Spatial Heterodyne

et al. 2020

Opt. Eng.

Self Cite

To simulate the effects of multiple-longitudinal modes and rapid fluctuations in center frequency, we use sinusoidal phase modulation and linewidth broadening, respectively. These effects allow us to degrade the temporal coherence of our master-oscillator laser, which we then use to conduct digital holography experiments. In turn, our results show that the coherence efficiency decreases quadratically with fringe visibility and that our measurements agree with our models to within 1.8% for sinusoidal phase modulation and 6.9% for linewidth broadening.

Section: Introductionmentioning

confidence: 93%

Digital holography experiments with degraded temporal coherence

Thornton¹,

Mao²,

et al. 2020

Opt. Eng.

Self Cite

“…where here, • is the spatial average over all pixels and q I is the image plane sampling quotient, which we measured to be 2.7 [26]. The π/4 q 2 I term in Eq.…”

Section: B Data Processingmentioning

confidence: 96%

Impacts of Laboratory Vibrations and Laser Flicker Noise on Digital Holography

Thornton

IEEE J. Quantum Electron.

Rice

et al. 2020

Self Cite

In this paper, we experimentally demonstrate the impacts of laboratory vibrations and laser flicker noise on digital holography (DH). Specifically, we measure both the vibration efficiency and the coherence efficiency of our DH system at various focal-plane array integration times and path-length differences between the signal and reference. These efficiencies, in practice, contribute to the overall mixing efficiency, which is a measure for how well the detected signal and reference interfere. The results show that when the integration time is ≤1 ms, the laboratory vibrations are negligible with a vibration efficiency of 100%; however, when the integration time equals 100 ms, the laboratory vibrations lead to a 94% vibration efficiency. In addition, the results show that the effective coherence length of the master-oscillator (MO) laser increases by 280% when the integration time decreases from 100 ms to 100 µs. To account for this outcome, we present a model of the coherence efficiency based on the frequency noise of the MO laser. The model fit to the DH data then shows that the frequency of the MO laser is flicker-noise dominated. As a result, decreasing the integration time improves the overall mixing efficiency because of highpass filtering in both the vibration efficiency and the coherence efficiency. Based on previous published efforts, these results have direct ties to the achievable signal-to-noise ratio of a DH system.

“…pulse with a scattered, on-axis, converging signal pulse [2], [11]. The power definition of the SNR for this recording geometry is given by…”

Section: Jqe-136108-2022mentioning

confidence: 99%

“…These scenarios lead to limitations in the utility of digital-holographic systems, especially when the temporal coherence of the MO laser is degraded. To quantify these limitations, the signal-to-noise ratio (SNR) can be used to characterize system performance [11], [12]. In practice, there are several phenomena that lead to SNR loss, which are accounted for using component efficiencies that make up the total-system efficiency.…”

Section: Introductionmentioning

confidence: 99%

Spectral Broadening Effects on Pulsed-Source Digital Holography

Owens

IEEE J. Quantum Electron.

Perram

2023

Using a pulsed configuration, a digital-holographic system is setup in the off-axis image plane recording geometry, and spectral broadening via pseudo-random bit sequence is used to degrade the temporal coherence of the master-oscillator laser. The associated effects on the signal-to-noise ratio are then measured in terms of the ambiguity and coherence efficiencies. It is found that the ambiguity efficiency, which is a function of signal-reference pulse overlap, is not affected by the effects of spectral broadening. The coherence efficiency, on the other hand, is affected. As a result, the coherence efficiency, which is a function of effective fringe visibility, is shown to be a valid performance metric for pulsed-source digital holography.