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Graphene Controls Laser Frequency Combs in Fibre

Collaborative team of researchers discover a graphene heterogeneous fibre micro resonator that leverages the electrical tunability of the graphene semiconductor.

The development of laser frequency combs has revolutionized optical communication, photonic sensing, precision spectroscopy, and astronomical observation. Stable frequency combs could be achieved via mode locking in rare-earth doped fibre lasers, generating Kerr solitons in parametric oscillators, or opto-electrically modulating lithium niobate micro-resonators with strong second-order nonlinearity. For many out-of-lab applications, people desire a compact comb device with multiple advances, such as all-in-fibre integration, low driven power but high efficiency, full stabilization, and diverse comb outputs with fast and convenient tunability.

In a recently published paper in Light: Science & Applications, scientists from the University of Electronic Science and Technology of China, Nanjing University, Hunan University and University of Colorado, Bouder, demonstrated a graphene heterogeneous fibre micro resonator. Leveraging the electrical tunability of the graphene semiconductor incorporated in a fibre F-P microcavity, they demonstrate dissipative soliton mode-locked laser combs generation, and the capability to control comb dynamics in situ. Taking advantage of the tunnelling diode effect, the researchers realize a remarkable graphene Dirac Fermion tuning from 0 to 0.45 eV. This leads to modulation depth controllable in range of 0.1 to 1.4 percent. In consequence, mode locked laser frequency combs with unprecedentedly dynamic tunability are demonstrated, in both fundamental and harmonic states. Moreover, the graphene integrated micro-laser device provides a powerful way to opto-electrically stabilize the comb lines after 1/2 octave supercontinuum amplification, the phase noise reaches the instrument-limited floor of -130 dBc/Hz at 10 kHz offset, suggesting timing jitter less than 2.5×10-15 seconds per roundtrip.

Such realization of the microcomb’s dynamic control and stabilization, in a graphene heterogeneous fibre microcavity, would provide a new platform at the interface of single atomic layer optoelectronics and ultrafast photonics, lighting versatile applications for arbitrary waveform generation, fibre communication, signal processing, and spectroscopic metrology. [APBN]