Demonstration of acousto-optical modulation based on a thin-film AlScN photonic platform

Acousto-optic(AO)modulation technology holds significant promise for applications in microwave and optical signal processing.Thin-film scandium-doped aluminum nitride(AlScN),with excellent piezoelectric properties and a wide transparency window,is a promising candidate for achieving on-chip AO modulation with a fabri-cation process compatible with complementary metal-oxide-semiconductor(CMOS)technology.This study presents,to the best of our knowledge,the first demonstration of AO modulators with surface acoustic wave generation and photonic waveguides monolithically integrated on a 400-nm-thick film of AlScN on an insulator.The intramodal AO modulation is realized based on an AlScN straight waveguide,and the modulation efficiency is significantly enhanced by 12.3 dB through the extension of the AO interaction length and the utilization of bidirectional acoustic energy.The intermodal AO modulation and non-reciprocity are further demonstrated based on a multi-mode spiral waveguide,achieving a high non-reciprocal contrast(>10 dB)across an optical bandwidth of 0.48 nm.This research marks a significant stride forward,representing an advancement in the realization of microwave photonic filters,magnet-free isolators,and circulators based on the thin-film AlScN photonic platform.

Silicon substrate-integrated hollow waveguide for miniaturized optical gas sensing

Gas sensors have a wide variety of applications.Among various existing gas sensing technologies,optical gas sensors have outstanding advantages.The development of the Internet of Things and consumer electronics has put stringent requirements on miniaturized gas sensing technology.Here,we demonstrate a chip-scale silicon substrate-integrated hollow waveguide(Si-iHWG) to serve as an optical channel and gas cell in an optical gas sensor.It is fabricated through silicon wafer etching and wafer bonding.The Si-i HWG chip is further assembled with an off-chip light source and detector to build a fully functional compact nondispersive infrared(NDIR) CO_(2) sensor.The chip size is 10 mm × 9 mm,and the dimension of the sensor excluding the microcontroller board is 50 mm × 25 mm × 16 mm.This chip solution with compactness,versatility,robustness,and low cost provides a cost-effective platform for miniaturized optical sensing applications ranging from air quality monitoring to con-sumer electronics.