| Temporal spectroscopy is an ultrafast spectroscopy method that maps the spectral information to the time domain and then combines with large-bandwidth temporal acquisition.By taking the high-speed advantage of detection devices,it can get tens of millions of spectra per second,which is important for the study of transient phenomena.The temporal spectrometers are mainly divided into two categories: the time-stretch spectrometer which is based on dispersive Fourier transform and the time-focusing spectrometer which is based on time lens.The time-stretch spectrometer has a simple setup,but it is only suitable for observing the absorption spectrum of the pulse.The time-focusing spectrometer can ananlyze any spectrum with a high sensitivity and spectral resolution,but the setup is complex and it has a limited observation bandwidth.In this thesis,the two temporal spectrometers are analyzed in theory and experiment.The performance of the temporal spectrum analyzers are optimized,and a series of application researches on rapid process monitoring are carried out.The innovative achievements of the thesis mainly include the following aspects:(1)The theoretical model of temporal spectroscopy is improved.The theoretical models of the time-stretch spectrometer and time-focusing spectrometer are analyzed.The distortion theory analysis model of the temporal spectroscopy is improved.The effects of the third-order dispersion on the time-stretch and time-focusing spectrometers are analyzed,respectively.The methods to eliminate the third-order dispersion are explored.(2)A time-stretch spectrometer with a high temporal sampling resolution is designed and implemented.By combining the dual comb pump-probe technology with the time-stretch spectrometer,a time-stretch spectrometer with a high temporal sampling resolution is realized.It enabled the sampling resolution of the spectrum to be increased from the order of ns to the order of sub-ps.The carrier dynamics of the semiconductor optical amplification is further studied,and the spectral evolution in the window of 10 ns is plotted with a time interval of 592.5 fs.The wavelength-dependent carrier recovery overshoot is observed.(3)The frequency Bloch oscillations is designed and implemented,and the real-time observation is carried out with the time-stretch spectrometer.By introducing phase modulation in the fiber loop,a frequency lattice is constructed.It can be analogous to the Bloch oscillations of the electron in the spatial lattice,and realize the Bloch oscillations in the optical frequency domain.The time-stretch spectrometer is used to monitor the spectral evolution in the Bloch oscillations process in real time: when a short pulse is incident,the spectrum presents an overall oscillating behavior;when a wide pulse is incident,the spectrum presents a breathing oscillating behavior.(4)The design realizes a large-bandwidth time-focusing spectrometer that can cover the C and L bands at the same time.The elimination of the third-order dispersion of the post-dispersion module enables the system to meet the dispersion matching relationship in a large bandwidth range.By introducing the time-division multiplexing technology into the time-focusing spectrometer,the spectrum of the C and L band signals can be obtained separately in adjacent periods.The observation bandwidth has been increased to 58 nm,with a frame rate of 10 MHz and a resolution of 20 pm.(5)A time-focusing spectrometer with a high spectral resolution is designed and implemented.The elimination of the third-order dispersion allows a large time lens window,which improves the optical resolution of the system.The dual-comb asynchronous optical sampling technology improves the electrical resolution of the sysytem.As a result,the resolution of the time-focusing spectrometer has been increased from 20 pm to 1 pm.Based on this,the lasing spectrum dynamics of the erbium-doped fiber amplifier and the thermal drift dynamics of the microring resonance peak are measured. |
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