MoO 3 /MgF 2 Distributed Bragg Reflectors for Colloidal Quantum Dot-Based Planar Microcavities

Planar optical microcavities based on distributed Bragg reflectors (DBRs) are key components of integrated photonics.Because the active layer is sandwiched between the top and bottom DBRs, the fabrication of a low-damage top mirror is particularly important to minimize plasmaor thermally induced degradation of the active material.Here, we demonstrate a thermally evaporated MoO 3 /MgF 2 DBR as a low-damage top mirror for planar microcavities.Spectroscopic ellipsometry was used to determine the dispersive optical constants of MgF 2 and MoO 3 , modeled using Cauchy and Tauc-Lorentz models, respectively.These parameters enabled transfer-matrix-based DBR design with a stopband centered at 560 nm.By employing a low deposition rate of ~0.2 Å/s to reduce film stress, MoO 3 /MgF 2 multilayers with thicknesses close to quarter-wave targets were fabricated, achieving approximately 90 % reflectance and a stopband width of about 260 nm for a 4-pair DBR.Integration with a sputtered SiO 2 /Ti 3 O 5 bottom DBR and a spin-coated InP/ZnS colloidal quantum dot active layer produced a planar microcavity that narrowed the emission linewidth from 35 to 3 nm and exhibited parabolic angle-resolved photon dispersions with effective indices near 2.0.These results demonstrate the feasibility of MoO 3 /MgF 2 DBRs as promising low-damage top mirrors for solution-processed microcavity devices.