Apodization in dual-comb spectroscopy for rapid measurement

Tourigny-Plante, Alex; Guay, Philippe; Genest, Jérôme

doi:10.1364/lacsea.2020.ltu3c.2

Cited by 3 publications

(2 citation statements)

References 8 publications

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“…Fortunately, recent advances in digital phase locking allow one to precisely program real-time apodization by digitally modulating the set points of the phase locks stabilizing the optical frequency comb. 18 Here, we demonstrate real-time apodization with a single free-form dual-comb platform, which allows one to arbitrarily set the pulse time offsets between the combs with high precision. 15,19 While real-time apodization has been used to increase measurement update rates, 8,18 here we use free-form DCS to maintain coherent, attosecond control over the combs during the apodization, and we study the relation between spectral resolution, SNR, covered spectral bandwidth, and update rate.…”

Section: Article Pubsaiporg/aip/appmentioning

confidence: 99%

Broadband dual-comb hyperspectral imaging and adaptable spectroscopy with programmable frequency combs

Giorgetta,

Deschênes,

Lieber

et al. 2024

APL Photonics

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We explore the advantages of a free-form dual-comb spectroscopy (DCS) platform based on time-programmable frequency combs for real-time, penalty-free apodized scanning. In traditional DCS, the fundamental spectral point spacing, which equals the comb repetition rate, can be excessively fine for many applications. While fine point spacing is not itself problematic, it comes with the penalty of excess acquisition time. Post-processing apodization (windowing) can be applied to tailor the resolution to the sample, but only with a deadtime penalty proportional to the degree of apodization. The excess acquisition time remains. With free-form DCS, this deadtime is avoided by programming a real-time apodization pattern that dynamically reverses the pulse periods between the dual frequency combs. In this way, one can tailor the spectrometer’s resolution and update rate to different applications without penalty. We show the operation of a free-form DCS system where the spectral resolution is varied from the intrinsic fine 160 MHz up to 822 GHz by applying tailored real-time apodization. Because there is no deadtime penalty, the spectral signal-to-noise ratio increases linearly with resolution by 5000× over this range, as opposed to the square root increase observed for post-processing apodization in traditional DCS. We explore the flexibility to change resolution and update rate to perform hyperspectral imaging at slow camera frame rates, where the penalty-free apodization allows for optimal use of each frame. We obtain dual-comb hyperspectral movies at a 20 Hz spectrum update rate with broad optical spectral coverage of over 10 THz.

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Section: Article Pubsaiporg/aip/appmentioning

confidence: 99%

Broadband dual-comb hyperspectral imaging and adaptable spectroscopy with programmable frequency combs

Giorgetta,

Deschênes,

Lieber

et al. 2024

APL Photonics

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“…In traditional DCS with lower repetition rate frequency combs, one often samples well beyond this tail, thus acquiring "empty" spectral resolution. Over the years, several methods have sought to circumvent these constraints such as use of high repetition-frequency or mode-interleaved combs [8][9][10][11] , optical sampling by cavity tuning with delay lines [12][13][14] or apodization approaches 1,15,16 , all of which have their own tradeoffs and lack flexibility, for example, to adapt for both high and low spectral resolutions with a single system while optimizing SNR.…”

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confidence: 99%

Free-form dual-comb spectroscopy for compressive sensing and imaging

Giorgetta

Potvin²,

Deschênes³

et al. 2023

Preprint

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Time programmable frequency combs enable new measurement paradigms for dual-comb spectroscopy (DCS) that are free of many of the constraints found in traditional DCS. As opposed to fixing the repetition rate offset between combs, free-form DCS is based on full control of the temporal offset between the dual comb pulse trains, thereby enabling user-selectable sampling patterns that optimize resolution, signal-to-noise ratio, species selectivity or acquisition time. Here we show that free-form DCS enables compressive sensing. We demonstrate compressive sensing at factors up to 155, with a corresponding reduction in acquisition time, while maintaining spectral resolution. We also demonstrate molecular recurrence sampling (which can be thought of as an extreme case of compressive sensing) for detection of a single gas with >15× higher sensitivity than traditional DCS. Finally, free-form DCS can more easily enable spectral imaging since its rf signal is narrow band, in contrast to traditional DCS, and therefore compatible with the finite readout times of focal plane arrays. We demonstrate imaging of methane plumes across a 128×64 pixel focal plane at a 250 Hz rate. In the future, this flexible free-form approach can enable applications ranging from rapid open-path spectroscopy to nonlinear multidimensional comb-based spectroscopy.

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