Fig. 3
From: Large-area photonic circuits for terahertz detection and beam profiling
Large area TFLN circuits for waveform detection and beam profiling in the focal plane. a Experimental configuration for measuring the impulse response of the TFLN chip to a broadband THz pulse test, at different positions of the THz spot along the antenna array (y-axis). b Terahertz waveforms recorded for various values of vertical shifts (solid lines) and fitted envelopes (dashed lines). The waveforms share similar peak-to-peak values as well as dynamic ranges (DR) of about 600 at 300 ms integration time per point, calculated as the ratio between the waveform peak and the corresponding noise floor (recorded at time instants preceding the THz signal and magnified by 400 times in the inset). The position of the peak of the envelope coincides with the pair of antennas that are spatially aligned with the THz beam. The maximum THz modulation remains relatively constant across all measurements. All curves are vertically separated for clarity. c Calculated power spectra of the waveforms in (b), showing larger spectral amplitudes at fPM for the case where the THz spot is aligned with the center of the antenna array. d Terahertz modulation peak (stars) and peak frequency (open circle) show little dependence on any specific antenna pairs under illumination. A zoom-in of peak frequency behavior upon horizontal shifts is given in the inset in (d), showing that the operating frequency only varies by a few percent of the average value. e Experimental configuration for measuring the TFLN chip impulse response to a broadband THz pulse test, as a function of the horizontal shift (z-axis) and to reconstruct the beam profile at the chip. f Terahertz waveforms recorded for various values of horizontal shifts (solid lines) and fitted envelopes (dashed lines). The position of the peak of the envelope and the maximum THz modulation remains relatively constant similar to (b). Curves are vertically separated for clarity. g Calculated power spectra of the waveforms in (f). h Two-dimensional image (z-y plane) of the focused terahertz spot reconstructed combining the waveforms shown in (f). Cut-lines at z = 0 (red circles) and y = 0 (blue diamonds) overlaid with curves profiles (black dotted/dashed line) retrieved via knife-edge measurements
