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Two-step phase-shifting SPIDER

View Article: PubMed Central - PubMed

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.

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The two measured spectral interferograms I1 (black line) and I2 (red line) with π phase-difference (a); /D(t)/ (blue line) and /D(t) − D′(t)/ (black line) (b); the reconstructed temporal intensity and phase profiles with different filter windows: τw = 0.2, 0.3 and 0.4 ps when τ = 0.4 ps (c); and the reconstructed results under the same conditions of (c) except τ = 0.5 ps (d).
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f1: The two measured spectral interferograms I1 (black line) and I2 (red line) with π phase-difference (a); /D(t)/ (blue line) and /D(t) − D′(t)/ (black line) (b); the reconstructed temporal intensity and phase profiles with different filter windows: τw = 0.2, 0.3 and 0.4 ps when τ = 0.4 ps (c); and the reconstructed results under the same conditions of (c) except τ = 0.5 ps (d).

Mentions: Figure 1(a) shows two recorded spectral interferograms (I1 and I2). During recording I1 and I2, the only difference is the test sub-pulse reflected from M1 (see Section Method) has π phase-shifting by rotating the QW with 90°. As predicted, Fig. 1(a) reflects clearly the π phase-difference between the two interferograms. Here, the test pulse is an 800 nm femtosecond pulse train with a bandwidth of 26 nm and the delay τ between the pulse replicas is chosen to be 0.4 ps. In Fig. 1(b), the blue line is /D(t)/, while the black line is /D(t) − D′(t)/ according to equations (1, 2, 3). The dotted frame illustrates for the filter window needed in traditional SPIDER. We can see the ac components of the black and blue lines are well coincided. However, compared with the blue line, the black line keeps the values very close to zero in the region from −0.32 to 0.32 ps, that is to say, the dc component in blue line is well removed experimentally. This phenomenon, in turn, is a good evidence of the π phase-difference between the two interferograms in Fig. 1(a). Figure 1(c) presents some results of the electric-field reconstruction by traditional SPIDER with different temporal widths of the filter windows (τw = 0.2, 0.3 and 0.4 ps) and our TSPS-SPIDER (black line). The measured pulse duration (FWHM) is about 42 fs. The inconsistencies are observable among the measured temporal phases (green, blue and red dashed lines) with different values of τw by traditional SPIDER method. Comparatively speaking, the difference is more obvious between the three dashed lines (the green, blue and red lines) and the black dashed line. However, if τ increases to 0.5 ps, as shown in Fig. 1(d), the temporal phase lines are well coincided in the temporal region from −0.15 to 0.15 ps for the different filter windows by traditional SPIDER method, and all of them go very closely to that by our TSPS-SPIDER. On these grounds, the inconsistencies among the green, blue and red dashed lines in Fig. 1(c) implies that different width of filter window may introduce different phase errors because the picked ac component isn’t entire and clear enough17, whereas the difference of the phases by the traditional SPIDER from by the TSPS-SPIDER shall be attributed to the removal of the dc. Accordingly, the TSPS-SPIDER can avoid efficiently the effects not only from the filter window width but also from the time delay τ.


Two-step phase-shifting SPIDER
The two measured spectral interferograms I1 (black line) and I2 (red line) with π phase-difference (a); /D(t)/ (blue line) and /D(t) − D′(t)/ (black line) (b); the reconstructed temporal intensity and phase profiles with different filter windows: τw = 0.2, 0.3 and 0.4 ps when τ = 0.4 ps (c); and the reconstructed results under the same conditions of (c) except τ = 0.5 ps (d).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5036035&req=5

f1: The two measured spectral interferograms I1 (black line) and I2 (red line) with π phase-difference (a); /D(t)/ (blue line) and /D(t) − D′(t)/ (black line) (b); the reconstructed temporal intensity and phase profiles with different filter windows: τw = 0.2, 0.3 and 0.4 ps when τ = 0.4 ps (c); and the reconstructed results under the same conditions of (c) except τ = 0.5 ps (d).
Mentions: Figure 1(a) shows two recorded spectral interferograms (I1 and I2). During recording I1 and I2, the only difference is the test sub-pulse reflected from M1 (see Section Method) has π phase-shifting by rotating the QW with 90°. As predicted, Fig. 1(a) reflects clearly the π phase-difference between the two interferograms. Here, the test pulse is an 800 nm femtosecond pulse train with a bandwidth of 26 nm and the delay τ between the pulse replicas is chosen to be 0.4 ps. In Fig. 1(b), the blue line is /D(t)/, while the black line is /D(t) − D′(t)/ according to equations (1, 2, 3). The dotted frame illustrates for the filter window needed in traditional SPIDER. We can see the ac components of the black and blue lines are well coincided. However, compared with the blue line, the black line keeps the values very close to zero in the region from −0.32 to 0.32 ps, that is to say, the dc component in blue line is well removed experimentally. This phenomenon, in turn, is a good evidence of the π phase-difference between the two interferograms in Fig. 1(a). Figure 1(c) presents some results of the electric-field reconstruction by traditional SPIDER with different temporal widths of the filter windows (τw = 0.2, 0.3 and 0.4 ps) and our TSPS-SPIDER (black line). The measured pulse duration (FWHM) is about 42 fs. The inconsistencies are observable among the measured temporal phases (green, blue and red dashed lines) with different values of τw by traditional SPIDER method. Comparatively speaking, the difference is more obvious between the three dashed lines (the green, blue and red lines) and the black dashed line. However, if τ increases to 0.5 ps, as shown in Fig. 1(d), the temporal phase lines are well coincided in the temporal region from −0.15 to 0.15 ps for the different filter windows by traditional SPIDER method, and all of them go very closely to that by our TSPS-SPIDER. On these grounds, the inconsistencies among the green, blue and red dashed lines in Fig. 1(c) implies that different width of filter window may introduce different phase errors because the picked ac component isn’t entire and clear enough17, whereas the difference of the phases by the traditional SPIDER from by the TSPS-SPIDER shall be attributed to the removal of the dc. Accordingly, the TSPS-SPIDER can avoid efficiently the effects not only from the filter window width but also from the time delay τ.

View Article: PubMed Central - PubMed

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.

No MeSH data available.


Related in: MedlinePlus