Lately, yellow lasers have been showing promising results for the treatment of diabetic retinopathy. In this study, a numerical model for Dy-doped yellow fiber lasers has been developed to analyze the impact of the most significant input parameters. The impact of input pump power, cavity length, and reflectivities of the mirrors on the output signal power has been studied, by evaluating the impact of the lifetime of Dy-energy levels. Additionally, an investigation of excited state absorption has been conducted. Simulation results provide valuable insights into both the qualitative and quantitative influence of these input parameters on the performance and efficiency of Dy-doped fiber lasers for yellow emission.
The paper presents the design and preliminary experimental validation of a fiber laser with direct emission in the yellow. The active material is a Dy-doped custom-made phosphate fiber, which is pumped by high-power blue diode lasers emitting at 450 nm. A suitable model has been developed to optimize the laser behavior and validated with a low-power version of the laser cavity with femtosecond written Bragg grating mirrors.
In this work, we present an ultra-high sensitivity (S) refractive index (RI) sensor for biological applications. Silicon on insulator (SOI) ring resonator (RR) based RI sensors have been extensively investigated. Light propagation is studied in the small SOI RRs based on sub-wavelength grating (SWG) waveguides with aqueous claddings. For the device analysis, the two-dimensional conformal transformation method is jointly used with the effective index method. Furthermore, FEM simulations of this structure have been also performed in both the air and water claddings. These good-matched results are further compared with experimental and FDTD results in other valid references. Having found a high data matching between our results and experimental results, we repeat our calculation for different side-widths (d=150-225 nm) and ring radii (7-10 µm). For each ring radius, the best amount of side-width is found. Then bulk refractive index sensing experiments are simulated using changing cladding RI in the range of nc=1.332-1.350 RIU. These RI changes correspond to concertation changes of glucose-water solutions in the cladding. Finally, we obtain the highest sensitivity of 24946 nm/RIU in the case of a radius 7 µm, 500 nm width, 220 nm height, 150 nm side-width, and T of 50 nm between the grating arrays on the RR. It is worth noting that this proposed structure shows 150 times sensitivity enhancement compared to a standard SOI RR-based biosensor with the same radius, w, and h. In addition, the RI sensor suggested in this work shows ultra-high sensitivity in a dynamic range of 1.332-1.352 RIU. This range of RI variation covers almost all the RI variations of the blood components. These results show excellent potential for employing the proposed SOI RR based on SWG waveguides in a liquid-biopsy analysis of patients with cancer. These might pave the way toward the early detection of cancers.
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