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Towards visible-wavelength passively mode-locked lasers in all-fibre format
摘要： Mode-locked fibre lasers (MLFLs) are fundamental building blocks of many photonic systems used in industrial, scientific and biomedical applications. To date, 1–2 μm MLFLs have been well developed; however, passively mode-locked fibre lasers in the visible region (380–760 nm) have never been reported. Here, we address this challenge by demonstrating an all-fibre visible-wavelength passively mode-locked picosecond laser at 635 nm. The 635 nm mode-locked laser with an all-fibre figure-eight cavity uses a Pr/Yb codoped ZBLAN fibre as the visible gain medium and a nonlinear amplifying loop mirror as the mode-locking element. First, we theoretically predict and analyse the formation and evolution of 635 nm mode-locked pulses in the dissipative soliton resonance (DSR) regime by solving the Ginzburg-Landau equation. Then, we experimentally demonstrate the stable generation of 635 nm DSR mode-locked pulses with a pulse duration as short as ~96 ps, a radio-frequency signal-to-noise ratio of 67 dB and a narrow spectral bandwidth of <0.1 nm. The experimental results are in excellent agreement with our numerical simulations. In addition, we also observe 635 nm noise-like pulse operation with a wide (>1 nm) and modulated optical spectrum. This work represents an important step towards miniaturized ultrafast fibre lasers in the visible spectral region.
关键词： visible-wavelength,mode-locked fibre lasers,all-fibre format,dissipative soliton resonance,passively mode-locked
更新于2025-09-23 15:19:57
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Silicon photodetector for integrated lithium niobate photonics
摘要： We demonstrate the integration of an amorphous silicon photodetector with a thin film lithium niobate photonic platform operating in the visible wavelength range. We present the details of the design, fabrication, integration, and experimental characterization of this metal-semiconductor-metal photodetector that features a responsivity of 22 mA/W to 37 mA/W over the wide optical bandwidth spanning in the 635 nm–850 nm wavelength range.
关键词： lithium niobate,visible wavelength range,integration,photonics,silicon photodetector
更新于2025-09-12 10:27:22
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Spectroscopic Microtomography in the Visible Wavelength Range
摘要： We demonstrate spectroscopic microtomography in the visible wavelength range (450–700 nm) using digital holographic tomography, a wavelength-scanning source, and a variable-optical-path-length strategy. This multidimensional imaging system can directly measure the absorption-coefficient and refractive-index spectra of a three-dimensional specimen. We apply the system developed to characterize three types of polystyrene beads (undyed, blue dyed, and red dyed) as well as oxygenated and deoxygenated single red blood cells.
关键词： visible wavelength range,absorption-coefficient,digital holographic tomography,refractive-index spectra,spectroscopic microtomography
更新于2025-09-10 09:29:36
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[IEEE 2018 26th European Signal Processing Conference (EUSIPCO) - Roma, Italy (2018.9.3-2018.9.7)] 2018 26th European Signal Processing Conference (EUSIPCO) - Performance Evaluation of N O- Reference Image Quality Metrics for Visible Wavelength Iris Biometric Images
摘要： Image quality assessment plays an important role in iris recognition systems because the system performance is affected by low quality iris images. With the development of electronic color imaging, there are more and more researches about visible wavelength (VW) iris recognition. Compared to the near infrared iris images, using VW iris images acquired under unconstrained imaging conditions is a more challenging task for the iris recognition system. However, the number of quality assessment methods for VW iris images is limited. Therefore, it is interested to investigate whether existing no-reference image quality metrics (IQMs) which are designed for natural images can assess the quality of VW iris images. In this paper, we evaluate the performance of 15 selected no-reference IQMs on VW iris biometrics. The experimental results show that several IQMs can assess iris sample quality according to the system performance.
关键词： image quality assessment,visible wavelength iris,image based attributes,performance evaluation,multi-modality
更新于2025-09-04 15:30:14