Vol. 17 No. 2 (2025)

This issue of Photonics Letters of Poland presents a diverse collection of photonics research, spanning holography, spectroscopy, fiber-optic sensing, and environmental monitoring. Each contribution presents innovative approaches to solving real-world challenges using advanced photonic technologies. Specifically: (i) A comparative study of phase-only hologram encoding methods reveals that Direct Phase-only Holograms (D-PoH) offer the best performance for wide-angle displays. The paper also proposes improvements to the Complex Amplitude Modulation (CAM) method to address its limitations in brightness and image quality. (ii) Raman spectroscopy, supported by SEM imaging, is used to analyze and identify the composition and morphology of unknown human kidney stones. This non-invasive technique demonstrates strong potential for clinical diagnostics and personalized treatment planning. (iii) Investigations on microplastic emissions from nail styling materials, identifying particles with allergenic and potentially harmful properties, is presented. The findings underscore the need for exposure assessments and emission control strategies in enclosed environments like beauty salons. (iv) A PVDF-coated Fabry–Pérot fiber-optic sensor is introduced for detecting PFAS in water, showing reversible spectral shifts and high repeatability. Its low cost and portability make it ideal for in situ environmental monitoring. (v) The spatial modulation of the pump beam enabling lasing in cholesteric liquid crystal layers is also presented. It also shows the feasibility of dynamic optical data recording on thin laser-active layers. (vi) A hollow-core photonic crystal fiber sensor combined with deep learning achieving 96.3% accuracy in detecting lung cancer from exhaled breath is shown. This approach offers a promising path toward portable, non-invasive early diagnostic tools. (vii) A V-grooved, gold-coated photonic crystal fiber sensor operating in the NIR range exhibiting exceptional sensitivity and resolution for tumor detection is studied. Its optimized design ensures minimal loss and high efficiency in distinguishing healthy from cancerous tissues. (viii) Theoretical modeling of a graphene light source integrated with a silicon membrane reveals its potential as a miniaturized, tunable IR emitter. The study explores spectral tuning capabilities based on membrane deflection and device geometry.