Single-shot wavelength meter on a photonic chip for absolute distance measurement using frequency scanning interferometry

A chip-scale solid-state wavelength measuring device based on a silicon photonics platform is presented. It has no moving parts and allows single-shot wavelength measurement with high precision over a nominal bandwidth of 40 nm in the O-band. The wavemeter design is based on multimode interferometer (MMI) couplers and a multi-band Mach–Zehnder interferometer (MZI) structure with exponentially increasing optical path differences and in-phase quadrature detection. The design of the MMI couplers is supported by simulations using the Finite-Difference Time-Domain (FDTD) method. The design, experimental evaluation, and calibration of the device are discussed. Observed performance indicates a spectral support of 38.069 nm (i.e., frequency bandwidth 6.608 THz), with a resolution of 8.3 pm (1σ), corresponding to 1 part in 4,587. This wavelength meter approach has emerged from a need in absolute distance measurements using frequency scanning interferometry, where knowledge of the instantaneous wavelength of a tunable laser is required to relate signal frequency with target range. We also present an adaptive delay line on a chip, demonstrate its use for range measurements, and suggest how the wavelength meter could evolve for real-time applications.