Excitation polarization sensitive enhancement of spin defects emission in hexagonal boron nitride with artificially induced wrinkles

Hexagonal boron nitride (hBN) with optically active spin defects has recently garnered interest as a promising platform to explore room temperature quantum information processing and sensing. Previously, various methods, such as plasmonic resonance and strain, have been employed to manipulate the emission properties of such spin defects. In this work, wrinkles have been induced on exfoliated, He+ ion irradiated hBN flakes by transferring them onto pre-stretched PDMS, which is subsequently relaxed. Photoluminescence (PL) of hBN spin defects in the flakes is observed to be enhanced up to 20-fold at the wrinkles. Moreover, the enhancement of PL is two and a half times larger when the linear polarization of the laser source aligns with the direction of the wrinkle compared to the case when it aligns perpendicular to the wrinkle. The strong coupling of wrinkle geometry to PL enhancement points to cavity effects as its origin. Strain alone is ruled out as the underlying cause of PL amplification in the wrinkles through Raman spectroscopy and optically-detected magnetic resonance (ODMR) studies. Our investigated structures have even further potential to advance quantum information and sensing application of spin defects in hBN if they are coupled with other means of amplification, such as surface plasmons.