Ultralow-Threshold Lithium Niobate Photonic Crystal Nanocavity Laser

Thin film lithium niobate (TFLN) has emerged as a promising platform for modern complete photonic integrated circuits due to its exceptional optical properties. The development of rare-earth-ion-doped TFLN has led to significant advancements in on-chip microlasers. However, challenges persist in developing energy-efficient, low-threshold lasers on TFLN. In this letter, we report a heterostructure photonic crystal (PhC) nanobeam cavity with a Purcell factor (∼2.4 × 10⁴ μm^-3) and β factor (∼0.23) both enhanced by 2 orders of magnitude compared to whispering gallery mode (WGM) lasers. The first demonstration of the single-mode integrated LN PhC laser is presented, achieving a record-low lasing threshold (1.19 μW) on the erbium-doped TFLN platform, attributed to the enhanced Purcell factor and β factor. The effect of the Purcell and the β factor on ultralow-threshold lasing has been studied in LN PhC lasers, which contributes to the development of low-power TFLN integrated photonics.