Unravelling temporal dynamics in integrating cavities from nonuniform to uniform light fields

In this study, we investigate the light propagation characteristics within an integrating cavity, focusing on the transition from a non-uniform light field (NULF) to a uniform light field (ULF). We challenge the conventional assumption in integrating cavity theory that postulates the immediate establishment of a ULF upon light entry. Employing both experimental and simulation approaches, we derive the time constant of the integrating cavity under ULF conditions and measure the cavity’s transient and steady-state responses. Our findings reveal that while a brief NULF phase precedes the ULF, the total radiant flux within the cavity adheres to the ULF propagation law from the onset. This study demonstrates that the NULF can be treated as an approximation of the ULF in terms of total radiant flux variation within an integrating cavity. Our study not only provides empirical validation for integrating cavity theories based on the ULF assumption but also presents compelling evidence of their efficacy in cavities with diverse geometries.