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High-Acquisition-Rate Single-Shot Pump-Probe Measurements Using Time-Stretching Method

View Article: PubMed Central - PubMed

ABSTRACT

Recent advances of ultrafast spectroscopy allow the capture of an entire ultrafast signal waveform in a single probe shot, which greatly reduces the measurement time and opens the door for the spectroscopy of unrepeatable phenomena. However, most single-shot detection schemes rely on two-dimensional detectors, which limit the repetition rate of the measurement and can hinder real-time visualization and manipulation of signal waveforms. Here, we demonstrate a new method to circumvent these difficulties and to greatly simplify the detection setup by using a long, single-mode optical fiber and a fast photodiode. Initially, a probe pulse is linearly chirped (the optical frequency varies linearly across the pulse in time), and the temporal profile of an ultrafast signal is then encoded in the probe spectrum. The probe pulse and encoded temporal dynamics are further chirped to nanosecond time scales using the dispersion in the optical fiber, thus, slowing down the ultrafast signal to time scales easily recorded with fast detectors and high-bandwidth electronics. We apply this method to three distinct ultrafast experiments: investigating the power dependence of the Kerr signal in LiNbO3, observing an irreversible transmission change of a phase change material, and capturing terahertz waveforms.

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The results of the single-shot terahertz measurements.(a) The probe profiles with and without the terahertz waves as the relative delay between THz and probe pulses was changed. (b) THz time traces compared to the step scan method. The black line indicates the time traces captured using the traditional step-scan method. The data with five different relative delay times are shown to demonstrate the precise measurement of the terahertz waveforms.
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f4: The results of the single-shot terahertz measurements.(a) The probe profiles with and without the terahertz waves as the relative delay between THz and probe pulses was changed. (b) THz time traces compared to the step scan method. The black line indicates the time traces captured using the traditional step-scan method. The data with five different relative delay times are shown to demonstrate the precise measurement of the terahertz waveforms.

Mentions: Finally, we apply this technique to the terahertz spectroscopy and examine the reliability of measurements of more complicated waveforms. Broadband THz radiation is generated via optical rectification of 1200 nm light in the organic THz generation crystal OH131, in which the water vapor absorption and the OH1 phonons imprint modulations in the generated terahertz waveforms. The generated THz radiation is detected using an electro-optic sampling method as shown in Fig. 1. Figure 4a illustrates the observed output pulse-profiles from the photodiode with and without terahertz pulses, for different relative delay times between the terahertz pulse and probe pulse. We clearly see the difference of the waveforms induced by the terahertz pulses. By normalizing the terahertz signal by a reference probe pulse (grey lines in Fig. 4a), ΔI(t)/I(t), the THz waveform can readily be compared to that recorded with a conventional stage scan method (the dark line in Fig. 4b, recorded by stepping a delay stage to change the relative delay between THz and a ~100 fs 800 nm probe pulse).


High-Acquisition-Rate Single-Shot Pump-Probe Measurements Using Time-Stretching Method
The results of the single-shot terahertz measurements.(a) The probe profiles with and without the terahertz waves as the relative delay between THz and probe pulses was changed. (b) THz time traces compared to the step scan method. The black line indicates the time traces captured using the traditional step-scan method. The data with five different relative delay times are shown to demonstrate the precise measurement of the terahertz waveforms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120281&req=5

f4: The results of the single-shot terahertz measurements.(a) The probe profiles with and without the terahertz waves as the relative delay between THz and probe pulses was changed. (b) THz time traces compared to the step scan method. The black line indicates the time traces captured using the traditional step-scan method. The data with five different relative delay times are shown to demonstrate the precise measurement of the terahertz waveforms.
Mentions: Finally, we apply this technique to the terahertz spectroscopy and examine the reliability of measurements of more complicated waveforms. Broadband THz radiation is generated via optical rectification of 1200 nm light in the organic THz generation crystal OH131, in which the water vapor absorption and the OH1 phonons imprint modulations in the generated terahertz waveforms. The generated THz radiation is detected using an electro-optic sampling method as shown in Fig. 1. Figure 4a illustrates the observed output pulse-profiles from the photodiode with and without terahertz pulses, for different relative delay times between the terahertz pulse and probe pulse. We clearly see the difference of the waveforms induced by the terahertz pulses. By normalizing the terahertz signal by a reference probe pulse (grey lines in Fig. 4a), ΔI(t)/I(t), the THz waveform can readily be compared to that recorded with a conventional stage scan method (the dark line in Fig. 4b, recorded by stepping a delay stage to change the relative delay between THz and a ~100 fs 800 nm probe pulse).

View Article: PubMed Central - PubMed

ABSTRACT

Recent advances of ultrafast spectroscopy allow the capture of an entire ultrafast signal waveform in a single probe shot, which greatly reduces the measurement time and opens the door for the spectroscopy of unrepeatable phenomena. However, most single-shot detection schemes rely on two-dimensional detectors, which limit the repetition rate of the measurement and can hinder real-time visualization and manipulation of signal waveforms. Here, we demonstrate a new method to circumvent these difficulties and to greatly simplify the detection setup by using a long, single-mode optical fiber and a fast photodiode. Initially, a probe pulse is linearly chirped (the optical frequency varies linearly across the pulse in time), and the temporal profile of an ultrafast signal is then encoded in the probe spectrum. The probe pulse and encoded temporal dynamics are further chirped to nanosecond time scales using the dispersion in the optical fiber, thus, slowing down the ultrafast signal to time scales easily recorded with fast detectors and high-bandwidth electronics. We apply this method to three distinct ultrafast experiments: investigating the power dependence of the Kerr signal in LiNbO3, observing an irreversible transmission change of a phase change material, and capturing terahertz waveforms.

No MeSH data available.