Polymer waveguide Mach-Zehnder interferometer coated with dipolar polycarbonate for on-chip nitroaromatics detection

•A dipolar polycarbonate with side-chain donor-acceptor chromophores was synthesized and utilized for explosive detection.•The waveguide Mach-Zehnder interferometer (MZI) was facilely fabricated with dipolar polycarbonate for on-chip explosive vapor sensing.•Nitrobenzene vapor can be instantly sensed (response time <100 s) and it makes the interference fringes shift of more than 8 nm until saturated absorption.•DNT vapor at lower concentration (ppb level) can be rapidly (response time <100 s) and sensitively detected (interference fringes shift >6 nm).