Mechanism of desorption-laser suppression of rubidium-induced PIC waveguide loss

Determine whether the suppression of rubidium-induced propagation loss in silicon nitride photonic integrated circuit waveguides, achieved by injecting a counter-propagating 801 nm desorption laser while operating a rubidium pill dispenser in a microfabricated borosilicate vapor cell, is caused by material heating, light-induced atomic desorption (LIAD), or a combination of both, and quantitatively characterize the physical mechanism by which the desorption laser prevents rubidium adsorption and waveguide degradation.

Background

The study demonstrates that standard high-power activation of a rubidium pill dispenser severely degrades air-clad silicon nitride waveguides in integrated vapor–PIC devices. To avoid this, the authors develop a low-power, pulsed activation protocol and introduce a counter-propagating 801 nm desorption laser through the waveguide, which effectively suppresses rubidium-induced propagation losses and enables waveguide-based rubidium spectroscopy.

While prior work in related platforms attributes alkali desorption to either material heating or light-induced atomic desorption (LIAD), the present experiments do not identify the dominant mechanism in this integrated PIC context. Clarifying the mechanism would inform optimal desorption wavelengths, power budgets, and device designs for robust operation across applications in quantum optics and sensing.