Dual-comb mode-locked Yb:CALGO laser based on cavity-shared configuration with separated end mirrors

Dual-comb spectroscopy typically requires the utilization of two independent and phase-locked femtosecond lasers, resulting in a complex and expensive system that hinders its industrial applications. Single-cavity dual-comb lasers are considered as one of the primary solution to simplify the system. However, controlling the crucial parameter of difference in repetition rates remains challenging. In this study, we present a dual-comb mode-locked Yb:CALGO laser based on a cavity-shared configuration with separated end mirrors. We employ two pairs of end mirrors and two thin-film polarizers angled at 45 degrees to the cavity axis, leading to separating the cross-polarized laser modes. We achieve simultaneous operation of two combs at approximately 1040 nm with pulse durations of around 400 fs and an average power exceeding 1 W. The repetition rates are approximately 59 MHz and their difference can be easily tuned from zero up to the MHz range. By effectively canceling out common mode noises, we observe minimal fluctuation in the repetition rate difference with a standard deviation of about 1.9 Hz over ten minutes, while experiencing fluctuations in repetition rates as large as 90 Hz. We demonstrate the capabilities of this system by utilizing the free-running dual-comb setup for asynchronous optical sampling on a saturable absorber and measuring etalon transmission spectrum. This system allows for simple and independent control of the repetition rates and their difference during operation, facilitating the selection of optimal repetition rate difference and implementation of phase-locking loops. This advancement paves the way for the development of simple yet high-performance dual-comb laser sources

Calibration plot relative F/F₀ of the PG/aptamer duplex mixture against different concentrations of OTA in 1% beer.

<p>F₀ and F stand for the fluorescent intensity in the absence and presence of OTA.</p

Label-free aptasensor using PG for detection of OTA.

<p>(A) Fluorescence spectra of the PG/aptamer duplex mixture in the presence of various concentrations of OTA. (B) Calibration plot relative F/F₀ of the PG/aptamer duplex mixture against different concentrations of OTA. F₀ and F stand for the fluorescent intensity in the absence and presence of OTA.</p

Schematic illustration of fluorescent detection of OTA by a label-free aptasensor.

<p>Schematic illustration of fluorescent detection of OTA by a label-free aptasensor.</p

Aptamer and complementary sequences used in this study.

<p>Aptamer and complementary sequences used in this study.</p

Selectivity evaluation the aptasensor for OTA.

<p>(A) Against NAP and ZEN in same series concentrations. (B) Using a chloramphenicol aptamer and its complementary strand.</p

Designing Reactive Bridging O^2– at the Atomic Cu–O–Fe Site for Selective NH₃ Oxidation

Surface oxidation chemistry involves the formation and breaking of metal–oxygen (M–O) bonds. Ideally, the M–O bonding strength determines the rate of oxygen absorption and dissociation. Here, we design reactive bridging O2– species within the atomic Cu–O–Fe site to accelerate such oxidation chemistry. Using in situ X-ray absorption spectroscopy at the O K-edge and density functional theory calculations, it is found that such bridging O2– has a lower antibonding orbital energy and thus weaker Cu–O/Fe–O strength. In selective NH3 oxidation, the weak Cu–O/Fe–O bond enables fast Cu redox for NH3 conversion and direct NO adsorption via Cu–O–NO to promote N–N coupling toward N2. As a result, 99% N2 selectivity at 100% conversion is achieved at 573 K, exceeding most of the reported results. This result suggests the importance to design, determine, and utilize the unique features of bridging O2– in catalysis