Frequency-Domain Interferometer for Measurement of the Group- Velocity Walkaway of Ultrashort Pulses in Birefringent Media
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چکیده
A new technique based on frequency-domain interferometry ( F D I ) ' ~ ~ has been used to measure the group-velocity walkaway (GVW) of ultrashort pulses in birefringent media. As the name implies, this technique is based on the spectral interference of two short pulses in the frequency domain and makes use of the intrinsic phase delay between the fast and slow modes of a birefringent medium. Due to the different group delays, two pulses launched along the fast and slow axes will come out of the medium at different times. In the frequency domain, two temporally separated pulses interfere in the same way that two waves with different frequencies do in the time domain. In the frequency-domain interferometer described here, measurement of the modulation period of the interference fringes in the frequency domain gives the GVW directly without the need for further assumptions about the properties of the light source. By analogy with an ordinary interferometer. the two optical axes of the birefringent medium can be regarded as two interfering arms. Apolarizer placed at the output end of the medium combines the two field components to generate interference fringes in the frequency domain. Temporally separated pulses can interfere owing to the linear dispersion of the grating in a Different frequency components propagate along different directions, resulting in a frequency-dependent time delay. Therefore, two temporally separated pulses can physically overlap on the detector surface of the spectrometer. In comparison with other methods, the experimental setup of our interferometer is quite simple, and the alignment is very easy. Of greater significance is the fact that the experimental data is directly related to the GVW and no further curve fitting is needed.
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Frequency-Domain Interferometer for Measurement of the Group-Velocity Walkaway of Ultrashort Pulses in Birefringent Media
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تاریخ انتشار 2008