Visual observation of photonic Floquet–Bloch oscillations

Bloch oscillations(BOs),an important transport phenomenon,have been studied extensively in static systems but remain mysterious in Floquet systems.Here,by harnessing notions from photonic analogy,we propose a generalization of the existing BOs in photonic Floquet lattices,namely the“photonic Floquet–Bloch oscillations”,which refer to rescaled photonic Bloch oscillations with a period of extended least common multiple of the modulation period and the Bloch oscillation period.Next,we report the first visual observation of such photonic Floquet–Bloch oscillations(FBOs)by employing waveguide fluorescence microscopy.Most significantly,the FBOs surpass the existing BOs in Floquet systems and exhibit exotic properties on their own,including fractal spectrum and fractional Floquet tunneling.This new transport mechanism offers an intriguing method of wave manipulation that may contribute to rapidly developing fields in photonics,condensed matter physics,and quantum physics.

Silicon-on-insulator-based microwave photonic filter with widely adjustable bandwidth

We demonstrate a silicon-based microwave photonic filter(MPF) with flattop passband and adjustable bandwidth. The proposed MPF is realized by using a 10 th-order microring resonator(MRR) and a photodetector,both of which are integrated on a photonic chip. The full width at half-maximum(FWHM) bandwidth of the optical filter achieved at the drop port of the 10 th-order MRR is 21.6 GHz. The ripple of the passband is less than 0.3 dB, while the rejection ratio is 32 dB. By adjusting the deviation of the optical carrier wavelength from the center wavelength of the optical bandpass filter, the bandwidth of the MPF can be greatly changed. In the experiment, the FWHM bandwidth of the proposed MPF is tuned from 5.3 to 19.5 GHz, and the rejection ratio is higher than 30 dB.

Compact vector twist sensor using a small period long period fiber grating inscribed with femtosecond laser

We propose and demonstrate a sensitive vector twist sensor based on a small period long period fiber grating(SP-LPFG)fabricated with a femtosecond(fs)laser.The fabricated SP-LPFG is compact in size(2.8 mm)and shows strong polarization dependent peaks in its transmission spectrum due to the vectorial behavior of high-order cladding modes.Twist sensing is realized by monitoring the polarization dependent peaks,since the polarization of input light changes with fiber twist.The proposed sensor can be interrogated by the peak intensity and wavelength,with high twist sensitivity that reaches 0.257 dB/deg and 0.115 nm/deg,respectively.