Partial coherence enhances parallelized photonic computing.

Advancements in optical coherence control1-5 have unlocked many cutting-edge applications, including long-haul communication, light detection and ranging (LiDAR) and optical coherence tomography6-8. Prevailing wisdom suggests that using more coherent light sources leads to enhanced system performance and device functionalities9-11. Our study introduces a photonic convolutional processing system that takes advantage of partially coherent light to boost computing parallelism without substantially sacrificing accuracy, potentially enabling larger-size photonic tensor cores. The reduction of the degree of coherence optimizes bandwidth use in the photonic convolutional processing system. This breakthrough challenges the traditional belief that coherence is essential or even advantageous in integrated photonic accelerators, thereby enabling the use of light sources with less rigorous feedback control and thermal-management requirements for high-throughput photonic computing. Here we demonstrate such a system in two photonic platforms for computing applications: a photonic tensor core using phase-change-material photonic memories that delivers parallel convolution operations to classify the gaits of ten patients with Parkinson's disease with 92.2% accuracy (92.7% theoretically) and a silicon photonic tensor core with embedded electro-absorption modulators (EAMs) to facilitate 0.108 tera operations per second (TOPS) convolutional processing for classifying the Modified National Institute of Standards and Technology (MNIST) handwritten digits dataset with 92.4% accuracy (95.0% theoretically).

Scalable High-Precision Trimming of Photonic Resonances by Polymer Exposure to Energetic Beams.

Integrated photonic circuits (PICs) have seen an explosion in interest, through to commercialization in the past decade. Most PICs rely on sharp resonances to modulate, steer, and multiplex signals. However, the spectral characteristics of high-quality resonances are highly sensitive to small variations in fabrication and material constants, which limits their applicability. Active tuning mechanisms are commonly employed to account for such deviations, consuming energy and occupying valuable chip real estate. Readily employable, accurate, and highly scalable mechanisms to tailor the modal properties of photonic integrated circuits are urgently required. Here, we present an elegant and powerful solution to achieve this in a scalable manner during the semiconductor fabrication process using existing lithography tools: by exploiting the volume shrinkage exhibited by certain polymers to permanently modulate the waveguide's effective index. This technique enables broadband and lossless tuning with immediate applicability in wide-ranging applications in optical computing, telecommunications, and free-space optics.

Varifocal Metalens Using Tunable and Ultralow-loss Dielectrics.

The field of flat optics that uses nanostructured, so-called metasurfaces, has seen remarkable progress over the last decade. Chalcogenide phase-change materials (PCMs) offer a promising platform for realizing reconfigurable metasurfaces, as their optical properties can be reversibly tuned. Yet, demonstrations of phase-change metalenses to date have employed material compositions such as Ge2 Sb2 Te5 , which show high absorption in the visible to near-IR wavelengths particularly in their crystalline state, limiting the applicability. Here, by using a low-loss PCM Sb2 Se3 , for the first time, active polarization-insensitive phase-change metalenses at near-IR wavelengths with comparable efficiencies in both material states are shown. An active metalens with a tunable focusing intensity of 95% and a focusing efficiency of 23% is demonstrated. A varifocal metalens is then demonstrated with a tunable focal length from 41 to 123 µm with comparable focusing efficiency (5.7% and 3%). The ultralow-loss nature of the material introduces exciting new possibilities for optical communications, multi-depth imaging, beam steering, optical routing, and holography.

Polarization-selective reconfigurability in hybridized-active-dielectric nanowires.

Wavelength and polarization are two fundamental properties of light within which information can be encoded and (de)multiplexed. While wavelength-selective systems have widely proliferated, polarization-addressable active photonics has not seen notable progress, primarily because tunable and polarization-selective nanostructures have been elusive. Here, we introduce hybridized-active-dielectric (HAD) nanowires to achieve polarization-selective tunability. We then demonstrate the ability to use polarization as a parameter to selectively modulate the conductance of individual nanowires within a multi-nanowire system. By using polarization as the tunable vector, we show matrix-vector multiplication in a nanowire device configuration. While our HAD nanowires use phase-change materials as the active material, this concept is readily generalized to other active materials hybridized with dielectrics and thus has the potential in a broad range of applications from photonic memories and routing to polarization-multiplexed computing.

Electronically Reconfigurable Photonic Switches Incorporating Plasmonic Structures and Phase Change Materials.

The ever-increasing demands for data processing and storage will require seamless monolithic co-integration of electronics and photonics. Phase-change materials are uniquely suited to fulfill this function due to their dual electro-optical sensitivity, nonvolatile retention properties, and fast switching dynamics. The extreme size disparity however between CMOS electronics and dielectric photonics inhibits the realization of efficient and compact electrically driven photonic switches, logic and routing elements. Here, the authors achieve an important milestone in harmonizing the two domains by demonstrating an electrically reconfigurable, ultra-compact and nonvolatile memory that is optically accessible. The platform relies on localized heat, generated within a plasmonic structure; this uniquely allows for both optical and electrical readout signals to be interlocked with the material state of the PCM while still ensuring that the writing operation is electrically decoupled. Importantly, by miniaturization and effective thermal engineering, the authors achieve unprecedented energy efficiency, opening up a path towards low-energy optoelectronic hardware for neuromorphic and in-memory computing.

Ultrahigh resolution and color gamut with scattering-reducing transmissive pixels.

While plasmonic designs have dominated recent trends in structural color, schemes using localized surface plasmon resonances and surface plasmon polaritons that simultaneously achieve high color vibrancy at ultrahigh resolution have been elusive because of tradeoffs between size and performance. Herein we demonstrate vibrant and size-invariant transmissive type multicolor pixels composed of hybrid TiOx-Ag core-shell nanowires based on reduced scattering at their electric dipolar Mie resonances. This principle permits the hybrid nanoresonator to achieve the widest color gamut (~74% sRGB area coverage), linear color mixing, and the highest reported single color dots-per-inch (58,000~141,000) in transmission mode. Exploiting such features, we further show that an assembly of distinct nanoresonators can constitute a multicolor pixel for use in multispectral imaging, with a size that is ~10-folds below the Nyquist limit using a typical high NA objective lens.

Electrocatalytic glycerol oxidation enabled by surface plasmon polariton-induced hot carriers in Kretschmann configuration.

Plasmonic hot carrier generation has attracted increasing attention due to its ability to convert light to electrical energy. The generation of plasmon-induced hot carriers can be achieved via Landau damping in the non-radiative decay process of the plasmonic excitation energy. Localized surface plasmons (LSPs) undergo both radiative and non-radiative decays, while surface plasmon polaritons (SPPs) dissipate only via the non-radiative decay. Thus, it is a challenging task to exploit the surface plasmon polaritons for the efficient generation of hot carriers and their applications. In this study, a model hot-carrier-mediated electrocatalytic conversion system was demonstrated using an Au thin film in Kretschmann configuration, which is the representative platform to excite SPPs. AgPt-decorated Au nanobipyramids (AuNBPs) were designed and introduced onto the Au film, creating hot-spots to revolutionize the thin film-based photon-to-carrier conversion efficiency. The glycerol electro-oxidation reaction enabled by such SPP-induced hot carriers was evaluated and exhibited a photon-to-hot carrier conversion efficiency of 2.4 × 10-3%, which is ∼2.5 times enhanced as compared to the efficiency based on the neat Au film.

Diagnosis and treatment of metachronous gastric cancers after surgical treatment for esophageal squamous cell carcinoma.

BACKGROUND/AIMS: With the improvement of the outcome after esophagectomy for esophageal cancer, patients with metachronous gastric cancer (MGC) in the reconstructed thoracic stomach have been observed in clinical practice. This study is a report of experiences with MGC with an emphasis on clinical pictures and treatment results. METHODOLOGY: Medical records were reviewed of 728 patients who underwent surgery for esophageal cancer at Samsung Medical Center between 1994 and 2004. MGC was defined as follows; (1) diagnosed more than 6 months after esophagectomy, (2) squamous cell carcinoma in histology of the surgically resected esophagus, (3) adenocarcinoma in histology of the stomach biopsy or surgical specimen. The clinicopathologic characteristics of MGC were evaluated. RESULTS: Eight patients (1.1%) of 728 patients were diagnosed with MGC. All patients were male and had a history of active smoking and drinking. The median age at the time of diagnosis of MGC was 67.8 years old (range: 62-76). Three patients (37.5%) were asymptomatic. Two patients (25%) complained of epigastric pain and 3 patients (37.5%) complained of obstructive symptoms including regurgitation, aspiration, dysphagia, and vomiting. The median interval between diagnosis of MGC and esophagectomy was 37 months (range: 8-85). Three MGCs (37.5%) were detected by endoscopic examination but not by computed tomography (CT). Three patients (37.5%) received surgery and were alive without recurrence for 12, 18 and 63 months respectively. One patient (12.5%) received radiation therapy and was alive for 69 months. Four patients (50%) received no treatment because of follow-up loss in 2 patients (25%) and death within days of MGC diagnosis in 2 patients (25%). CONCLUSIONS: Favorable outcomes can be obtained by active treatment in patients with MGC after esophagectomy. Regular endoscopic follow-up is important for early detection and more effective treatment of MGC, especially in areas where the incidence of gastric cancer is high.

[An evaluation of web-based informations about gastroesophageal reflux diseases in Korea].

BACKGROUND/AIMS: Internet has become an important source of medical information not only for medical personnels but also for patients. The aim of this study was to evaluate the quality of internet based medical information about 'gastroesophageal reflux' or 'reflux esophagitis' in Korea. METHODS: The first 15 internet sites using the key words 'gastroesophageal reflux' or 'reflux esophagitis' were retrieved from the 7 most frequently used internet search engines. The quality of information from a total of 108 websites was evaluated using a checklist. RESULTS: Among total 108 sites related to 'gastroesophageal reflux' or 'reflux esophagitis', fifty-six sites (51.8%) were made by hospitals or clinics and 94 sites (87.0%) were made for patients. Of the 108 sites, eleven web sites (10.1%) had more than three JAMA benchmarks (authorship, references, currency, and disclosure). Higher quality sites (at least three JAMA benchmarks) were less likely to contain inaccurate information than lower quality sites (fewer than three JAMA benchmarks)-3/11 (27.2%) vs. 60/97 (61.9%) (p<0.01). Despite the fact that articles in the literature emphasized an insufficient evidence to support an association between the lifestyle, dietary behaviors, and GERD, such guidelines continue to be recommended as first-line therapy in most websites. CONCLUSIONS: Informations about gastroesophageal reflux disease were incomplete in the majority of medical web sites. These would bring about confusion to patients seeking for an information about GERD through the internet. There is a need for better sources in evidence based informations about gastroesophageal reflux diseases on the web.

Functional conductive nanomaterials via polymerisation in nano-channels: PEDOT in a MOF.

Reactions inside the pores of metal-organic frameworks (MOFs) offer potential for controlling polymer structures with regularity to sub-nanometre scales. We report a wet-chemistry route to poly-3,4-ethylenedioxythiophene (PEDOT)-MOF composites. After a two-step removal of the MOF template we obtain unique and stable macroscale structures of this conductive polymer with some nanoscale regularity.

[Comparative usefulness of erythrocyte sedimentation rate and C-reactive protein in assessing the severity of ulcerative colitis].

BACKGROUND/AIMS: Although erythrocyte sedimentation rate (ESR) is included as a laboratory parameter in Truelove and Witts' classification, C-reactive protein (CRP) is also used for severity assessment in ulcerative colitis (UC). Frequently, the discordance between ESR and CRP is observed in clinical practice. The aim of this study was to determine which parameter is more related with clinical activity in UC patients. METHODS: A total of 155 patients with UC were identified from January 2004 to March 2005. Their medical records were reviewed within these patients, a total of 541 assessments of disease activity were made. Correlation of clinical activity and laboratory tests were evaluated by Pearson's correlation coefficient. RESULTS: Pearson's correlation coefficients of ESR and CRP with clinical symptoms were 0.376 and 0.258, respectively. The correlation coefficient between ESR and CRP was 0.403 (p=0.000). A total of 131 (24.2%) assessments revealed discordance between ESR and CRP. When discordance occurred, the correlation coefficients with clinical symptoms were 0.338 for ESR (p=0.000) and 0.034 for CRP (p>0.01). Dividing discordant patients into high ESR/low CRP group and low ESR/high CRP group, the coefficients were 0.420 for ESR and 0.226 for CRP in high ESR/low CRP group, and 0.333 for ESR and 0.068 for CRP in low ESR/high CRP group. CONCLUSIONS: The correlation analysis indicates that ESR appears to be a more reliable laboratory parameter of disease activity than CRP in assessing the severity of UC. In particular, when the level of ESR and CRP is discordant, ESR is more useful in assessing the disease activity in UC patients.