Intrinsic Spectrum Analysis of Laser Dynamics Based on Fractional Fourier Transform

TL;DR

This paper introduces a novel fractional Fourier transform-based method for analyzing the intrinsic spectrum of high-speed, wavelength-swept lasers, enabling better characterization of laser dynamics for precision measurement.

Contribution

It proposes a new fractional Fourier transform approach to analyze laser intrinsic spectra during fast wavelength sweeping, improving understanding of laser energy distribution.

Findings

Effective analysis of laser intrinsic spectrum at high scanning speeds

Identification of optimal measurement window for narrowest spectrum

Enhanced understanding of laser dynamical parameters

Abstract

Intrinsic spectrum that results from the coupling of spontaneous emission in a laser cavity, can determine the energy concentration and coherence of lasers, which is crucial for the optical high-precision measurement. Up to now, it is hard to analyze the intrinsic spectrum in the high-speed laser dynamics process, especially under the condition of fast wavelength sweeping. In this work, a new method to analyze the laser intrinsic spectrum is proposed with the laser energy decomposition to a series of chirp-frequency signals, which is realized by fractional Fourier transform (FRFT) of the coherently reconstructed laser waveform. The new understanding of the energy distribution of lasers contributes to the accurate characterization of laser dynamical parameters in time-frequency domain. In the proof-of-concept experiment, the time-frequency dynamical process of a commercial wavelength swept laser is tested with different wavelength-scanning speeds, and the most suitable measurement time window width required for the FRFT-based narrowest spectrum is also explored. The proposed analysis method of laser dynamical parameters will promote the understanding of laser dynamics, and benefit for the optical precision measurement applications.