Abstract
Broadband on-chip optical frequency combs (OFCs) are important for expanding the functionality of photonic integrated circuits. Here, we demonstrate a huge local optical nonlinearity enhancement using graphene. A waveguide is decorated with graphene by precisely manipulating graphene’s area and position. Our approach simultaneously achieves both an extremely efficient supercontinuum and ultra-short pulse generation. With our graphene-decorated silicon waveguide (G-SWG), we have achieved enhanced spectral broadening of femtosecond pump pulses, along with an eightfold increase in the output optical intensity at a wavelength approximately 200 nm shorter than that of the pump pulses. We also found that this huge nonlinearity works as a compressor that effectively compresses pulse width from 80 to 15.7 fs. Our results clearly show the potential for our G-SWG to greatly boost the speed and capacity of future communications with lower power consumption, and our method will further decrease the required pump laser power because it can be applied to decorate various kinds of waveguides with various two-dimensional materials.
Highlights
On-chip coherent ultra-broadband light sources, known as broadband on-chip optical frequency combs (OFCs), are recognized as indispensable tools in the application fields of chemical-biological spectroscopy[1,2], broadband molecular sensing[3], waveform generation[4], and high-capacity optical communications[5,6]
Once the ultra-short pulse reaches the graphene-decorated silicon waveguide (G-SWG) in the center of the device, a gigantic nonlinear effect is induced on the SWG, which can be observed as spectrum broadening in the frequency domain through the output side the Parameter name SWG length Graphene length Linear loss of G-SWG Effective nonlinear refractive index of G-SWG Effective mode area two-photon absorption (TPA) coefficient of G-SWG
It was clearly shown that the most suitable graphene length LGr is 200 μm. When it is more than 200 μm, the on-chip OFC bandwidth becomes smaller by TPA
Summary
On-chip coherent ultra-broadband light sources, known as broadband on-chip OFCs, are recognized as indispensable tools in the application fields of chemical-biological spectroscopy[1,2], broadband molecular sensing[3], waveform generation[4], and high-capacity optical communications[5,6]. We found that with current experimental setup, the widest on-chip OFC spectrum (1050–1700 nm) at −60 dB level is generated when the graphene length LGr is 200 μm and graphene position P is 300 μm from the SWG incident side.
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