分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Precise measurement of multi-parameters of ultrafast lasers is vital both in scientific investigations and technical applications, such as, optical field manipulation, pulse shaping, sample characteristics test, and biomedical imaging. Tremendous progress in parameter measurement of ultrafast laser has been made, including single-shot spectra acquired by time-stretch dispersive Fourier transform in spectral domain, and pulse magnification or compression realized by time lens in temporal domain. Nevertheless, single-shot measurement of frequency-resolved states of polarization (SOPs) of ultrafast lasers has not been reported so far, and the unregular SOP evolution dynamics in ultrafast pulses is hardly explored. Here, we demonstrate a new single-shot frequency-resolved SOPs measurement system by utilizing division-of-amplitude method under far-field approximation. Large dispersion is utilized to time-stretch the laser pulses, where the spectrum information is mapped into temporal waveform via dispersive Fourier transform. By calibrating system matrix with different wavelengths, the precise frequency-resolved SOPs are obtained together with high speed opto-electron detection. We demonstrate applications in direct measurement of transient mode-locked fiber laser dynamics. We observe complex frequency-dependent SOPs dynamics in the building up of dissipative solitons, and apparent discrepancy of SOPs between sideband and main peak in conventional solitons. Our observations reveal that the SOP plays a far more complex part in mode-locking process, which is different from the traditional viewpoint. Taking advantage of broadband achromatic optical elements, this method can be extended to measurement of much broad pulse lasers, which will pave the way for reliable measurement and precise control of ultrafast lasers with frequency-resolved SOPs structures.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Ligang Huang
Tianyi Lan
Chaoze Zhang
Laiyang Dang
Tianyu Guan
Bowen Zheng
Shunli Liu
Lei Gao
Wei Huang
Guolu Yin
Tao Zhu
摘要： 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.
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