High spectro-temporal compression on a nonlinear CMOS-chip

Choi, Ju Won; Şahin, E.; Sohn, Byoung-Uk; Chen, George F. R.; Ng, Doris K. T.; Agarwal, Anuradha M.; Kimerling, Lionel C.; Tan, Dawn T. H.

doi:10.1038/s41377-021-00572-z

Cited by 25 publications

(9 citation statements)

References 50 publications

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“…Fully integrated on chip solution, that combines time lens with the Bragg grating on the same chip would rely on a beam splitter instead of the circulator (that are still hard to implement on-chip), resulting in an extra 6-dB loss. One approach to mitigate this is to utilize recently demonstrated coupled Bragg grating structure 40 .…”

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confidence: 99%

Integrated femtosecond pulse generator on thin-film lithium niobate

Barton

Cheng

et al. 2022

Nature

126

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Integrated femtosecond pulse and frequency comb sources are critical components for a wide range of applications, including optical atomic clocks 1 , microwave photonics 2 , spectroscopy 3 , optical wave synthesis 4 , frequency conversion 5 , communications 6 , lidar 7 , optical computing 8 , and astronomy 9 . The leading approaches for on-chip pulse generation rely on mode locking inside microresonator with either third-order nonlinearity 10 or with semiconductor gain 11,12 . These approaches, however, are limited in noise performance, wavelength tunability and repetition rates 10,13 . Alternatively, sub-picosecond pulses can be synthesized without modelocking, by modulating a continuous-wave (CW) single-frequency laser using a cascade of electro-optic (EO) modulators 1,[14][15][16][17] . This method is particularly attractive due to its simplicity, robustness, and frequency-agility but has been realized only on a tabletop using multiple discrete EO modulators and requiring optical amplifiers (to overcome large insertion losses), microwave amplifiers, and phase shifters. Here we demonstrate a chip-scale femtosecond pulse source implemented on an integrated lithium niobate (LN) photonic platform 18 , using cascaded low-loss electro-optic amplitude and phase modulators and chirped Bragg grating, forming a time-lens system 19 . The device is driven by a CW distributed feedback (DFB) chip laser and controlled by a single CW microwave source without the need for any stabilization or locking. We measure femtosecond pulse trains (520 fs duration) with a 30-GHz repetition rate, flat-top optical spectra with a 10-dB optical bandwidth of 12.6 nm, individual comb-line powers above 0.1 milliwatt, and pulse energies of 0.54 picojoule. Our results represent a tunable, robust and low-cost integrated pulsed light source with CW-to-pulse conversion efficiencies an order of magnitude higher than achieved with previous integrated sources. Our pulse generator can find applications from ultrafast optical measurement 19,20 to networks of distributed quantum computers 21,22 .The ability to generate ultrashort, broadband and high-peak-power optical pulses on-chip has been a long-sought-after goal. The rapid advancement of low-loss nanophotonic waveguides has reduced the pulse energy for achieving nonlinear spectral broadening across octaves of bandwidth to sub-picojoules via supercontinuum generation 23 . However, all demonstrations to date rely on a table-top pulse laser source which increases the system complexity, size, and cost, and thus hinders practical applications. In addition, optical pulses can be generated via microresonator frequency comb sources (for short, microcombs) through coupling a continuous-wave laser into a highquality-factor microresonator 10 . However, microcombs are limited by their low efficiencies (ususally < 2%), comb-line power and high repetition rates, resulting in only tens of femtojoule pulse energies 10,24,25 . An alternative approach, based on compact and electrically pumped on-chip semiconductor mode...

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confidence: 99%

Integrated femtosecond pulse generator on thin-film lithium niobate

Barton

Cheng

et al. 2022

Nature

126

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“…In previous work, ultra-silicon-rich-nitride films demonstrated a nonlinear refractive index 100 times greater than stoichiometric silicon nitride [8,[37][38][39][40]. Prevailing characterization of silicon-nitride thin films fabricated with different ratios of precursor gases suggests that the linear and nonlinear refractive indices of the SRN:D films increase correspondingly with silicon content [38,[41][42][43][44].…”

Section: Discussionmentioning

confidence: 93%

Nonlinear optical characterization of deuterated silicon-rich nitride waveguides

Chia

Chen

Cao

et al. 2021

OSA Nonlinear Optics 2021

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Chemical vapor deposition-based growth techniques allow flexible design of CMOS-compatible materials. Here, we report the deuterated silicon-rich nitride films grown using plasma-enhanced chemical vapor deposition. The linear and nonlinear properties of the films are characterized. We compare the absorption at 1550nm wavelength region for films grown with SiH4 and SiD4, and experimentally confirm that the silicon-rich nitride films grown with SiD4 eliminates Si-H related absorption. Waveguides fabricated on the films are further shown to possess a linear and nonlinear refractive index of 2.46 and 9.8×10 -18 m 2 W -1 respectively.

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“…We designed the topological photonic waveguide using ultra-silicon-rich nitride (USRN), which possesses a high nonlinear figure of merit and negligible nonlinear losses at 1550 nm 44 – 46 . USRN is therefore a prime platform on which to observe Kerr effects occurring in the topological mode.…”

Section: Resultsmentioning

confidence: 99%

A topological nonlinear parametric amplifier

et al. 2022

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Topological boundary states are well localized eigenstates at the boundary between two different bulk topologies. As long as bulk topology is preserved, the topological boundary mode will endure. Here, we report topological nonlinear parametric amplification of light in a dimerized coupled waveguide system based on the Su-Schrieffer-Heeger model with a domain wall. The good linear transmission properties of the topological waveguide arising from the strong localization of light to the topological boundary is demonstrated through successful high-speed transmission of 30 Gb/s non-return-to-zero and 56 Gb/s pulse amplitude 4-level data. The strong localization of a co-propagating pump and probe to the boundary waveguide is harnessed for efficient, low power optical parametric amplification and wavelength conversion. A nonlinear tuning mechanism is shown to induce chiral symmetry breaking in the topological waveguide, demonstrating a pathway in which Kerr nonlinearities may be applied to tune the topological boundary mode and control the transition to bulk states.

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High spectro-temporal compression on a nonlinear CMOS-chip

Cited by 25 publications

References 50 publications

Integrated femtosecond pulse generator on thin-film lithium niobate

Integrated femtosecond pulse generator on thin-film lithium niobate

Nonlinear optical characterization of deuterated silicon-rich nitride waveguides

A topological nonlinear parametric amplifier

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