Bias-Aware Detection Limits, Calibration Transfer and Matched-Control Robustness in Dual-Parameter Photonic Refractive-Index and Temperature Sensing: A Coupled Interface-Mode Multilayer Case Study

Dual-parameter photonic sensors often report a single detection limit without specifying its statistical definition or calibration transferability. This fully computational study evaluates these issues in a coupled interface-mode multilayer for simultaneous refractive-index (RI) and temperature sensing. The two resonances occur at 1517 and 1651 nm, with loaded Q factors of 232 and 208 and RI sensitivities of 90.71 and 329.41 nm/RIU. Modal-overlap analysis links the sensitivity matrix to distinct thermal-to-index response ratios. Bounded nonlinear calibration yields held-out errors of 2.43 × 10⁻⁵ RIU and 0.155°C. At 1% false alarm and 95% detection, device-specific probability-of-detection limits are 4.36 × 10⁻⁵ RIU and 0.123°C; transferring one nominal calibration across devices worsens them by factors of 81 and 203 under the linewidth-limited repeatability model. A sensitivity-matched trivial control gives statistically equivalent yield within the declared margin, bounding the topological claim to the studied operating point. Structural audits further show that the sensing modes are cavity-selected, the nanolaminate provides no net measured performance benefit, and hyperbolicity is unobservable at normal incidence. The results support bias-aware detection and calibration-transfer analysis as more informative benchmarks than nominal sensitivity alone.