A single-mode fiber with plano-convex silicon microlens is proposed for butt-coupling between single-mode fibers and high-index-contrast waveguides with fine mode-field diameter. The lensed fiber has two specific features, high focusing power, and null working distance. The theoretical focus-spot diameter at the endface of the lensed fiber is calculated to be as small as 0.56 microm at a wavelength 1.55 microm. A simple fabrication method for the lensed fiber employing chemical etching and rf-sputtering is presented. Experiments showed that the mode-field-diameter of a single-mode fiber was successfully contracted from 10.5 to 1.3 microm with the lensed fiber.
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http://dx.doi.org/10.1364/ao.47.006345 | DOI Listing |
J Biophotonics
January 2025
Laser Biomedical Applications Division, Raja Ramanna Centre for Advanced Technology, Indore, India.
Availability of a suitable tool for carrying out non-invasive measurement of Raman signatures in situ, from biological tissues having low Raman cross section is a clinically unmet need faced with manifold challenges. A Raman probe can prove to be an invaluable component of clinical Raman diagnostic systems. We present development of a Raman probe capable of measuring artefact free Raman spectra of biological tissues in situ.
View Article and Find Full Text PDFUltra short pulse Ti:sapphire lasers, crucial for most demanding applications, have traditionally been complex and costly due to their pump sources. GaN-based laser diodes offer new prospects for pumping, yet challenges persist in achieving sufficient Ti:sapphire output power and beam quality. We introduce what we believe to be a novel approach using pulsed blue laser diode pumping of a Ti:sapphire amplifier.
View Article and Find Full Text PDFWe proposed a label-free method for the identification and classification of atherosclerosis plaques by combining optical coherence tomography (OCT) with ultraviolet autofluorescence spectroscopy (uFLS). By aligning the OCT source and the FLS excitation beams, we were able to illuminate the same spot on plaques fixed to the integrated probe, which underwent rotational scanning. This setup enabled the detection of both OCT images and uFLS spectra of the plaques in a co-localized manner.
View Article and Find Full Text PDFLight Sci Appl
September 2024
Department of Applied Physics, The Hong Kong Polytechnic University, 999077, Hong Kong, China.
Natural selection has driven arthropods to evolve fantastic natural compound eyes (NCEs) with a unique anatomical structure, providing a promising blueprint for artificial compound eyes (ACEs) to achieve static and dynamic perceptions in complex environments. Specifically, each NCE utilises an array of ommatidia, the imaging units, distributed on a curved surface to enable abundant merits. This has inspired the development of many ACEs using various microlens arrays, but the reported ACEs have limited performances in static imaging and motion detection.
View Article and Find Full Text PDFThe impact of thermal lensing (TL) on the transverse mode instability (TMI) threshold power in rod-type fiber amplifiers is investigated. Simulations are conducted with a 3D coupled mode analysis on a set of five scaled large pitch fiber (LPF) amplifiers. The LPF fibers are represented by surrogate step-index fibers (SIFs) with scaled cladding diameters, core diameters, and numerical apertures for a fixed normalized frequency V equal to 3.
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