1-xGexMaterials with Different Ge Concentrations

Silicon photonics is a large volume and large scale integration platform for applications from long-haul optical telecommunications to intra-chip interconnects. Extension to the mid-IR wavelength range is now largely investigated, mainly driven by absorption spectroscopy applications. Germanium (Ge) is particularly compelling as it has a broad transparency window up to 15 μm and a much higher third-order nonlinear coefficient than silicon which is very promising for the demonstration of efficient non-linear optics based active devices. Si1-xGexalloys have been recently studied due to their ability to fine-Tune the bandgap and refractive index. The material nonlinearities are very sensitive to any modification of the energy bands, so Si1-xGexalloys are particularly interesting for nonlinear device engineering. We report on the first third order nonlinear experimental characterization of Ge-rich Si1-xGexwaveguides, with Ge concentrations x ranging from 0.7 to 0.9. The characterization performed at 1580 nm is compared with theoretical models and a discussion about the prediction of the nonlinear properties in the mid-IR is introduced. These results will provide helpful insights to assist the design of nonlinear integrated optical based devices in both the near-and mid-IR wavelength ranges

Ge-rich graded-index Si1-xGex racetrack resonators for long-wave infrared photonics

International audienceMid-infrared racetrack resonators are demonstrated working at 8µm wavelength. The devices are based on a graded SiGe platform providing low propagation loss on a large wavelength range in the mid-IR. Different resonators designs have been fabricated, with varying gap distances in the directional coupler. Q factors of more than 3000 have been experimentally demonstrated. These results pave the way towards compact mid-IR sensors or efficient active devices

Ge-rich SiGe waveguides for supercontinuum generation in the mid-IR

International audienceThe third-order nonlinear parameter of Ge-rich SiGe waveguides are experimentally retrieved using a bi-directional top hat D-scan at λ = 1.58 µm. The obtained values are then used to fit the theoretical equation, providing promising values in the mid-IR, where the nonlinear effects are no longer limited by two-photon absorption. New Ge-rich SiGe waveguide designs are provided to exploit the nonlinear properties in the mid-IR, showing a flat anomalous dispersion over one octave spanning from λ = 3 µm to λ = 8 µm and a γ parameter that decreases from γ = 10 W-1 m-1

New fecal bacterial signature for colorectal cancer screening reduces the fecal immunochemical test false-positive rate in a screening population

Guidelines recommend routine screening for colorectal cancer (CRC) in asymptomatic adults starting at age 50. The most extensively used noninvasive test for CRC screening is the fecal immunochemical test (FIT), which has an overall sensitivity for CRC of approximately 61.0%-91.0%, which drops to 27.0%-67.0% for advanced adenomas. These figures contain a high false-positive rate and a low positive predictive value. This work aimed to develop a new, noninvasive CRC screening tool based on fecal bacterial markers capable of decreasing FIT false-positive rates in a FIT-positive population. We defined a fecal bacterial signature (RAID-CRC Screen) in a proof-of-concept with 172 FIT-positive individuals and validated the obtained results on an external cohort of 327 FIT-positive subjects. All study participants had joined the national CRC screening program. In the clinical validation of RAID-CRC Screen, a sensitivity of 83.9% and a specificity of 16.3% were obtained for the detection of advanced neoplasm lesions (advanced adenomas and/or CRC). FIT 20 μg/g produced 184 false-positive results. Using RAID-CRC Screen, this value was reduced to 154, thus reducing the false-positive rate by 16.3%. The RAID-CRC Screen test could be implemented in CRC screening programs to allow a significant reduction in the number of colonoscopies performed unnecessarily for FIT-positive participants of CRC screening programs

Mid-infrared sensing between 5.2 and 6.6 μm wavelengths using Ge-rich SiGe waveguides [Invited]

Mid-infrared (mid-IR) integrated photonics are expected to provide key advances for the demonstration of chip-scale spectroscopic systems. It has been recently reported that Ge-rich SiGe alloy-based photonic structures can provide broadband operation for a wavelength range spanning from 5.5 to 8.5 μm, thus holding great potential for mid-IR applications. In this paper, the Ge-rich SiGe platform is considered for a mid-IR photonic chip-scale sensor, based on the use of the evanescent component of the guided optical mode to probe specific molecular absorption features of the surrounding cladding environment. As a proof of concept, we monitored the absorption spectral patterns of a standalone photoresist spin-coated onto spiral Ge-rich SiGe waveguides. A significant increase of the waveguide optical loss at the spectral window of 5.8-6.2 μm is identified and correlated with the inherent photoresist absorption. The ability of this platform to sense small concentrations of methane gas is also discussed. These results pave the way towards the demonstration of compact, portable, label-free and highly sensitive photonic integrated sensors based on Ge-rich SiGe circuits

Broadband integrated racetrack ring resonators for long-wave infrared photonics

Long-wave infrared photonics is an exciting research field meant to revolutionize our daily life by means of key advances in several domains including communications, imaging systems, medical care, environmental monitoring, or multispectral chemical sensing, among others. For this purpose, integrated photonics is particularly promising owing to its compactness, mass fabrication, and energy-efficient characteristics. We present in this Letter, for the first time to the best of our knowledge, broadband integrated racetrack ring resonators operating within the crucial molecular fingerprint region. Devices show an operation bandwidth of Δλ ≈ 900 nm with a central wavelength of λ ≈ 8 μm, a quality factor of Q ≈ 3200, and an extinction ratio of ER ≈ 10 dB around the critical coupling condition. These resonant structures establish the basis of a new generation of integrated building blocks for long-wave infrared photonics that opens the route towards miniaturized multitarget molecule detection systems