Real-Time Measurements of Photonic Microchips with Femtometer-Scale Spectral Precision and Ultra-High Sensitivity

TL;DR

The paper introduces SOHO, a novel real-time measurement technique for photonic microchips that offers femtometer-scale spectral resolution and ultra-high sensitivity, surpassing traditional methods in speed and precision.

Contribution

We present SOHO, a simple, high-performance measurement method that achieves real-time operation with significantly improved spectral resolution and sensitivity for photonic integrated circuits.

Findings

Achieved 19.1 femtometers spectral resolution experimentally.

Demonstrated over 30 dB higher sensitivity than traditional methods.

Validated performance on ultrahigh-Q fiber-loop and microresonators.

Abstract

Photonic integrated circuits (PICs) are enabling major breakthroughs in a number of areas, including quantum computing, neuromorphic processors, wearable devices, and more. Nevertheless, existing PIC measurement methods lack the spectral precision, speed, and sensitivity required for refining current applications and exploring new frontiers such as point-of-care or wearable biosensors. Here, we present the Sweeping Optical Frequency Mixing Method (SOHO), surpassing traditional PIC measurement methods with real-time operation, 30 dB higher sensitivity, and over 100 times better spectral resolution. Leveraging the frequency mixing process with a sweeping laser and custom control software, SOHO excels in simplicity, eliminating the need for advanced optical components and additional calibration procedures. We showcase its superior performance on ultrahigh-quality factor (Q) fiber-loop resonators (Q = 46M) as well as microresonators realized on a new optical waveguide platform. An experimental spectral resolution of 19.1 femtometers is demonstrated using an 85-meter-long unbalanced fiber Mach Zehnder Interferometer, constrained by noise resulting from the extended fiber length, while the theoretical resolution is calculated to be 6.2 femtometers, limited by the linewidth of the reference laser. With its excellent performance metrics, SOHO has the potential to become a vital measurement tool in photonics, excelling in high-speed and high-resolution measurements of weak optical signals.