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Optical-feedback (OF) cavity ring-down spectroscopy consisting of a linear cavity is developed by employing a continuous wave laser diode (LD) with multi-longitudinal modes. Due to the OF effect caused by the cavity output laser back into the LD, the laser frequency is locked, and the intracavity laser intensity is enhanced. We use different concentrations of gases to test the apparatus, and the results show good agreement with theoretical values. Owing to the compactness of the laser source and high detection accuracy, the device can be used for detection of low-concentration absorbent gases in the environmental monitoring field.
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http://dx.doi.org/10.1364/AO.450874 | DOI Listing |
Sensors (Basel)
July 2025
Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China.
An external power build-up cavity of a line-narrowed 407-nm laser diode for Raman gas analysis was demonstrated to possess good gas detection capabilities. By employing an ordinary laser diode without anti-reflection coating or and a bandpass interference filter in an external cavity resonance, the laser linewidth was narrowed by resonant optical feedback, and tens of watts of external cavity power were built up. The coupling mechanism between the semiconductor laser and the external cavity are discussed, as well as the noise background in the experimental results.
View Article and Find Full Text PDFA standard method to reduce the linewidth of semiconductor lasers involves the use of external optical feedback (EOF). However, feedback powers less than 1 % usually trigger coherence collapse (CC), leading to chaotic laser dynamics and linewidth broadening. This paper explores a method to mitigate CC through precise tuning of the feedback polarization depending on the feedback power.
View Article and Find Full Text PDFVertical-cavity surface-emitting laser (VCSEL) has received much attention due to its high modulation response bandwidth, two linear polarization modes, and easy integration. The fundamental characteristics of lasers can be observed by simple optical feedback. Here, we experimentally investigate the dynamical characteristics in a 1550-nm VCSEL subjected to mirror optical feedback.
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February 2025
Mid-infrared (mid-IR) fiber lasers have faced significant challenges in achieving all-fiberized structure with high efficiency and high output power due to the limitations of conventional cavity designs. In this paper, we introduce what we believe to be a novel 2.8 µm all-fiber laser configuration with a low optical feedback linear cavity, effectively eliminating the need for traditional high-reflector components.
View Article and Find Full Text PDFA flexible random laser with switchable modes and directional emission will advance the application of random lasers in high-quality light sources and photonic integration. In this paper, a fiber-shaped random laser based on phase transition hydrogel is proposed. The change of phase states in hydrogel affects the light scattering and optical feedback path, enabling the reversible switching of lasing mode between incoherent and coherent random lasing.
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