Precision measurement of the high-frequency signals using generalized lock-in. (a) is the raw signal, (b) is the response of the digital cavity with varying cavity folds, N c to the upshifted signal, and (c) is the comparison of the cavity response with N c = 5 × 107 to the signals acquired at 0.5 s time delay.
Schematic of the setup for recording the noisy data using photo-diode (PD). The laser beam from the He-Ne laser is split into two beams using a beam splitter BS1. The phase of each of the beams is modulated using acousto-optic modulators (AOMs) and combined again using another beam splitter BS2. The intensity of the combined beam is modulated at the difference frequency of the AOMs.
Photo-diode signal for modulated light. (a) shows the signal at 50 KHz, (b) shows the noisy signal at 4 MHz, (c) shows the digital cavity response to the 50 KHz signal, (d) shows the similar response from the 4 MHz signal, (e) shows the photo-diode signal vs. the modulation frequency of the light, and (f) shows the signal to noise ratio for the different modulation frequencies. The maximum of the cavity response as shown in (c) and (d) for the measurements of various signals between 50 KHz and 4 MHz is taken as the intensity in (e).
Signal retrieval at very high frequencies. (a) shows digitized signal, (b) shows the amplitude of the signal around 30 MHz after applying a digital cavity with N c = 2000, and (c) shows the amplitude of the signal around 30 MHz after applying a digital cavity with N c = 500 000.
Cavity response to the pure sine signals generated by the computer around 5 MHz. (a) uses 32 bit floating number system and (b) uses 128 bit number system.
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