Subwavelength grating waveguide devices for telecommunications applications

Subwavelength grating (SWG) waveguides in silicon-on-insulator are emerging as an enabling technology for implementing compact, high-performance photonic integrated devices and circuits for signal processing and sensing applications. We provide an overview of recent work on developing wavelength selective SWG waveguide filters based on Bragg gratings, ring resonators, and contra-directional couplers, as well as optical delay lines for applications in optical communications and microwave photonics. These components increase the SWG waveguide component toolbox and can be used to realize more complex photonic integrated circuits with enhanced or new functionalit

Silicon subwavelength grating structures for wavelength filtering applications

Photonics lies at the heart of a revolution in communications and has shown great potential in a wide range of applications from data links to biosensors, leading to the growing efforts in the development of photonic integrated circuits for optical signal processing functions. As part of this development, subwavelength grating (SWG) structures are opening more and more opportunities in the design of integrated photonic devices to contribute to the design of more complex photonic circuits. The success can be attributed to the advantages that SWG structures are able to offer; such as control over the refractive index and birefringence of optical materials without changing the standard fabrication process, which allows for the characteristics of optical devices to be optimized for specific requirements of the applications.In this thesis, we demonstrate and investigate the possibilities that SWGs offer in design of wavelength selective filters with applications in optical signal processing and microwave photonics. We firstly propose and demonstrate a novel design of contra-directional couplers (contra-DCs), in which an SWG waveguide replaces one of the asymmetric waveguides of the conventional designs. Fabricated devices on the SOI platform show over 35 dB suppression of undesired codirectional coupling and larger than 120 nm spectral range free from the interference of intrawaveguide reflections thanks to the large optical phase-mismatch between the segmented SWG waveguide and its nearby continuous waveguide. We study the effects of tailoring the period of the SWG waveguide, the gap distance between the two waveguides, and the coupling length on the spectral characteristics of the device where changing the gap distance from 100 nm up to 500 nm allows for bandwidths from 18.2 nm down to 0.9 nm. Next, we tailor the spectral characteristics of SWG-based contra-DCs. By tapering the gap distance between the SWG and strip waveguides, we demonstrate a compromise between sidelobe suppression and pass-band/stop-band extinction ratio such that the performance of the device as a potential optical add-drop multiplexer is improved. The designs with different pass-band bandwidths of 12 nm, 9 nm, and 6 nm show 10 dB to 20 dB sidelobe suppression ratio and 15 dB to 35 dB extinction ratio. We also obtain a resonant transmission peak in the stop-band of the spectral response of the device by introducing a  phase shift into the gratings of the SWG waveguide. The resonant peak has 1 nm bandwidth and 7 dB extinction ratio, where the use of the SWG waveguide in the structure of such coupler allows the characteristics of the resonant peak to be highly sensitive to the cladding material, which is of strong desire in integrated sensing applications.Finally, as wavelength division multiplexing over optical links provides an effective solution for the bandwidth challenge of off-chip and on-chip communications, we demonstrate a compact silicon photonic four-channel optical add-drop multiplexer enabled by SWG-based contra-DCs. Pass-bands of the device show on-chip insertion losses below 1.8 dB with wide 3dB bandwidth of ~6.7 nm suitable for coarse wavelength division multiplexing (CWDM) in short-reach optical interconnect applications. Transmission of 10 Gbit/s data stream through different channels of the multiplexer results in negligible power penalties while interferometric crosstalk-induced power penalties are below 2.8 dB.La photonique est au cœur d'une révolution dans les communications et a montré un grand potentiel dans une large gamme d'applications allant des liaisons de données aux biocapteurs, ce qui a conduit à des efforts croissants dans le développement de circuits intégrés photoniques pour des fonctions de traitement de signaux optiques. Dans le cadre de ce développement, les structures subwavelength grating (SWG) ouvrent de plus en plus d'opportunités dans la conception de dispositifs photoniques intégrés pour contribuer à la conception de circuits photoniques plus complexes. Le succès peut être attribué aux avantages que les structures de SWG peuvent offrir; tels que le contrôle de l'indice de réfraction et de la biréfringence des matériaux optiques sans modifier le processus de fabrication standard, ce qui permet d'optimiser les caractéristiques des dispositifs optiques pour les besoins spécifiques des applications. Dans cette thèse, nous démontrons et étudions les possibilités offertes par les SWG dans la conception de filtres sélectifs en longueur d'onde avec des applications dans le traitement du signal optique et la photonique à micro-ondes. Tout d'abord, nous proposons et démontrons une nouvelle conception de coupleurs contre-directionnels (contre-DC) dans laquelle un guide d'ondes SWG remplace l'un des guides d'ondes asymétriques des conceptions conventionnelles. Les dispositifs fabriqués sur la plate-forme SOI montrent une suppression supérieure à 35 dB du couplage codirectionnel indésirable et une plage spectrale supérieure à 120 nm sans interférence des réflexions intra-guides, grâce à l'important décalage de phase optique entre le guide d'onde segmenté SWG et son guide d'onde continu voisin. Nous étudions les effets de l'adaptation de la période du guide d'onde SWG, de la distance entre les deux guides et de la longueur de couplage sur les caractéristiques spectrales du dispositif, le changement de la distance entre 100 nm et 500 nm permettant des largeurs de bande de 18,2 nm. jusqu'à 0,9 nm. Ensuite, nous personnalisons les caractéristiques spectrales des contre-DC basées sur les SWG. En réduisant l'écart entre les guides d'ondes SWG et strip, nous démontrons un compromis entre la suppression des lobes latéraux et le taux d'extinction bande passante/arrêt afin d'améliorer les performances du dispositif en tant que multiplexeur optique à sauts optiques potentiels. Les conceptions avec différentes largeurs de bande passante de 12 nm, 9 nm et 6 nm montrent un rapport de suppression des lobes latéraux de 10 dB à 20 dB et un rapport d'extinction de 15 dB à 35 dB. Nous obtenons également un pic de transmission résonant dans la bande d'arrêt de la réponse spectrale du dispositif en introduisant un déphasage de π dans les réseaux du guide d'ondes SWG. Le pic de résonance a une largeur de bande de 1 nm et un taux d'extinction de 7 dB, l'utilisation du guide d'onde SWG dans la structure d'un tel coupleur permettant aux caractéristiques du pic de résonance d'être très sensibles au matériau de gaine applications.Enfin, dans la mesure où le multiplexage par répartition en longueur d'onde sur des liaisons optiques fournit une solution efficace au défi de la bande passante des communications hors puce et sur puce, nous présentons un multiplexeur optique goutte-à-goutte optique photonique silicium compact à quatre canaux, rendu possible par les contre-DC basées sur SWG. Les bandes passantes du dispositif montrent des pertes d'insertion sur la puce inférieures à 1,8 dB, avec une largeur de bande large de 3 dB, d'environ 6,7 nm, convenant au multiplexage par répartition en longueur d'onde grossière (CWDM) dans les applications d'interconnexion optique à courte portée. La transmission d'un flux de données de 10 Gbit/s à travers différents canaux du multiplexeur entraîne des pénalités de puissance négligeables, tandis que les pénalités de puissance induites par diaphonie sont inférieures à 2,8 dB

The efficacy of oral Lavandula angustifolia Mill. essential oil on menopausal symptoms, serum lipid profile, and cortisol concentration in postmenopausal women: A triple-blind, randomized, controlled trial

Objective: To determine the effect of oral Lavandula angustifolia Mill. essential oil (LEO) on menopausal symptoms, serum cortisol level, and lipid profile in postmenopausal women. Methods: This was a triple-blind parallel-armed randomized trial. Seventy-two postmenopausal women aged 50–65 years referring to healthcare centers in Tabriz, Iran with a score of 15–42 on the Green scale were included from May 10, 2022 to May 22, 2023. The participants were randomly assigned to two groups with a 1:1 ratio and using four and six blocks. One group received LEO soft gel 80 mg per day, and another group received a similar placebo for 60 days. A demographic questionnaire and a Greene menopause symptom scale were used for data collection. The lipid profile (total cholesterol, triglyceride, LDL, HDL) and the serum levels of cortisol were measured using biochemical methods. Chi-square, Fisher's exact tests, Independent samples t-test, Analysis of Covariance (ANCOVA), Repeated measure ANOVA, and Paired sample t-test were utilized for analyses. A p-value less than 0.05 was considered statistically significant. Results: The demographic and personal characteristics of the participants were similar. After two months of intervention, all symptoms in psychological, physical, vasomotor, anxiety, depression, and sexual dysfunction domains were significantly relieved (decreased) among both groups (p  0.05) in terms of studied serum markers. Conclusion: The oral LEO exhibited a significant enhancement in sexual dysfunction among postmenopausal women. Therefore, it can be used alongside other therapies to improve sexual dysfunction during menopause. LEO did not affect lipid profile and serum cortisol level in this study

The Effects of Lidocaine Reversible Inactivation of the Dorsal Raphe Nucleus on Passive Avoidance Learning in Rats

Introduction: The role of serotonergic fibers in avoidance learning is controversial. Involvement of the dorsal raphe nucleus (DRN), the main source of hippocampal projecting serotonergic fibers in acquisition, consolidation and retrieval of passive avoidance (PA) learning, was investigated by functional suppression of this area. Materials and Methods: DRN functional inactivation was done by lidocaine (0.5μl, 2%) injection into the DRN, 5 min before training (n=10); and 5 (n=9), 90 (n=10) and 360 min (n=9) after acquisition trial. In the last experiment, lidocaine was injected into the DRN 5 min before the retrieval test , which was 48 h after the training (n=10). Results: Our results showed that PA learning was not impaired by DRN inactivation 5 min before training nor 5 and 360 min after training. Lidocaine injected 90 min after the acquisition trial significantly reduced avoidance of the dark compartment (P<0.001). Intra-DRN injection of lidocaine before retrieval significantly increased PA retention (P<0.001). Therefore, it seems that DRN has opposite effects on consolidation and retrieval of passive avoidance learning, but it has no effect on PA acquisition. Discussion: It is suggested that functional ablation of DRN may disrupt integrity of subcortical circuits participating in PA consolidation, but DRN inactivation by increasing brain awareness may affect PA retrieval in rats