Quantum dot emission enhancement via coupling with an epsilon-near-zero sublayer

Quantum emitters operating at telecom wavelengths are essential for the advancement of quantum technologies, particularly for the development of integrated on-chip devices for quantum computing, communication, and sensing. Coupling resonant structures to an epsilon-near-zero (ENZ) environment has been shown to enhance their optical performance by both increasing spontaneous emission rates and improving emission directionality. In this work, we comparatively study the emission characteristics of colloidal PbS/CdS (core/shell) quantum dots at telecom wavelengths on different substrates. Two different sets of quantum dots, emitting within and outside the epsilon-near-zero region, are deposited on both glass and indium tin oxide (ITO) substrates. Our results demonstrate that coupling quantum dots to the ENZ spectral region results in a reduction in photoluminescence lifetime of 54 times, a 7.5-fold increase in saturation intensity, and a relative emission cone narrowing from 17.6° to 10.3°. These results underline the strong dependence of quantum dot emission properties on the spectral overlap with the epsilon-near-zero condition, highlighting the potential of transparent conducting oxides, such as ITO, for integration into next-generation quantum photonic devices. Owing to their CMOS compatibility, fabrication tunability, and high thermal and optical damage thresholds, these ENZ materials offer a robust platform for scalable and high-performance quantum optical systems operating within the telecom bandwidth.