Coherent satellites in multispectral regenerative frequency microcombs

Abstract

Multi-spectral frequency combs provide frontier architectures for laser standoff spectroscopy, optical clockwork, and high-capacity optical communications. Frequency microcombs, aided by their high-quality resonances and inherent third-order nonlinear susceptibility, have demonstrated remarkable impact in frequency metrology and synthesis. However, microcombs are often with limited spectral bandwidth bounded by the intrinsic second-order chromatic dispersion and the consequently low intensities at the spectral edges. To enhance the applications of frequency combs, a spectrally-broad comb generation scheme is often desired. Here we report coherent satellite clusters in multi-spectral regenerative frequency microcombs with enhanced intensities at the octave points and engineered frequency span. Beyond the conventional bandwidth of parametric oscillation, the regenerative satellites are facilitated by higher-order dispersion control allowing for multiphase-matching in the microcavities. The frequency span of the multi-spectral regenerative satellites is deterministically controlled from 57 THz to 126 THz by pumping at C-and Lbands. We demonstrate that the regenerative satellite preserves the coherence with the central comb through the nonlinear parametric process. We further show the mirrored appearance of the satellite transition dynamics including each comb state that are simultaneously observed at the central comb. These multi-spectral regenerative satellites 2 extend the scope of parametric-based frequency combs and provide a unique platform with wide applications.

Stretching the spectra of Kerr frequency combs with self-adaptive boundary silicon waveguides

“…14 and is thus used hereafter as the reference case. The primary comb lines 12,13,15 that are generated in the early stage of the comb generation process provide information that is useful for evaluating the bandwidth of parametric process; [24][25][26] it is also plotted for point 3 at the bottom of Fig. 1(d).…”

“…It is thus very interesting to reduce and engineer the dispersion coefficient D globally while keeping the other parameters fixed (γ, P in , etc.). [22][23][24][25][26] This matter is discussed in the next section of the article.…”

“…Consequently, addressing the problem of the spectral bandwidth of microcombs in silicon waveguides is an important point. Broadband phase-matching was shown based on the optimization of high order dispersion terms, e.g., by relying on fourth-order dispersive waveguides, [22][23][24][25][26] or by implementing slightly etched rib geometries. 6 Yet, the proposed solutions require complex fabrication processes, with deposition of different materials or a tight control of the rib and slab thicknesses, respectively.…”

Spectral extension and synchronization of microcombs in a single microresonator

“…Broadband optical frequency combs are required for precise optical frequency metrology and spectroscopy. Soliton microcombs have been demonstrated with spectral bandwidths reaching more than one octave [14][15][16][17][18][19] , and octave-spanning soliton microcombs with THz mode spacing directly realized, using Si 3 N 4 resonators by carefully engineering their dispersion properties 14,15 . Spectra of soliton microcombs with GHz mode spacing can be externally broadened to cover an octave, using highly nonlinear fibers 16 or nonlinear waveguides 18 .…”

Gain-assisted chiral soliton microcombs

“…So far, frequency microcombs have been applied widely in laser-based light detection and ranging (LiDAR) [20][21][22] , high-speed optical communication networks 8,9,23 , on-chip spectroscopy 24,25 , and quantum sources [26][27][28] . To push the practicality of these applications, considerable effort has been made recently, such as turnkey soliton generation 29 , broadband spectral coverage [30][31][32] , high efficiency energy conversion [33][34][35] . Beyond the significant progresses in soliton generation, the ability to dynamically observe and control the soliton properties 36 also lies at the heart of various highperformance applications.…”