Electro-optically tunable optical delay on a lithium niobate photonic chip.

An approach for continuous tuning of on-chip optical delay with a microring resonator is proposed and demonstrated. By introducing an electro-optically tunable waveguide coupler, the bus waveguide to the resonance coupling can be effectively tuned from the under-coupling regime to the over-coupling regime. The optical delay is experimentally characterized by measuring the relative phase shift between lasers and shows a large dynamic range of delay from -600 to 600 ps and an efficient tuning of delay from -430 to -180 ps and from 40 to 240 ps by only a 5 V voltage.

Numerical analysis of on-chip acousto-optic modulators for visible wavelengths.

On-chip acousto-optic modulators that operate at an optical wavelength of 780 nm and a microwave frequency of 6.835 GHz are proposed. The modulators are based on a lithium-niobate-on-sapphire platform and efficiently excite surface acoustic waves and exhibit strong interactions with tightly confined optical modes in waveguides. In particular, a high-efficiency phase modulator and single-sideband mode converter are designed. We found that for both microwave and optical wavelengths below 1 µm, the interactions at the cross-sections of photonic waveguides are sensitive to the waveguide width and are significantly different from those in previous studies. Our designed devices have small footprints and high efficiencies, making them suitable for controlling rubidium atoms and realizing hybrid photonic-atomic chips. Furthermore, our devices have the potential to extend the acousto-optic modulators to other visible wavelengths for other atom transitions and for visible light applications, including imaging and sensing.

Synthetic five-wave mixing in an integrated microcavity for visible-telecom entanglement generation.

Nonlinear optics processes lie at the heart of photonics and quantum optics for their indispensable role in light sources and information processing. During the past decades, the three- and four-wave mixing (χ(2) and χ(3)) effects have been extensively studied, especially in the micro-/nano-structures by which the photon-photon interaction strength is greatly enhanced. So far, the high-order nonlinearity beyond the χ(3) has rarely been studied in dielectric materials due to their weak intrinsic nonlinear susceptibility, even in high-quality microcavities. Here, an effective five-wave mixing process (χ(4)) is synthesized by incorporating χ(2) and χ(3) processes in a single microcavity. The coherence of the synthetic χ(4) is verified by generating time-energy entangled visible-telecom photon pairs, which requires only one drive laser at the telecom waveband. The photon-pair generation rate from the synthetic process shows an estimated enhancement factor over 500 times upon intrinsic five-wave mixing. Our work demonstrates a universal approach of nonlinear synthesis via photonic structure engineering at the mesoscopic scale rather than material engineering, and thus opens a new avenue for realizing high-order optical nonlinearities and exploring functional photonic devices.

Efficient Frequency Conversion in a Degenerate χ

Microresonators on a photonic chip could enhance nonlinear optics effects and thus are promising for realizing scalable high-efficiency frequency conversion devices. However, fulfilling phase matching conditions among multiple wavelengths remains a significant challenge. Here, we present a feasible scheme for degenerate sum-frequency conversion that only requires the two-mode phase matching condition. When the drive and the signal are both near resonance to the same telecom mode, an on-chip photon-number conversion efficiency up to 42% is achieved, showing a broad tuning bandwidth over 250 GHz. Furthermore, cascaded Pockels and Kerr nonlinear optical effects are observed, enabling the parametric amplification of the optical signal to distinct wavelengths in a single device. The scheme demonstrated in this Letter provides an alternative approach to realizing high-efficiency frequency conversion and is promising for future studies on communications, atom clocks, sensing, and imaging.

All-optical thermal control for second-harmonic generation in an integrated microcavity.

Nonlinear optical effects in integrated microcavities have been studied extensively with the advantages of strong light-matter interaction, great scalability, and stability due to the small mode volume. However, the pump lasers stimulating nonlinear effects impose obstacles for practical applications, since the material absorption causes thermal resonance drift and instability. Here we experimentally demonstrate an all-optical control of the thermal behavior in optical microcavities for tunable doubly-resonant second-harmonic (SH) generation on an integrated photonic chip. Through an auxiliary control laser, the temperature of a selected microring can be efficiently changed, thus allowing precise frequency tuning of the doubly-resonant wavelength while eliminating the distortion of the lineshape induced by the thermo-optic effect. Although the phase-matching conditions will limit the tuning range of 55GHz, the technique is still potential to achieve a larger tuning range in combination with temperature regulation. Additionally, this approach has the advantage of quick reconfiguration, showing a fast modulation rate up to about 256 kHz. The theoretical model behind our experimental scheme is universal and applicable to other microcavity-enhanced nonlinear optical processes, and our work paves the way for controlling and utilizing the thermal effect in the applications of microcavities.

Environmental factors affecting self-management of chronic hepatitis B from the patients' perspective.

AIMS AND OBJECTIVES: To explore factors affecting self-management experiences of patients with chronic hepatitis B within their social and cultural environments. BACKGROUND: Many cases of hepatitis B are not detected until they are in end-stage liver disease. Despite an increasing trend of indicating a lack of health awareness as the reason, studies have rarely referred to the personal, social and cultural environmental constraints from patients' perspectives. DESIGN: A descriptive qualitative study. METHODS: Forty-seven adults diagnosed with chronic hepatitis B were interviewed in a private area of a hospital clinic in Taiwan in 2018. Four open-ended questions relating to care self-management included the following: disease detection; disease control; preventive care; and perceptions of screening and follow-ups. Data were examined using content analysis. This study also adhered to the consolidated COREQ guidelines. RESULTS: Five main themes emerged: personal experiences, awareness of occupational health, the availability of conventional treatment, cultural beliefs about health care and family roles. Findings of note were that some participants became aware that they had never known the difference between follow-up for hepatitis B and regular adult/labourer health checks due to a lack of information within their living environment. Many participants added alternative treatments to their self-management strategies and others frequently ignored follow-up appointments because of different cultural health beliefs. CONCLUSIONS: Patients' disease self-management perceptions are driven by dynamic influences suggesting that development of policies integrating personal, family, social and cultural environmental factors could enhance individual screening and subsequent health behaviours of patients with chronic hepatitis B. RELEVANCE TO PRACTICE: Adding person-centred case management of hepatitis B could enhance patients' adherence to follow-up. Attention should be given to increasing provider awareness of the influence of their own attitude and communication on patients' participation in self-management.

Comparison of cetuximab to bevacizumab as the first-line bio-chemotherapy for patients with metastatic colorectal cancer: superior progression-free survival is restricted to patients with measurable tumors and objective tumor response--a retrospective study.

PURPOSE: We aimed to compare the treatment efficacy of cetuximab versus bevacizumab in combination with either irinotecan-based or oxaliplatin-based regimens (targeted triplet) as the first-line treatment for patients with metastatic colorectal cancer. METHODS: Between April 2005 and March 2012, patients (n = 158) diagnosed with metastatic colorectal cancer after at least four courses of first-line bevacizumab-based (n = 95) or cetuximab-based triplet (n = 63) were retrospectively analyzed. The KRAS genotypes were sequenced for all patients. The Kaplan-Meier method was used for survival analysis, and Cox proportional hazards models were used for univariate and multivariate analyses. RESULTS: Cetuximab-based triplet was associated with a higher objective response rate (66.0 vs. 47.2 %, p = 0.037) and a higher conversion rate to resectability (39.7 vs. 20.0 %, p = 0.007) compared to bevacizumab-based triplet. Compared with bevacizumab-based triplet, cetuximab-based triplet significantly increased progression-free survival in patients with measurable metastatic colorectal cancer who achieved objective tumor response (responders) (median 13.1 vs. 10.5 months, p = 0.023), but no significant increase was observed for overall survival. After adjustment for group differences in baseline characteristics and combined chemotherapy agents, cetuximab-based triplet remained an independent determinant of progression-free survival in responders as compared with bevacizumab-based triplet. KRAS mutation was not a prognostic factor in patients with metastatic colorectal cancer. CONCLUSIONS: As compared with bevacizumab-based triplet, cetuximab-based triplet as the first-line treatment of metastatic colorectal cancer was associated with better progression-free survival in patients with measurable tumors who achieved objective tumor response to bio-chemotherapy.

Both gefitinib and erlotinib induced drug-related interstitial lung disease in a patient with pulmonary adenocarcinoma.

Treatment for non-small-cell lung cancer with gefitinib and erlotinib is efficacious. However, while many studies have reported on gefitinib-related interstitial lung disease (ILD), less published data are available regarding erlotinib-induced ILD. Here, we report a case of pulmonary adenocarcinoma who developed ILD due to gefitinib initially and erlotinib thereafter. The two episodes of ILD were treated successfully with the discontinuation of the tyrosine kinase inhibitors and high-dose intravenous corticosteroids.