We demonstrate the real-time observation of phonon-polariton propagation in ferroelectric LiNbO 3 using a single-shot spectroscopic setup that employs an echelon mirror. The echelon mirror provides a spatially encoded time delay for the probe pulse; therefore, the ultrafast transient behavior of materials can be detected on a single-shot basis. Using optical Kerr gate apparatus, forward and backward propagating E-mode phonon-polaritons were simultaneously induced via an impulsive stimulated Raman scattering process, and subsequently, their dynamics were readily mapped in time-frequency space using heterodyne detection. The two phonon-polaritons appeared on opposite sides of the central probe wavelength and were symmetrically imaged against the ordinary and extraordinary probe lights. By taking into account coupling of the lowest E-mode phonon-polariton to a low-frequency relaxational mode, not only the phonon-polariton dispersion but also the wavevector dependence of the damping rate was unveiled and quantitatively evaluated. V
We demonstrate real-time time-frequency imaging for the autocorrelation traces of ultrashort laser pulses using an echelon mirror fabricated on a Ni block with 500 steps; the echelon mirror is employed to generate spatially encoded time delays for the probe pulses. By using the frequency-resolved optical gating (FROG) technique with the echelon mirror, the time-frequency images of ultrashort laser pulses were successfully mapped in real-time. The chirp characteristics of the laser pulses were also evaluated with the phase-retrieval procedure on a single-shot basis. Our technique provides significant advantages over conventional autocorrelation and FROG techniques, such as single-shot detection of time-frequency images, a small spot size at a nonlinear crystal, chirp-free characteristics of echelon mirrors, and ultrafast measurement capabilities by simply replacing the nonlinear crystal with samples. Hence, we believe that it becomes a powerful spectroscopic tool for monitoring ultrashort laser pulses and for investigating ultrafast dynamics of materials.
We demonstrate single-shot time-frequency imaging spectroscopy with an echelon mirror for measuring ultrashort laser pulses as well as ultrafast responses of materials using the same optical setup. The echelon mirror produces a spatially encoded time delay for the probe pulse whereby both the probe and pump pulses are focused on samples with small spot size. Using the optical Kerr gate apparatus, we successfully mapped the time-frequency images of ultrashort laser pulses and subsequently evaluated the chirp characteristics with the phase-retrieval procedure on a single-shot basis. By simply replacing the Kerr medium with samples, we could also visualize the phonon-polariton oscillations in ferroelectric LiNbO3.
We demonstrate real-time time-frequency imaging for the autocorrelation traces of ultrashort laser pulses using an echelon mirror fabricated on a Ni block with 500 steps; the echelon mirror is employed to generate spatially encoded time delays for the probe pulses. By using the frequency-resolved optical gating (FROG) technique with the echelon mirror, the time-frequency images of ultrashort laser pulses were successfully mapped in real-time. The chirp characteristics of the laser pulses were also evaluated with the phase-retrieval procedure on a single-shot basis. Our technique provides significant advantages over conventional autocorrelation and FROG techniques, such as single-shot detection of time-frequency images, a small spot size at a nonlinear crystal, chirp-free characteristics of echelon mirrors, and ultrafast measurement capabilities by simply replacing the nonlinear crystal with samples. Hence, we believe that it becomes a powerful spectroscopic tool for monitoring ultrashort laser pulses and for investigating ultrafast dynamics of materials.
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