Low-Energy, Octave-Spanning Supercontinuum Generation in Ta_2O_5 Waveguides: Towards Optical Coherence Metrology

Abstract

Supercontinuum generation (SCG) on integrated photonic platforms is a pivotal technology for developing next-generation chip-scale systems for precision spectroscopy and metrology. While significant progress has been made with silicon (Si) and silicon nitride ($Si_3N_4$) platforms, they are often constrained by two-photon absorption (TPA) or moderate nonlinear coefficients, necessitating a trade-off between energy efficiency and bandwidth. Tantalum pentoxide ($Ta_2O_5$), possessing both high nonlinearity and a wide bandgap, emerges as a promising candidate; however, current implementations remain challenged by high pump energy consumption. Here, we report a low-loss $Ta_2O_5$ integrated waveguide fabricated via the Damascene process. It enables the generation of a two-octave-spanning spectrum with a low pulse energy of only 92.9 pJ (60 fs, 1550 nm). Notably, the corresponding peak power is a mere 1.36 kW, which is nearly an order of magnitude lower than that of state-of-the-art comparable broadband sources. Furthermore, at the maximum pump energy, our spectrum exhibits an ultrabroad coverage from 450 nm to 3400 nm, spanning nearly three octaves. Supported by numerical simulations, we analyze the dynamics of soliton fission. Furthermore, a Michelson interferometry system developed using this source exhibits superior performance, achieving not only micrometer-scale axial resolution but also a 6 dB sensitivity roll-off length of 3.1 mm. This exceptional roll-off performance, combined with a displacement measurement sensitivity of 346 nm, underscores the immense potential of the $Ta_2O_5$ platform for applications in biomedical imaging and precision metrology.