We report on the upgrade of the fiber link of FIES, the high-resolution echelle spectrograph at the Nordic Optical Telescope (NOT). In order to improve the radial velocity (RV) stability of FIES, we replaced the circular fibers by octagonal and rectangular ones to utilize their superior scrambling performance. Two additional fibers for a planned polarimetry mode were added during the upgrade. The injection optics and the telescope front-end were also replaced. The first on-sky RV measurements indicate that the influence of guiding errors is greatly suppressed, and the overall RV precision of FIES has significantly improved.
In this work, we present a study on photonic biosensors based on Si<sub>3</sub>N<sub>4</sub> asymmetric Mach-Zehnder Interferometers (aMZI) for Aﬂatoxin M1 (AFM1) detection. AFM1 is an hepatotoxic and a carcinogenic toxin present in milk. The biosensor is based on an array of four Si<sub>3</sub>N<sub>4</sub> aMZI that are optimized for 850nm wavelength. We measure the bulk Sensitivity (S) and the Limit of Detection (LOD) of our devices. In the array, three devices are exposed and have very similar sensitivities. The fourth aMZI, which is covered by SiO<sub>2</sub>, is used as an internal reference for laser (a VCSEL) and temperature ﬂuctuations. We measured a phase sensitivity of 14300±400 rad/RIU. To characterize the LOD of the sensors, we measure the uncertainty of the experimental readout system. From the measurements on three aMZI, we observe the same value of LOD, which is ≈ 4.5×10<sup>−7</sup> RIU. After the sensor characterization on homogeneous sensing, we test the surface sensing performances by ﬂowing speciﬁc Aﬂatoxin M1 and non-speciﬁc Ochratoxin in 50 mM MES pH 6.6 buﬀer on the top of the sensors functionalized with Antigen-Recognising Fragments (Fab’). The diﬀerence between speciﬁc and non-speciﬁc signals shows the speciﬁcity of our sensors. A moderate regeneration of the sensors is obtained by using glycine solution.
In this paper we demonstrate design, fabrication and characterization of polycrystalline silicon (poly-Si) photodetectors monolithically integrated on top of a silicon oxynitride (SiON) passive photonic circuit. The devices are developed for operation at the wavelength of ~850nm. Interdigitated PIN structures were designed and compared with conventional lateral PIN detectors. The devices, fabricated in standard CMOS technology, exhibit low dark current values of few nanoamperes. The best responsivity of 0.33A/W under a reverse bias of 9V was achieved for lateral PIN detectors with 3-μm interelectrode gap, coupled vertically to the optical waveguide. The applicability of devices for lab-on-chip biosensing has been proved by demonstrating the possibility to reproduce the sensor's spectral response.
The convergence of photonics and microelectronics within a single chip is still lacking of a monolithical on-chip optical
amplifier. Rare-earth doped slot waveguides show a large potential as on-chip source. Slot waveguides with silicon
nanocrystals embedded in a dielectric host matrix can increase the light confinement in the active layer and allow
electrical injection. In this work, horizontal slot waveguides formed by two thick silicon layers separated by a thin
erbium doped silicon rich silicon oxide layer are studied as on-chip optical amplifiers. The waveguides are grown in a
CMOS line with the active material grown by low-pressure chemical vapor deposition. Optical tests are performed and
light propagation in the slot waveguides is observed. Using the cut-back technique, spectra propagation losses are
evaluated. Room temperature electroluminescence is observed at 1.54 μm. Transmitted optical signal resonant with Er
absorption is studied as a function of the injected current for different probing laser wavelengths.