FDTD-based design and optimization of multilayer cavity structures for efficient telecom-band single-photon sources

Single-photon sources (SPSs) that employ semiconductor quantum dots (QDs) are of increasing interest for quantum communication and information technologies, particularly at telecom wavelengths where fiber transmission losses are minimal. In this study, we carry out a systematic optical analysis of nanocavity structures designed for enhancing QD emission. Three-dimensional finite-difference time-domain (FDTD) simulations were employed to evaluate cavity reflectivity spectra, resonant modes, quality factors, and photon collection efficiencies. The role of semiconductor choice was studied by comparing GaAs, InP, and InGaAsP cavities. The results show that GaAs exhibit a red-shifted resonance (~1240 nm), while InGaAsP and InP resonate near 1170 nm. InGaAsP provided the sharpest resonance features and the highest photon collection efficiency (~45.7 %), compared to GaAs (~17.7 %) and InP (-13.0 %). Additional analyses of oxide spacer layers and cavity geometries further highlight how refractive index contrast and dielectric design govern resonance stability and outcoupling performance. The findings provide a study- oriented framework for optimizing cavity-emitter systems and form a reference for guiding future single-photon source design in fiber-compatible quantum networks.