16 research outputs found
Φωτονικά ολοκληρωμένα κυκλώματα για υλοποίηση οπτικών στοιχειοκεραιών και εφαρμογές τηλεπισκόπισης με ετερώδυνη ανίχνευση
No full textPhotonic integration is a powerful technology for miniaturizing optical devices and systems. Being in the center of research interest for over two decades, photonic integration has made tremendous progress, driven primarily by the information industry's demand for high-bandwidth optical interconnects. However, its maturation has opened the door to new applications in recent years. Remote sensing and ranging applications have gained significant momentum as the next potential mass-market opportunity for photonic integrated circuits (PICs), particularly due to the automotive industry's growing interest in LiDAR. Many different technologies have spawn to address challenges related to high accuracy sensing and fast scanning and develop scalable and cost-effective solutions.Among the various existing integration platforms, silicon nitride (SiN) and polymer-based photonic integration are particularly interesting for remote sensing applications, primarily due to their low loss waveguides and passive components, their wide spectral range of operation, and the high-optical-power handling capabilities. This work leverages these platforms to develop two novel functionalities: optical frequency shifting (OFS) for heterodyne interferometry and two-dimensional laser-beam steering based on optical phased arrays (OPAs). OFS is based on stress-optic index modulation, that offers larger bandwidth than conventional thermo-optic phase shifters, by using lead zirconate titanate (PZT) thin films deposited on top of the SiN waveguides with a wafer-scale process. The OFS PICs are integrated into a NIR laser Doppler vibrometer (LDV) system for non-contact measurements of a vibrating surface. Furthermore, a process for hybrid integration of polymer waveguides on top of the SiN platform is introduced, to combine functionalities from both platforms in a fully compact manner. Optical phased arrays (OPAs) are implemented in the polymer-based technology platform, where multiple waveguiding layers are used to form rectangular apertures at the edge facet of the PICs. Two-dimensional (2D) steering of a NIR laser beam is demonstrated by individual phase control of each OPA channel using thermo-optic phase shifters. Linear aperiodic OPAs with non-uniform emitter spacing are explored to enhance the field of view and reduce control complexity. OPA characterization and calibration aspects are discussed, as well as fabrication considerations for multi-layer polymer PICs. Although the multi-waveguide-layer approach for 2D edge-emitting OPAs has been previously suggested, this work presents the first experimental demonstration of 2D beam steering based on this concept.Η φωτονική ολοκλήρωση βρίσκεται στο επίκεντρο της ερευνητικής δραστηριότητας για περισσότερο από δύο δεκαετίες, έχοντας σημειώσει αξιοσημείωτη πρόοδο στην κατασκευή ολοκληρωμένων οπτικών συσκευών και κυκλωμάτων, κυρίως λόγω της ανάγκης για οπτικές διασυνδέσεις υψηλού εύρους ζώνης στα δίκτυα επικοινωνιών. Ωστόσο, η ωρίμανση της τεχνολογίας έχει ανοίξει τον δρόμο σε νέες εφαρμογές τα τελευταία χρόνια. Οι εφαρμογές τηλεπισκόπησης έχουν αποκτήσει σημαντική δυναμική ως η επόμενη μεγάλη εμπορική ευκαιρία για τα φωτονικά ολοκληρωμένα κυκλώματα (PICs), κυρίως λόγω του ενδιαφέροντος της αυτοκινητοβιομηχανίας για συστήματα LiDAR. Προς αυτή την κατεύθυνση έχουν αναπτυχθεί πολλές τεχνολογίες, με στόχο την αντιμετώπιση προκλήσεων που σχετίζονται με την υψηλή ακρίβεια μέτρησης, τη γρήγορη σάρωση, καθώς και την ανάπτυξη οικονομικά αποδοτικών λύσεων κλίμακας. Μεταξύ των διάφορων τεχνολογιών ολοκλήρωσης, η πλατφόρμα ολοκλήρωσης του silicon nitride (SiN) και η ολοκλήρωση που βασίζεται σε πολυμερή, παρουσιάζουν ιδιαίτερο ενδιαφέρον για εφαρμογές τηλεπισκόπησης λόγω των χαμηλών οπτικών απωλειών, την ικανότητα διαχείρισης υψηλής οπτικής ισχύος, καθώς και του φασματικού εύρους λειτουργίας που υποστηρίζουν. Η παρούσα εργασία αξιοποιεί τις δύο παραπάνω πλατφόρμες για την ανάπτυξη δύο νέων λειτουργιών: την μετατόπιση οπτικής συχνότητας (Optical Frequency Shifting - OFS) για ετερόδυνη συμβολομετρία και τη σάρωση μίας οπτικής δέσμης laser στο χώρο με χρήση οπτικών στοιχειοκεραιών (Optical Phased Arrays - OPAs). Για την υλοποίηση κυκλωμάτων μετατόπισης της οπτικής συχνότητας χρησιμοποιούνται λεπτές στρώσεις PZT επάνω από τους κυματοδηγούς SiN για τη διαμόρφωση του δείκτη διάθλασης μέσω του πιεζο-οπτικού φαινομένου, το οποίο προσφέρει μεγαλύτερο εύρος ζώνης σε σχέση με τους συμβατικούς θερμο-οπτικούς διαμορφωτές φάσης. Τα OFS PICs ενσωματώνονται σε ένα σύστημα απομακρυσμένης μέτρησης δονήσεων Laser Doppler Vibrometer (LDV). Επιπλέον, προτείνεται μια διαδικασία υβριδικής ολοκλήρωσης πολυμερικών κυματοδηγών επάνω στην πλατφόρμα SiN για το συνδυασμό των λειτουργιών που υποστηρίζει η κάθε πλατφόρμα σε ένα τσιπ. Οι διατάξεις οπτικών στοιχειοκεραιών υλοποιούνται στην πολυμερική πλατφόρμα, στην οποία χρησιμοποιείται μία προσέγγιση κάθετης ολοκλήρωση για το σχηματισμό πολλαπλών επιπέδων κυματοδήγησης και συνεπώς δισδιάστατων OPAs στην άκρη του τσιπ. Για τη ρύθμιση της φάσης του οπτικού πεδίου σε κάθε κυματοδηγό χρησιμοποιούνται θερμο-οπτικοί διαμορφωτές φάσης χαμηλής κατανάλωσης ισχύος. Επιπλέον, μελετώνται γραμμικές διατάξεις στοιχειοκεραιών με ανομοιόμορφη κατανομή των στοιχείων, για την αύξηση του οπτικού πεδίου (FOV) και τη μείωση της πολυπλοκότητας ελέγχου. Συζητούνται θέματα χαρακτηρισμού και βαθμονόμησης των OPAs, καθώς και παράμετροι κατασκευής των πολύ-επίπεδων πολυμερικών PICs. Η παρούσα εργασία αποτελεί την πρώτη πειραματική υλοποίηση στροφής δέσμης στις δύο διαστάσεις με χρήση PIC πολλαπλών επιπέδων κυματοδήγησης
Studies on the readability and on the detection rate in a Mach–Zehnder interferometer-based implementation for high-rate, long-distance QKD protocols
No full textWe study the way that chromatic dispersion affects the visibility and the synchronization on quantum key distribution (QKD) protocols in a widely used setup based on the use of two fiber-based Mach–Zehnder interferometers at transmitter/receiver stations. We identify the necessary conditions for the path length difference between the two arms of the interferometers for achieving the desired visibility given the transmission distance, where the form of the detector’s window can be considered. We also associate the above limitations with the maximum detection rate that can be recorded in our setup, including the quantum nonlinearity phenomenon, and with the maximum time window of the detector’s gate. Exploiting our results, we provide two methods, depending on the clock rate of the setup, to perform chromatic dispersion compensation techniques to the signal for keeping the correct order of the transmitted symbols. At the end, we apply our theoretical outcomes in a more realistic QKD deployment, considering the case of phase-encoding BB84 QKD protocol, which is widely used. Our proposed methods, depending on the transmission distance and on the photon emission rate at transmitter station, can be easily generalized to every fiber-optic QKD protocol, for which the discrimination of each symbol is crucial
Design of ultra-compact multimode interference (MMI) couplers and high efficiency grating couplers in TriPleX platform as part of a photonic based sensor
No full textCoexistence of Discrete-Variable QKD with WDM Classical Signals in the C-Band for Fiber Access Environments
No full textOptical Beamforming Networks Supporting Multibeam and Multicast Operation
No full textIn this paper, we validate the intrinsic capability of optical beamforming networks (OBFNs) to support simultaneously multi-beam and multicast operations. Through simulation analyses and assuming operation in the downlink direction of a wireless system, we verify the capability of an OBFN based on Blassmatrix architecture and an OBFN based on true-time delay (TTD) elements to support this hybrid mode of operation by calculating the radiation patterns and the resultant constellation diagrams of the demodulated signals at the corresponding observation angles. Finally, we experimentally assess the performance of a 1×4 TTD-OBFN based on commercially available components in the case of multicast operation. Using microwave signals at 15 GHz carrier frequency, high order modulation formats and 1 Gbaud symbol rates, we modulate the amplitude of a single optical carrier. After the processing of the modulated signals by the OBFN, we validate its potential to support multicast operation by calculating the BER of the received signals at the corresponding observation angles as a function of the optical power at the output of the OBFN. The BER remains below 10-3 for received optical power higher than -4 dBm, validating the potential of this OBFN architecture to support multicast operation
Multi-Rate and Multi-Channel Optical Equalizer Based on Photonic Integration
No full textWe propose and experimentally demonstrate a photonic integrated circuit (PIC) that operates as an optical equalizer (OE) with multi-rate and multi-channel capability. The OE has the structure of a 3-tap direct form finite impulse response (FIR) filter and is based on the use of micro-ring resonators (MRRs) for the tuning of its delay lines. The PIC is fabricated on TriPleX platform and has 17 reconfigurable elements in total including nine MRRs, five optical couplers and three standalone phase shifters. Using this OE in an on-off keying system with bandwidth limitations we achieve an eye-diagram opening improvement more than 14 dB working with signals at 4.67 and 5.84 Gbaud both in single- and dual-channel operation. Extension to higher modulation formats is direct. Extension to higher symbol rates is also possible via the use of smaller MRRs
Portable FT-NIR spectroscopic sensor for detection of chemical precursors of explosives using advanced prediction algorithms
No full textNear-infrared (NIR) spectroscopy has acquired widespread adoption in various sectors as a result of its benefits over other analytical techniques, the most notable of which is the ability to record spectra for solid samples without any prior manipulation. Furthermore, advances in instrumentation have led to the creation of compact and high-speed spectrometers that can be used in a variety of scenarios, including hazardous materials identification. Fourier Transform NIR (FT-NIR) technology is one of the most useful tools for onsite analysis of chemical and biological substances. Herein, we propose a compact, portable FT-NIR spectroscopic sensor for field measurements, based on commercial broadband light source and spectrometer for detection of chemical precursors of explosives. We mainly focus on four compounds, ammonium nitrate, potassium nitrate, sodium nitrate and urea, some of the best-known chemical precursors of explosives with NIR content. A customized spectral library is constructed, including the forementioned substances under different environmental conditions. We emphasize on two basic factors that can affect the NIR spectra: the relative humidity and the ambient temperature. For the unknown spectrum identification, we evaluate prediction models which involve the use of Random Forest and Support Vector Machine, as well as the Hit Quality Index (HQI) value. The FT-NIR spectroscopic sensor additionally includes an integrated communication module that provides measurement spectra and results to a novel edge computing platform, called DECIoT. We demonstrate the operation of the FT-NIR spectroscopic sensor in real settings under humidity, straight sunlight, and temperature fluctuations, achieving maximum accuracy of 0.96.Copyright 2022 Society of Photo-Optical Instrumentation Engineers (SPIE). One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper/publication for a fee or for commercial purposes, and/or modification of the content of the paper/publication are prohibited
Sparse Aperiodic Optical Phased Arrays on Polymer Integration Platform
No full text469472We demonstrate solid-state optical beam-steering utilizing polymer waveguides as edge emitters to form optical phased arrays (OPAs) for operation at 1550 nm. Waveguide spacing below the wavelength is hindered in low index contrast OPAs by cross-coupling, leading to the formation of unwanted grating lobes in the far field. We employ non-uniform spacing between the 16 channels of the OPAs to suppress the grating lobes and improve the unambiguous beam steering range. Three different aperiodic layouts are fabricated and experimentally tested. Within a steering range of ±10° we achieve an average beamwidth of 0.45° with an ordered spacing layout, and 0.52° and 0.69° with a randomized spacing layout of 8lambda and 5lambda average spacing, respectively. With the latter we show suppression of the sidelobes of >11 dB and >6 dB within a steering range of ±5° and ±8°, accordingly. Power consumption of 1.28 mW/pi per channel is achieved thanks to the excellent thermo-optic (TO) coefficient of the polymer platform. To the best of our knowledge, we are the first to demonstrate polymer-based OPAs with aperiodic spacing.36
