Graphene Controls Laser Frequency Combs

Illustration of a graphene heterogeneous fiber micro resonator. (Source: C. Qin et al., CAS)

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 fiber lasers, generating Kerr solitons in parametric oscillators, or opto-elec­trically modulating lithium niobate micro­resonators with strong second-order non­linearity. For many out-of-lab appli­cations, people desire a compact comb devices with multiple advances, such as all-in-fiber inte­gration, low driven power but high effi­ciency, full stabi­lization, and diverse comb outputs with fast and convenient tuna­bility.

Now, scientists from the Univer­sity of Electronic Science and Technology of China, Nanjing University, Hunan Univer­sity and University of Colorado, Bouder, demons­trated a graphene hetero­geneous fiber micro resonator. Leveraging the electrical tunability of the graphene semi­conductor incorporated in a fiber 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 tunneling 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 %. In conse­quence, mode locked laser frequency combs with unprece­dentedly dynamic tunability are demonstrated, in both funda­mental and harmonic states. Moreover, the graphene inte­grated micro­laser 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.

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

Reference: C. Qin et al.: Electrically controllable laser frequency combs in graphene-fibre microresonators, Light Sci. Appl. 9, 185 (2020); DOI: 10.1038/s41377-020-00419-z

Link: Key Laboratory of Optical Fibre Sensing and Communications, University of Electronic Science and Technology of China, Chengdu, China

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