Zhongjin Lin

2 months ago | nature.com | X. Yao |Yulong Yang |Xiaosong Ma |Zhongjin Lin |Yuntao Zhu |Wei Ke | +3 more

Real-time measurement of optical frequency variations (OFVs) is crucial for various applications including laser frequency control, optical computing, and optical sensing. Traditional devices, though accurate, are often too large, slow, and costly. Here we present a photonic integrated circuit (PIC) chip, utilizing the sine-cosine encoder principle, for high-speed and high-resolution real-time OFV measurement. Fabricated on a thin film lithium niobate (TFLN) platform, this chip-sized optical frequency detector (OFD) (5.5 mm × 2.7 mm) achieves a speed of up to 2500 THz/s and a resolution as fine as 2 MHz over a range exceeding 160 nm. Our robust algorithm overcomes the device imperfections and ensures precise quantification of OFV parameters. As a practical demonstration, the PIC OFD surpasses existing fiber Bragg grating (FBG) interrogators in sensitivity and speed for strain and vibration measurements. This work opens new avenues for on-chip OFV detection and offers significant potential for diverse applications involving OFV measurement. The authors showcase a photonic integrated circuit chip for fast optical frequency variation measurement, fabricated with thin-film lithium niobate, with a size of 5.5 mm × 2.7 mm, a speed up to 2500 THz/s, a resolution of 2 MHz, and a range of 160 nm.