Hiroshi Maeda

In a two-dimensional photonic crystal T-shaped waveguide with a passive switching function, the routing characteristics depending on the input light amplitude and the wavelength are numerically demonstrated by using the frequency-dependent finite-difference time domain method. For typical input electric field amplitudes ( E ₀ = 0.1, 0.5, 1.0, and 1.5 [V/m]), the distribution ratio to the outputs is evaluated from the electric field profile. Additionally, the cross-correlation coefficient and normalized power spectra are considered. For the add/drop circuit in wavelength division multiplexing (WDM) optical network, it has been determined that the add/drop signal wavelength can be tuned by engineering the duplexer at the branching point with specific pillar radii.

Developing efficient techniques to realize polarization-independent modulators nowadays is still important for on-chip photonic circuits. Here, we propose and theoretically demonstrate a graphene-based T-slot waveguide modulator, which simultaneously supports the TE and TM polarized modes, offering a greater possibility to achieve the polarization-independent modulation. The modulation performance is comprehensively studied in terms of attenuation loss, insertion loss, modulation depth, normalized mode area, bandwidth and power consumption. Optimizations of key characteristic parameters illustrate that the modulator not only offers a mode confinement beyond the diffraction limit (<; λ ² /12 and <; λ ² /8 for TM and TE modes, respectively), but also exhibits an outstanding performance with a modulation depth (MD) of >0.35 dB/μm, a insertion loss (IL) of <; 0.1 dB/μm and a MD discrepancy of <; 0.012 dB/μm for both polarized modes covering the whole S, C and L bands. Particularly, the modulator possesses a compact footprint of 11.6 μm ² , a 3-dB modulation bandwidth of 50 GHz and a power consumption per bit of 2.07 pJ/bit based on theoretical predictions. The polarization-independent operation is also quite robust against the possible fabrication perturbations. Our work may inspire new potential for developing the integrated modulators and opto-electronic interconnects in the advanced polarization-diversity circuits.