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Abstract Kerr microcombs have drawn substantial interest as mass-manufacturable, compact alternatives to bulk frequency combs. This could enable the deployment of many comb-reliant applications previously confined to laboratories. Particularly enticing is the prospect of microcombs performing optical frequency division in compact optical atomic clocks. Unfortunately, it is difficult to meet the self-referencing requirement of microcombs in these systems owing to the approximately terahertz repetition rates typically required for octave-spanning comb generation. In addition, it is challenging to spectrally engineer a microcomb system to align a comb mode with an atomic clock transition with a sufficient signal-to-noise ratio. Here we adopt a Vernier dual-microcomb scheme for optical frequency division of a stabilized ultranarrow-linewidth continuous-wave laser at 871 nm to an ~235 MHz output frequency. This scheme enables shifting an ultrahigh-frequency (~100 GHz) carrier-envelope offset beat down to frequencies where detection is possible and simultaneously placing a comb line close to the 871 nm laser—tuned so that, if frequency doubled, it would fall close to the clock transition in171Yb+. Our dual-comb system can potentially combine with an integrated ion trap towards future chip-scale optical atomic clocks.
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Fresnel biprism common-path low-coherence digital holography for dynamic light scattering spectroscopy of biological materials
Doppler frequency shifts associated with the motions in cells range from mHz to Hz, requiring ultra-stable interferometry to capture frequency offsets at several parts in 1018. Common-path interferometers minimize the influence of mechanical disturbances when the signal and reference share common optical elements. In this paper, multi-mode speckle self-referencing via a Fresnel biprism demonstrates frequency stability down to 1 mHz. A low-coherence NIR source creates an OCT-like pseudo-coherence-gate in Fourier-domain holography without phase stepping, and the Fourier reconstruction of the self-referencing speckle fields produces an image-domain autocorrelation of the target. Fluctuation spectroscopy of dynamic speckle is performed on a semi-solid lipid emulsion that captures Brownian thermal signatures and on feline tissue culture that measures active intracellular transport. The extension of biodynamic imaging to lower frequencies opens the opportunity for studies of cell crawling in macroscopic living tissues.
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- Award ID(s):
- 2200186
- PAR ID:
- 10569083
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Biomedical Optics Express
- Volume:
- 16
- Issue:
- 2
- ISSN:
- 2156-7085
- Format(s):
- Medium: X Size: Article No. 806
- Size(s):
- Article No. 806
- Sponsoring Org:
- National Science Foundation
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