Low-loss multimode interference couplers for terahertz waves

The terahertz (THz) frequency region of the electromagnetic spectrum is located between the traditional microwave spectrum and the optical frequencies, and offers a significant scientific and technological potential in many fields, such as in sensing, in imaging and in spectroscopy. Waveguiding in this intermediate spectral region is a major challenge. Amongst the various THz waveguides suggested, metal-clad plasmonic waveguides and specifically hollow core structures, coated with insulating material are the most promising low-loss waveguides used in both active and passive devices. Optical power splitters are important components in the design of optoelectronic systems and optical communication networks such as Mach-Zehnder Interferometric switches, polarization splitter and polarization scramblers. Several designs for the implementation of the 3dB power splitters have been proposed in the past, such as the directional coupler-based approach, the Y-junction-based devices and the MMI-based approach. In the present paper a novel MMI-based 3dB THz wave splitter is implemented using Gold/polystyrene (PS) coated hollow glass rectangular waveguides. The H-field FEM based full-vector formulation is used here to calculate the complex propagation characteristics of the waveguide structure and the finite element beam propagation method (FE-BPM) and finite difference time domain (FDTD) approach to demonstrate the performance of the proposed 3dB splitter

Demonstration of Polarization-Independent Surface Plasmon Resonance Polymer Waveguide for Refractive Index Sensing

The effect of the variation of the refractive index in a gold-coated ormocomp waveguide for sensing application is studied in this paper. The ormocomp waveguide is fabricated by using the nanoimprint method. A waveguide with width and height both equal to 10 μm is coated with 100 nm thick gold using the sputtering technique in order to introduce surface plasmon resonance at the vertical sides and also at the top of the structure. Here, polarization-independent waveguide is achieved by supporting both the plasmonic TE and TM modes and the light confinement in these modes are studied. Supermodes forming from coupling between the fundamental dielectric mode and the plasmonic supermode at the resonance peak are also investigated. This paper presents the numerical simulated results and also their experimental validations. For this structure, there are two dielectric-plasmon supermodes with two resonance peaks separated by 50 nm. A red shift is observed when the refractive index of the cladding material increases. The cladding material includes water (n = 1.333) and iso-propanol solutions with refractive indices of 1.344, 1.351, and 1.365. The gold-coated ormocomp waveguide has sensitivity of about 544.55 nm/RIU with a resolution of 5.3 × 10⁻³ RIU

Low-loss multimode interference couplers for terahertz waves

The terahertz (THz) frequency region of the electromagnetic spectrum is located between the traditional microwave spectrum and the optical frequencies, and offers a significant scientific and technological potential in many fields, such as in sensing, in imaging and in spectroscopy. Waveguiding in this intermediate spectral region is a major challenge. Amongst the various THz waveguides suggested, metal-clad plasmonic waveguides and specifically hollow core structures, coated with insulating material are the most promising low-loss waveguides used in both active and passive devices. Optical power splitters are important components in the design of optoelectronic systems and optical communication networks such as Mach-Zehnder Interferometric switches, polarization splitter and polarization scramblers. Several designs for the implementation of the 3dB power splitters have been proposed in the past, such as the directional coupler-based approach, the Y-junction-based devices and the MMI-based approach. In the present paper a novel MMI-based 3dB THz wave splitter is implemented using Gold/polystyrene (PS) coated hollow glass rectangular waveguides. The H-field FEM based full-vector formulation is used here to calculate the complex propagation characteristics of the waveguide structure and the finite element beam propagation method (FE-BPM) and finite difference time domain (FDTD) approach to demonstrate the performance of the proposed 3dB splitter

Realization of a polymer nanowire optical transducer by using the nanoimprint technique

An optical transducer using an integrated optics polymer nanowire is proposed. The nanoimprint technique is used to fabricate an OrmoComp nanowire with 1.0 μm width and 0.5 μm height, but the resulting sidewalls are not perfectly vertical. Maximum sensitivity is achieved by enhancing the evanescent field in the cladding region. The possible mode fields and power confinement of the nanowire are studied with respect to their structural dimensions, the operating wavelength, and the cladding material by using th

Characterization of polymer nanowires fabricated using the nanoimprint method

In this paper, an ormocomp polymer nanowire with possible use in integrated-optics sensing applications is presented. We discuss the structure design, the fabrication process and present results of the simulation and characterization of the optical field profile. Since the nanowires are designed and intended to be used as integrated optics devices, they are attached to tapered and feed waveguides at their ends. The fabrication process in this work is based mainly on the nanoimprint technique. The method assumes a silicon nanowire as an original pattern, and polydimethylsiloxane (PDMS) as thesoft mold. The PDMS mold is directly imprinted on the ormocomp layer and then cured by UV light to form the polymer based nanowire. The ormocomp nanowires are fabricated to have various dimensions of width and length at a fixed 500nm thickness. The length of the nanowires is varied from 250 μm to 2 mm, whereas the width of the structures is varied between 500nm and 1μm. The possible optical mode field profile that occurs in the proposed polymer nanowire design is studied using the H-field finite element method (FEM). In the characterization part, the optical field profile and the intensity at the device output are the main focus of this paper. The various lengths of the nanowires show different characteristics in term of output intensity. An image processing is used to process the image to obtain the intensity of the output signal. A comparison of the optical field and output intensity for each polymer nanowire is also discussed

Reliability of fibre Bragg gratings in polymer optical fibre

In this paper we report on investigations of some of the factors that have a bearing on the reliability and repeatability of polymer fibre Bragg gratings. The main issues discussed are the fibre preform composition, the fibre drawing conditions and the thermal history of the fibre grating

Electrically tunable Bragg gratings in single mode polymer optical fiber

We present what is to our knowledge the first demonstration of a tunable fiber Bragg grating device in polymer optical fiber that utilizes a thin-film resistive heater deposited on the surface of the fiber. The polymer fiber was coated via photochemical deposition of a Pd/Cu metallic layer with a procedure induced by vacuum-ultraviolet radiation at room temperature. The resulting device, when wavelength tuned via joule heating, underwent a wavelength shift of 2 nm for a moderate input power of 160 mW, a wavelength to input power coefficient of-13.4 pm/mW, and a time constant of 1.7 s-1

The Relationship Between Availability and Changes to Perceived Workplace Support and Their Impact on the Mental Health, Well-being and Burn-Out of Healthcare Professionals (HCP): Insight and Mitigating Strategies From the CoPE-HCP Cohort Study

AIMS: To examine the relationship between self-reported level of workplace support (WS) and various mental health outcomes in HCPs and non-HCPs at different time-points during the COVID-19 pandemic, and to examine whether improved WS is associated with improved mental health outcomes over time. Lastly, to identify what support healthcare professionals (HCPs) perceive to be most helpful. METHODS: Cohort survey study at baseline (July-September 2020) and follow-up (approximately four months later). Setting HCPs working in primary or secondary care, from UK and other countries, and non-HCP controls from primarily London-based universities. Participants 1574 HCPs and 147 non-HCPs (academic and research staff at London-based universities). The inclusion criteria for the study were: 1) aged 18 or older, 2) electronic consent given, and 3) identified as HCP or non-healthcare academic staff or self-declared non-HCPs. Main outcome measures Presence of generalized anxiety disorder (assessed using the GAD-7), clinical insomnia (ISI), major depressive disorder (PHQ-9), well-being (SWEMWBS), and burnout (emotional exhaustion and depersonalization; EEDP2Q). Qualitative data exploring what support HCPs perceive as most useful was gathered using free-text inputs. RESULTS: At baseline and follow-up, consistently, compared to those who felt unsupported, those who felt supported had significantly reduced risk (odds) of generalized anxiety disorder (baseline: 59% [95% CI of OR, 0.29 to 0.57], follow-up: 41% [0.38 to 0.92]), clinical insomnia (51% [0.34 to 0.69], 66% [0.20 to 0.55]), major depressive disorder (58% [0.31 to 0.58], 54% [0.31 to 0.74]), emotional exhaustion (65% [0.26 to 0.46], 61% [0.27 to 0.56]) and depersonalization (58% [0.28 to 0.61], 68% [0.21 to 0.50]). At follow-up, self-reported improved WS (vs. baseline) was associated with significantly improved GAD-7 (adjusted difference. −1.73 [-2.54 to −0.91]), ISI (-0.96 [-1.88 to −0.04]), PHQ−9 (-1.32 [-2.16 to −0.49]), SWEMWBS (0.97 [0.37 to 1.57]) and EEDP2Q (burnout) (-1.30 [-1.82 to −0.79]) scores, independent of baseline level of support. Five themes were identified constituting WS: ‘managerial support’ was the largest sub-theme. CONCLUSION: A consistent association was observed between level of WS and the mental health of HCPs and non-HCPs. Improved WS was associated with improved mental health scores over a four-month period during the pandemic

Assessing crossnational invariance of the three-component model of organizational commitment:A cross-country study of university faculty

Purpose The purpose of this paper is to examine affective commitment, normative commitment, and continuance commitment in a cross-national context to identify if the effect of country-specific cultural orientation on organizational commitment of faculty in higher education functions invariably in different countries. Design/methodology/approach The work expands on Meyer and Allen’s (1991) three-component model of organizational commitment. It includes relevant literature review on ten countries and the results of a survey of university faculty members, assessing their institutions’ human resources practices and their effect on organizational commitment. Basic descriptive statistics were performed on nominal and interval data, means, medians, and standard deviations were computed, and tests of mean equivalence, including ANOVA tests, were performed. In certain instances, Pearson and Spearman correlations were computed to ascertain correlation, and χ2 tests for randomized response were used, while Cronbach’s α test helped to establish survey instrument validity. Findings Though certain differences may exist between different countries and cultures with respect to the three-component model of organizational commitment, there is strong evidence of the existence of invariance and, thus, generalizability of the model across cultures. Research limitations/implications Cultural studies have focused on differences in organizational commitment at national levels. Further attempts to identify the universality of factors leading to organizational commitment should account for culture in the study of employee-related globalization issues in higher education institutes. Knowledge of cultural impact is also useful from a managerial perspective, and for the design of relevant strategies. Practical implications National context plays a major role in shaping the nature of educational institutions. This study brings out the need for a deeper understanding of invariance in organizational commitment (inter-alia, through the three-component model). Originality/value This study contributes to a better understanding of the relationship between organizational commitment and its various antecedents, including human resources management practices, for faculty in higher education institutes