Photonic Flywheel in a Monolithic Fiber Resonator

We demonstrate the first compact photonic flywheel with sub-fs time jitter (averaging times up to $10\mu \mathrm{s}$) at the quantum-noise limit of a monolithic fiber resonator. Such quantum-limited performance is accessed through novel two-step pumping scheme for dissipative Kerr soliton generation. Controllable interaction between stimulated Brillouin lasing and Kerr nonlinearity enhances the DKS coherence and mitigates the thermal instability challenge, achieving a remarkable 22-Hz intrinsic comb linewidth and an unprecedented phase noise of $-180\mathrm{dBc}/\mathrm{Hz}$ at 945-MHz carrier at free running. The scheme can be generalized to various device platforms for field-deployable precision metrology.

Figure 1

(a) Experimental setup for self-stabilized DKS generation. $L1$ and $L2$: aspheric lens. Inset: picture of the FFP resonator. (b) Cold-cavity transmission spectrum around 1557 nm. Inset: Enlarged view of the transmission and reflection signals across the $P1$ resonance. (c) When the primary laser is polarized along $P1$, efficient SBL generation (inset) followed by DKS frequency comb generation, both polarized along $P2$, is observed and measured.

Figure 2

(a) Schematic of the self-stabilized DKS generation. When the DKS is generated, the $P1$-polarized primary laser remains on the blue-detuned side while the $P2$-polarized SBL secondary pump is pushed to the red-detuned side of the cavity resonances. Such arrangement mitigates the thermal instability and facilitates robust DKS generation. (b) Cavity transmission at both polarizations during the primary laser scan from higher to lower frequencies over a resonance. (c) Principle of the self-stabilized strategy for thermal management and robust DKS generation. Stage I: SBL growth; stage II: DKS generation; stage III: chaotic oscillation; and stage IV: trivial off-resonance state.

Figure 3

(a) rf beat notes of the mixed polarization output (top panel) and the $P2$-polarized DKS frequency comb (bottom panel). (b) Fundamental beat note of the DKS frequency comb on logarithmic scale and linear scale (inset). (c) SDSHI results of the primary laser and the DKS frequency comb, showing a significant linewidth narrowing from 5 kHz to 22 Hz. (d) Top panel: single sideband phase noise of DKS frequency comb scaled at 1-FSR carrier (red solid curve), reaching the quantum-noise limit (blue dashed curve) for offset frequencies above 10 kHz. Bottom panel: sub-optical-cycle integrated timing jitter. (e) Enlarged view of the integrated timing jitter, showing a subfemtosecond jitter for averaging times up to $10\mu \mathrm{s}$.

Figure 4

(a) FROG-retrieved pulse shape and temporal phase. (b) Supercontinuum spanning more than an octave. Inset: spectrum of the amplified single-soliton pulse.