Interleaved difference-frequency-generation for mid-infrared microcomb spectral densification

Bao, Chengying; Yuan, Zhiquan; Wang, Heming; Wu, Lue; Sung, Keeyoon; Leifer, Stephanie; Lin, Qiang; Vahala, Kerry J.

doi:10.1364/cleo_si.2020.sw3j.1

“…Each EO-comb drive frequency is derived from a corresponding photo-detected soliton repetition frequency and set to be ( N is an integer). This results in interleaving of the near-IR combs and densifies the mid-IR comb line spacing to 22 GHz/ N as described elsewhere 33 . 2.8 and 1.4 GHz mid-IR line spacings are demonstrated, corresponding to N = 8 or 16.…”

Section: Resultsmentioning

confidence: 92%

“…A feature of iDFG DCS is that the spectral resolution can be adjusted by changing the division ratio N 33 . For instance, the full-width at half-maximum (FWHM) of methane P (3) to P (7) transition groups in the ν 3 band are within 10−26 GHz, while the FWHM of ethane P Q 1 to P Q 4 transitions in the ν 7 band are within 4.2−6.9 GHz according to the HITRAN database.…”

Section: Resultsmentioning

confidence: 99%

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Architecture for microcomb-based GHz-mid-infrared dual-comb spectroscopy

Bao

¹

,

Yuan

²

,

Wu

³

et al. 2021

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Dual-comb spectroscopy (DCS) offers high sensitivity and wide spectral coverage without the need for bulky spectrometers or mechanical moving parts. And DCS in the mid-infrared (mid-IR) is of keen interest because of inherently strong molecular spectroscopic signatures in these bands. We report GHz-resolution mid-IR DCS of methane and ethane that is derived from counter-propagating (CP) soliton microcombs in combination with interleaved difference frequency generation. Because all four combs required to generate the two mid-IR combs rely upon stability derived from a single high-Q microcavity, the system architecture is both simplified and does not require external frequency locking. Methane and ethane spectra are measured over intervals as short as 0.5 ms, a time scale that can be further reduced using a different CP soliton arrangement. Also, tuning of spectral resolution on demand is demonstrated. Although at an early phase of development, the results are a step towards mid-IR gas sensors with chip-based architectures for chemical threat detection, breath analysis, combustion studies, and outdoor observation of trace gases.

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“…In microresonators, such Kerr solitons (KSs) have been realized in a wide range of geometries and material systems [7][8][9][10][11][12][13][14] . Soliton microcomb devices have been tested in diverse system demonstrations, including spectroscopy [15][16][17] , coherent communications 18 , range detection [19][20][21] , optical frequency synthesis 22 , exoplanet studies 23,24 , and optical clocks 25 . Progress towards integration of the microcomb with pump and other control functions is also being made [26][27][28] .…”

Section: Introductionmentioning

confidence: 99%

Dirac Solitons in Optical Microresonators

Wang

¹

,

Lu

²

,

Wu

³

et al. 2021

Conference on Lasers and Electro-Optics

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Mode-coupling-induced dispersion has been used to engineer microresonators for soliton generation at the edge of the visible band. Here, we show that the optical soliton formed in this way is analogous to optical Bragg solitons and, more generally, to the Dirac soliton in quantum field theory. This optical Dirac soliton is studied theoretically, and a closed-form solution is derived in the corresponding conservative system. Both analytical and numerical solutions show unusual properties, such as polarization twisting and asymmetrical optical spectra. The closed-form solution is also used to study the repetition rate shift in the soliton. An observation of the asymmetrical spectrum is analysed using theory. The properties of Dirac optical solitons in microresonators are important at a fundamental level and provide a road map for soliton microcomb generation in the visible band.

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“…In microresonators, such Kerr solitons (KSs) have been realized in a wide range of geometries and material systems 7 – 14 . Soliton microcomb devices have been tested in diverse system demonstrations, including spectroscopy 15 – 17 , coherent communications 18 , range detection 19 – 21 , optical frequency synthesis 22 , exoplanet studies 23 , 24 , and optical clocks 25 . Progress towards integration of the microcomb with pump and other control functions is also being made 26 – 28 .…”

Section: Introductionmentioning

confidence: 99%

Dirac solitons in optical microresonators

Wang

¹

,

Lu

²

,

Wu

³

et al. 2020

Self Cite

View full text Add to dashboard Cite

Mode-coupling-induced dispersion has been used to engineer microresonators for soliton generation at the edge of the visible band. Here, we show that the optical soliton formed in this way is analogous to optical Bragg solitons and, more generally, to the Dirac soliton in quantum field theory. This optical Dirac soliton is studied theoretically, and a closed-form solution is derived in the corresponding conservative system. Both analytical and numerical solutions show unusual properties, such as polarization twisting and asymmetrical optical spectra. The closed-form solution is also used to study the repetition rate shift in the soliton. An observation of the asymmetrical spectrum is analysed using theory. The properties of Dirac optical solitons in microresonators are important at a fundamental level and provide a road map for soliton microcomb generation in the visible band.

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Interleaved difference-frequency-generation for mid-infrared microcomb spectral densification

Abstract: Generation of mid-infrared combs (3.3 micron band) with GigaHertz line spacing is demonstrated by interleaved difference-frequency-generation. The method, applied to a 22 GHz repetition-rate microcomb, is useful for spectral densification of sparse microcomb spectra.

Cited by 11 publications

References 6 publications

Architecture for microcomb-based GHz-mid-infrared dual-comb spectroscopy

Architecture for microcomb-based GHz-mid-infrared dual-comb spectroscopy

Dirac Solitons in Optical Microresonators

Dirac solitons in optical microresonators

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