1,721,033 research outputs found
Apodized focusing subwavelength grating couplers for suspended membrane waveguides
No full textWe demonstrate an apodized focusing subwavelength grating (SWG) for suspended membrane waveguides on silicon-on-insulator. Finite-difference time-domain simulation predicts -1.7 dB coupling efficiency and a 3 dB bandwidth of similar to 50 nm for the transverse-magnetic mode apodized SWG, which has 98% field overlap with propagation mode in the single mode fiber. A modified phase matching formula is proposed to design the focusing apodized SWG. Better than -3.0 dB coupling efficiency and a 3 dB optical bandwidth of similar to 50 nm is demonstrated experimentally
Integrated optical spectrometers on silicon photonics platforms
No full textSpectroscopy plays a pivotal role in discerning the chemical and biochemical compositions of analytes, significantly impacting chemical and material analysis, disease diagnosis, environmental monitoring, and space exploration. Despite the widespread demand for optical spectrometers in both industry and academia, their deployment in many practical applications is hindered by the high costs, large footprints, and mechanical vibration sensitivity of conventional spectrometers. These problems are addressed by integrated optical spectrometers. Silicon photonics offers a potentially low-cost platform for ultracompact integrated optical spectrometers, leveraging the complementary metal-oxide-semiconductor (CMOS) compatible fabrication technology and high flexibility in on-chip light manipulation of high-index waveguides. The integrated optical spectrometers on silicon photonics platforms provide promising solutions for developing ultra-compact and cost-effective spectral analyzers in various applications. This review paper overviews recent advancements in integrated optical spectrometers on silicon photonics platforms over the past decades, focusing on their fundamental principles, design methodologies, spectral performances, and potential applications. By blending foundational knowledge with cutting-edge research, this review aims to involve researchers from different fields, including spectroscopy, materials science, astronomy, environmental engineering, and beyond.</p
Machine learning adaptive receiver for PAM-4 modulated optical interconnection based on silicon microring modulator
No full textModulation nonlinearity can severely distort multi-level modulation, and signal processing to mitigate the distortion is highly desirable. In this work, we demonstrated a machine learning method for adaptive detection of 4-level pulse amplitude modulation (PAM-4) signals modulated by silicon micro-ring modulator (Si-MRM). The very limited linear modulation range of Si-MRM leads to serious modulation nonlinearity distortion for high-level modulations like PAM-4 with the consideration of wavelength drift. Our approach is based on the support vector machine (SVM) method which can learn the nonlinear distortion of Si-MRM during PAM-4 modulation. Thus, the detection can be made adaptive for PAM-4 signals with nonlinear levels and level dependent noise. The modulation nonlinearity distortion of PAM-4 has been characterized in terms of level deviation (LD) with respect to wavelength drift. Up to 2.7-dB receiver sensitivity gain is obtained at about 26% LD by using the proposed SVM machine learning method. The receiver sensitivity-float range can be squeezed to be within 0.3 dB even with up to 30% LD which indicates a stable detection of PAM-4 signals along with wavelength drift. Up to 3.63-dB receiver sensitivity improvement has been experimentally achieved at 50 Gbps for PAM-4 signals modulated by a Si-MRM and after 2-km standard single mode fiber (SSMF) transmission. The stable operation of Si-MRM is very difficult and very important. The proof-of-concept results indicate the very promising capability of machine learning method for stable detection of PAM-4 signals modulated by Si-MRM, which is of great significance for practical application of Si-MRM in optical interconnection.</p
Subwavelength Silicon Photonics
No full textSubwavelength gratings refer to periodic structures that have a period less than half the wavelength of light in the material so that no Bragg diffraction mode is supported. Instead, the light will propagate as if it was in a homogeneous material with anisotropic refractive indices. Subwavelength gratings have attracted great interest recently, as they provide a useful degree of freedom for the crafting of the effective refractive index of the material in photonic devices. In this chapter, we will introduce some of the applications of subwavelength structures for silicon photonics devices. We start by introducing the background theory of subwavelength gratings and then discuss their applications for the engineering of waveguide grating couplers, suspended membrane devices for mid-infrared (mid-IR) wavelengths, and their use with numerical optimization techniques for optimizing photonic devices. We shall discuss the classic effective medium theory (EMT) for subwavelength gratings and show how EMT can reduce time-consuming three-dimensional (3D) numerical optimizations to an effective two-dimensional (2D) optimization problem
Polarization dependent loss of graphene-on-silicon waveguides
No full textWe represent the polarization dependent loss of graphene placed directly onto silicon waveguides. Graphene introduces 7.7 dB higher losses for TM mode in a 150 µm long waveguide, which is sufficient for an integrated polarizer
Integrated Plasmonic Infrared Photodetector Based on Colloidal HgTe Quantum Dots
No full textThis paper presents a 2300 nm wavelength photodetector which comprises a spin-deposited colloidal HgTe quantum dot (QD) film on a metal-insulator-metal (MIM) plasmonic waveguide. This photodetector is an integrated device based on the complementary metal-oxide-semiconductor compatible silicon-on-insulator platform. The device employs input and output silicon waveguide grating couplers, and HgTe QDs are used as the infrared photosensing material. Infrared light is coupled to the strongly confined MIM waveguide mode, which shrinks the device footprint and improves the light detection efficiency simultaneously. A room temperature responsivity of 23 mA W−1 and a noise-equivalent power of 8.7 × 10−11 W Hz−1/2 at 2300 nm wavelength are achieved by the photodetector at 2.14 W mm−2 (measured at the input to the plasmonic waveguide) with a device footprint of 15 µm × 0.35 µm. The light intensity–dependent photocurrent, the current noise spectral density, and the 3 dB operation bandwidth are all characterized. The charge transfer properties of the organic HgTe QD films are further analyzed based on field effect transistor measurements
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Guest Editorial Introduction to the JSTQE Issue on Advanced Photonic Modulation : Devices, Systems & Techniques
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