On-chip real-time detection of optical frequency variations with ultrahigh resolution using the sine-cosine encoder approach

TL;DR

This paper introduces a compact, high-speed, high-resolution on-chip optical frequency variation detector using a sine-cosine encoder on a lithium niobate platform, outperforming traditional methods in speed and sensitivity.

Contribution

The work presents a novel integrated photonic circuit employing the sine-cosine encoder principle for real-time optical frequency variation detection with unprecedented speed and resolution.

Findings

Achieves 2500 THz/s measurement speed.

Attains 2 MHz resolution over 160 nm range.

Surpasses existing fiber Bragg grating interrogators in sensitivity and speed.

Abstract

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.