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Silicon photonics has been studied in various areas by providing small-footprint, high-performance, and mass-producible optoelectronic components integrated on a chip. For the photonic packaging, ultraviolet (UV) curing techniques have been widely utilized. Meanwhile, silica cladding absorption to UV light could alter its refractive index (RI), affecting the optical testing of silicon devices during or after the device packaging. Therefore, it is significant to characterize the dynamics of RI changes induced by UV-light irradiation. However, the in-situ characterization of such devices is seldom explored. Here, we studied the influence of UV-light irradiation on silicon photonic devices by probing resonant wavelength shifts of a racetrack microring resonator. Specifically, we studied the temporary variation of the resonant wavelength and its recovery time under different UV-light exposure durations. Experimental results show that with a UV energy of 21 J/cm2, the resonator had a maximum resonant wavelength shift of 0.31 nm, corresponding to an effective RI change of 0.0009 and recovering time of 95 minutes. Based on the experimental results, we compressively analyzed and compared RI changes induced by plasmon dispersion effect, thermal optical effect and photon-induced silica densification effect. Our study is expected to provide useful guidelines for in-situ silicon photonic testing and packaging.

On-chip optical gas sensors, which use resonant shifts of cavities to detect molecular concentrations, have the advantages of high sensitivity, real-time detection, and compact footprint. However, such sensors are usually limited by a serious cross-sensitivity issue induced by environmental temperature variations. To overcome this limitation, we study a dual-mode graphene-on-microring resonator to accurately measure gas concentrations without suffering from temperature variations. To be specific, the influences of gas-induced graphene’s optical conductivity changes and environmental temperature variations on effective refractive indices of TE0 and TE1 modes in the resonator can be decoupled based on the modal linear independent responses. With this method, we designed a nitrogen dioxide sensor with a sensitivity of 0.02 nm/ppm and a limit of detection of 0.5 ppm. Our study paves the way for developing on-chip optical gas sensors with excellent sensitivity and temperature stability.

The on-chip mode-division multiplexing (MDM) is an attractive technique to achieve high-capacity optical transmissions by using a single-wavelength carrier. In traditional schemes, multiple channels with a fundamental mode are modulated by parallel arranged electro-optic modulators and then converted to high-order modes. However, the method is usually limited by large device footprints and high energy consumption. In this work, we study a graphene-based waveguide-integrated multimode phase modulator to individually modulate TE0 and TE1 modes in a multimode waveguide device. To be specific, we designed a single layer of graphene narrow strips (GNSs) integrated on the surface of the multimode waveguide device to selectively introduce contrasting phase shifts to different modes. Based on the optimized waveguide structures, a Mach-Zehnder interferometer modulator with different GNS patterns on each arm is designed. Our study is promising to be used in the future high-density on-chip MDM systems for optical interconnects and optical networks.

BackgroundThis study aimed to assess the clinical utility of the advanced lung cancer inflammation index (ALI) as a prognostic indicator for patients with cholangiocarcinoma (CCA) and construct a prognostic nomogram based on ALI.MethodsA total of 97 CCA patients who received radical resection were included. The optimal cut-off point for ALI was identified by X-tile analysis. COX regression analysis were used to identify risk factors of overall survival (OS) and disease-free survival (DFS). A predictive nomogram for DFS was constructed.ResultsThe optimal cut-off value for preoperative ALI was 31.8. 35 (36.1%) patients were categorized into the low-ALI group and 62 (63.9%) patients into the high-ALI group. Low ALI was independently associated with hypoproteinemia and lower body mass index (BMI) (all P < 0.05). COX regression analysis revealed that preoperative ALI level (HR = 0.974, P = 0.037) and pathological TNM stage (HR = 7.331, P < 0.001) were independently correlated with OS for patients with CCA, and preoperative ALI level (HR = 0.978, P = 0.042) and pathological T stage (HR = 1.473, P = 0.035) remained to be independent prognostic factors for DFS in CCA patients. Using time-dependent ROC analysis, we found that ALI was better at predicting prognosis than other parameters, such as neutrophil-to-lymphocyte ratio (NLR), monocyte-to-lymphocyte ratio (MLR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and prognostic nutritional index (PNI) in terms of OS and DFS. A nomogram predicting DFS was built (C-index: 0.73 95%CI: 0.67–0.79).ConclusionsALI may be useful for prognosis assessment for patients with CCA.