Abstract
Comprehensive characterization of ultrafast optical field is critical for ultrashort pulse generation and its application. This paper combines two-step phase-shifting (TSPS) into the spectral phase interferometry for direct electric-field reconstruction (SPIDER) to improve the reconstruction of ultrafast optical-fields. This novel SPIDER can remove experimentally the dc portion occurring in traditional SPIDER method by recording two spectral interferograms with π phase-shifting. As a result, the reconstructed results are much less disturbed by the time delay between the test pulse replicas and the temporal widths of the filter window, thus more reliable. What is more, this SPIDER can work efficiently even the time delay is so small or the measured bandwidth is so narrow that strong overlap happens between the dc and ac portions, which allows it to be able to characterize the test pulses with complicated temporal/spectral structures or narrow bandwidths.
Highlights
Comprehensive characterization of ultrafast optical field is critical for ultrashort pulse generation and its application
The quarter-wave plate (QW) is rotated by 90° in order that the test light reflected back to the QW by a mirror (MI) will be added another πphase-shifting, so the corresponding spectral interferogram to be recorded (I2) becomes
In traditional spectral phase interferometry for direct electric-field reconstruction (SPIDER) algorithms, proper τ is required in order that all the three components are well separated temporally, the recorded spectral interferogram has enough sampling points per fringe in order to suppress the effects of uncorrelated noises which diminish with the square root of the sampling point number[1]
Summary
Comprehensive characterization of ultrafast optical field is critical for ultrashort pulse generation and its application. The reconstructed results are much less disturbed by the time delay between the test pulse replicas and the temporal widths of the filter window, more reliable What is more, this SPIDER can work efficiently even the time delay is so small or the measured bandwidth is so narrow that strong overlap happens between the dc and ac portions, which allows it to be able to characterize the test pulses with complicated temporal/spectral structures or narrow bandwidths. Small τ may lead to the overlapping between the temporal dc and ac portions from the Fourier transform of the recorded spectral interferogram, which may prevent the SPIDER from working correctly Another challenge for SPIDER is to face a test pulse with narrow bandwidth. In SPIDER algorithm, the phase concatenation uses only a subset of the available data or the average of all sets to recover spectral phases[6], which aggravates the insufficiency of the effective sampling points, thereby degrades further the reconstruction quality of the test pulses
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