The Jiangmen Underground Neutrino Observatory (JUNO) has successfully completed filling its 20,000-tons liquid scintillator detector and begun data taking on Aug. 26. After more than a decade of preparation and construction, JUNO is the first of a new generation of very large neutrino experiments to reach this stage. Initial trial operation and data taking show that key performance indicators met or exceeded design expectations, enabling JUNO to tackle one of this decade’s major open questions in particle physics: the ordering of neutrino masses—whether the third mass state (ν₃) is heavier than the second (ν₂).

Compact and efficient optical frequency combs are critical for modern technologies like spectroscopy, metrology, and communications. Researchers at Harvard have developed a hybrid Kerr-electro-optic frequency comb on thin-film lithium niobate that achieves both ultra-broad spectral span (75.9 THz) and fine microwave-rate line spacing (29.3 GHz). This integrated solution overcomes a longstanding spacing-span trade-off, paving the way for scalable, chip-based frequency references that may find use in a wide range of advanced application settings.

Polygonal optical vortices uniquely enable numerous applications due to the new degrees of freedom and their customizable light intensity structure. Previous demonstrations have been limited to continuous-wave regimes. In order to generate femtosecond polygonal optical vortices (FPOVs), scientists in China invented a mode locked solid-state Yb:KGW oscillator with a semiconductor saturable absorber mirror working at quasi-frequency-degenerate state to deliver the square, pentagonal, and hexagonal shapes FPOVs.