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A scalable and reconfigurable on-chip optical true time delay line consisting of Mach-Zehnder interferometer (MZI) switches and delay waveguides is proposed and demonstrated with the ultra-low-loss silica waveguide platform. The MZI switches provide the reconfiguration of the light traveling paths and hence different delays. Our proposed structure can be easily scaled to an M bit delay line with a slight increase in dimensions. The footprint of our fabricated 1 bit delay line is 33  mm×13  mm (length×width) and can provide a delay of 6.0 ps with an insertion loss of 1.2 dB at the operating wavelength of 1550 nm, while the footprint of the 4 bit delay line is 43  mm×14  mm and can provide a discrete delay tuning from 6.0 to 90.2 ps with a delay deviation lower than 0.2 ps and a tuning response time of 0.84 ms. The insertion losses are lower than ∼2.34  dB, and the extinction ratios are greater than 20.42 dB. The average switching power is ∼132.6  mW. Our proposed optical true time delay lines could find applications for optical beamforming in phased array antennas.

We propose a novel continuously tunable delay line in X-cut lithium niobate thin film driven by graphene electrodes, featuring low power consumption and low half-wave voltagelength product. The use of the graphene electrodes combined with the air slots makes the device quite low power consumption. Our designed device, which has a footprint of 8.9 mm  1.9 mm, is capable of providing a continuously tunable delay range from 0 to 100 ps with minimum 3 dB bandwidth of >20 GHz. By optimizing the width of the waveguide core and the distance between the graphene and the waveguide core, we can obtain the low power consumption and low voltage -length product VπL=1.12 V• cm at 1550 nm when w=2 μm and d=0.3 μm. In addition, the graphene electrode has negligible light absorption with w=2 μm and d=0.3 μm, the switching power is 151 mW without air slots, and the switching power is 95.36 mW with air slots etching depth of 5.3 μm formed on both sides of the waveguides. And further, the air slots formed on both sides and at the bottom of the waveguides make a low switching power of 2.85 mW.

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Since the C2N-h2D crystal was efficiently synthesized, this study aims to investigate bandgap modulation of nanoribbons and nanotubes. Appling Density Functional Theory (DFT), the band-gap modulation of C2N-h2D nanomaterials is researched under elastic strains. The results of the current study indicate that the band gap of C2N-h2D nanoribbons and nanotubes can be tuned along two directions, namely, stretching or compressing nanoribbons and nanotubes when ɛ is changed from -10% to 10% in zigzag and armchair, respectively. This study also finds that the band gap of the C2N-h2D nanoribbons and nanotubes change with increase of widths or the radii of nanotubes. Therefore, the great potential applications of the C2N-h2D nanomaterials have been predicted in strain sensor and optical electronics at nanoscale.