Abstract:
Background Visible lasers in the 560-600 nm band are widely used in vascular disease treatment. Conventional solid-state lasers for this band feature complex systems and high costs, which limit their application in low-resource medical scenarios. Organic solid-state dye lasers offer low-cost solution processing and wide spectral tunability, making them promising alternatives for disposable medical light sources.
Purpose This study aims to develop a simple, low-cost, and easily replaceable vertical external-cavity surface-emitting laser based on an organic dye-doped polymer film, and to evaluate its lasing performance under nanosecond and femtosecond pumping conditions.
Methods A Rhodamine 6G-doped poly(methyl methacrylate) (Rh6G-PMMA) gain film was fabricated via solution casting, and the gain film was physically placed inside a planar-planar external cavity formed by a dichroic input mirror and a broadband high reflector. Lasing characteristics, including threshold, spectral linewidth, output stability and operational lifetime, were measured under 532 nm nanosecond and 515 nm femtosecond pumping.
Results The device achieved stable laser output at a central wavelength of approximately 562 nm under both pumping schemes. The lasing thresholds were 2.12 mJ/cm2 and 4.93 mJ/cm2 for nanosecond and femtosecond pumping, respectively, with the full width at half maximum (FWHM) of the output spectrum narrowing to 4.7 nm and 2.2 nm. Under femtosecond pumping at 6.09 mJ/cm2, the device could operate stably for over 2300 laser pulses.
Conclusions The vertical external-cavity surface-emitting organic dye film laser features a very simple structure, low fabrication cost, and a physically separable gain film that can be quickly replaced after performance degradation. These characteristics make it a promising candidate for low-cost, disposable gain modules in biomedical applications such as vascular lesion treatment.
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