Single-shot wavelength meter on a chip based on exponentially increasing delays and in-phase quadrature detection

A solid-state wavelength measuring instrument based on a SiO₂ photonics platform is presented. The chip-scale wavemeter device has no moving parts and allows instantaneous wavelength measurement with high precision and accuracy 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. Design of the MMI couplers is supported by simulations using the Finite-Difference Time-Domain (FDTD) method. A hydrogen fluoride gas cell is used in conjunction with the chip-scale wavemeter to determine the wavelength relative to traceable absorption lines. This approach does not rely on knowledge of the effective or group refractive indices to estimate wavelength. The fabrication, experimental evaluation and calibration of the device are discussed. Observed performance indicates a spectral support of 37.378 nm (i.e., frequency bandwidth 6.608 THz), with a resolution of 6.1 pm (1.1 GHz) at 1σ, corresponding to 1 part in 6,127.