Data communications have been growing at a speed even faster than Moore's Law, with a 44-fold increase
expected within the next 10 years. Data Transfer on such scale would have to recruit optical
communication technology and inspire new designs of light sources, modulators, and photodetectors. An
ideal optical modulator will require high modulation speed, small device footprint and large operating
bandwidth. Silicon modulators based on free carrier plasma dispersion effect and compound
semiconductors utilizing direct bandgap transition have seen rapid improvement over the past decade. One
of the key limitations for using silicon as modulator material is its weak refractive index change, which
limits the footprint of silicon Mach-Zehnder interferometer modulators to millimeters. Other approaches
such as silicon microring modulators reduce the operation wavelength range to around 100 pm and are
highly sensitive to typical fabrication tolerances and temperature fluctuations. Growing large, high quality
wafers of compound semiconductors, and integrating them on silicon or other substrates is expensive,
which also restricts their commercialization. In this work, we demonstrate that graphene can be used as the
active media for electroabsorption modulators. By tuning the Fermi energy level of the graphene layer, we
induced changes in the absorption coefficient of graphene at communication wavelength and achieve a
modulation depth above 3 dB. This integrated device also has the potential of working at high speed.
The resonance enhanced Goos-Hanchen shifts at attenuated total internal reflection enables the possibility for highly sensitive surface plasmon resonance sensor. The observed giant displacements result from the singular phase retardation at the resonance where the phase is continuous but changes dramatically. The phenomenon is proposed for chemical sensing and the superior sensitivity is demonstrated.
Near-field multiphoton optical lithography is demonstrated by using ~120 fs laser pulses at 790 nm in an apertureless near-field optical microscope, which produce the lithographic features with ~ 70 nm resolution. The technique takes advantage of the field enhancement at the extremity of a metallic probe to induce nanoscale multiphoton absorption and polymerization in a commercial photoresist, SU-8. Even without optimization of the resist or laser pulses, the spatial resolution of this technique is as high as λ/10, nearly a factor of two smaller than the previous multiphoton lithography in the far field.
Conference Committee Involvement (1)
New Concepts in Solar and Thermal Radiation Conversion and Reliability
19 August 2018 | San Diego, California, United States