Journal: Scientific Reports

Article Title: Super-resolved time–frequency measurements of coupled phonon dynamics in a 2D quantum material

doi: 10.1038/s41598-022-22055-w

Figure Lengend Snippet: Comparison of the Short-Time Fourier Transform (STFT), Continuous Wavelet Transform (CWT), and Superlet Transform (SLT) for 0.081 mJ/cm 2 pump fluence ( a – c , respectively) and for 1.278 mJ/cm 2 pump fluence ( d – f , respectively). White lines at 1.6, 1.8, 2, and 2.8 THz are guides to the eye. All transforms use a normalized Log 10 color scaling for ease of comparison. The SLT outperforms the other two techniques in both spectral and temporal resolution.

Article Snippet: We compared two standard transformation methods to the SLT: a Short-Time Fourier Transform (STFT) and a Continuous Wavelet Transform (CWT) using Matlab’s built-in functions (stft() and cwt(), respectively) from the Signal Processing Toolbox and Wavelet Toolbox.

Techniques: Comparison

Journal: Scientific Reports

Article Title: Super-resolved time–frequency measurements of coupled phonon dynamics in a 2D quantum material

doi: 10.1038/s41598-022-22055-w

Figure Lengend Snippet: Demonstration of SLT performance using test pulse series. ( a ) Test pulses with frequency components 2 THz, 1.8 THz, and 1.6 THz, are summed to generate the model signal in panel ( b ). Each pulse is 10 ps in duration and the 1.8 THz component has an additional pulse delayed in time by 0.5 ps from the end of the first pulse. This model signal will let us study the temporal and spectral resolution of the three techniques. The normalized STFT ( c ), CWT ( d ), and SLT ( e ) of the model signal are shown in the bottom panels from left to right. Lineouts ( f ) of each transform taken at 15 ps (denoted by the vertical white lines in the transforms) are shown in the bottom right panel. The additional structure present in the spectral lineout of the SLT demonstrates its improved spectral resolution. Colorbar indicates relative intensity (arb. units).

Article Snippet: We compared two standard transformation methods to the SLT: a Short-Time Fourier Transform (STFT) and a Continuous Wavelet Transform (CWT) using Matlab’s built-in functions (stft() and cwt(), respectively) from the Signal Processing Toolbox and Wavelet Toolbox.

Techniques:

Journal: Scientific Reports

Article Title: Super-resolved time–frequency measurements of coupled phonon dynamics in a 2D quantum material

doi: 10.1038/s41598-022-22055-w

Figure Lengend Snippet: Demonstration of SLT performance using real data taken with 0.081 mJ/cm 2 pump fluence. ( a – c ) STFT, CWT, and SLT spectrograms, respectively. Lineouts were taken at 5 ps ( d ) and 8 ps ( e ) indicated by the vertical white lines in the spectrograms. Horizontal lines at 1.6, 1.8, 2, and 2.8 THz serve as a guide to the eye. The lineouts show that the SLT produces a narrower peak than either alternative, and provide better spectral resolution. The peak at 1.8 THz is not resolved by the CWT or STFT (blue, yellow, respectively), but is clearly present in the SLT lineout (red) at both 5 and 8 ps.

Article Snippet: We compared two standard transformation methods to the SLT: a Short-Time Fourier Transform (STFT) and a Continuous Wavelet Transform (CWT) using Matlab’s built-in functions (stft() and cwt(), respectively) from the Signal Processing Toolbox and Wavelet Toolbox.

Techniques: