Search

A low-loss broadband power splitter based on X-cut lithium niobate is proposed by utilizing the multimode interference coupler with a shallow-etched slot, wedge-shaped structure and SiO2 cladding. The multimode waveguide with a shallow-etch slot could reduce the sensitivity of multi-mode region on the wavelength and reach to high-quality imaging requirements. Results show that there is an excess loss around 0.01 dB at the operation wavelength of 1550 nm, a broad operation bandwidth of ∼ 1314 nm and large tolerance in the shallow-etching. Additionally, our proposed device has been compared with the published and conventional multimode interference coupler for presenting good low-loss and broad bandwidth.

Graphene, as two-dimensional material with many properties of the gate-voltage tunable Fermi-level and zero band gap, can be utilized for optical modulators by the integration with other material. In this work, an electro-optic modulator based on the fiber-surface waveguide and graphene capacitance has been proposed with the device length of 50 μm, featuring excellent controllable polarization modulation (polarization extinction ratio over 0.12 dB/μm), large modulation bandwidth of ∼40 GHz @ hBN and ∼25 GHz @ Al2O3, and energy consumption low to 11.5 pJ/bit for hBN and 4 pJ/bit for Al2O3. The polarization can be controlled by tuning the core radius from 130 nm for the TE polarized modulation with modulation efficiency over ∼2.56 dB V−1 (Al2O3) and ∼1.15 dB V−1 (hBN) to 170 nm for the TM polarized modulation efficiency up to ∼3.03 dB V−1 (Al2O3) and ∼1.3 dB/V (hBN). This work not only promotes the development of future polarization modulation technology, but also paves the way toward multifunctional fiber devices and systems.

Efficient Cherenkov radiation (CR) is experimentally generated by a soliton self-frequency shift (SSFS) in a knot of hollow-core photonic crystal fiber (HC-PCF). When the angle of the half-wave plate is rotated from 0° to 45°, the Raman soliton shifts from 2227 to 2300 nm, the output power of the CR increases 8.15 times, and the maximum output power ratio of the CR at 556 nm to the residual pump is estimated to be 20:1. The width of the output optical spectrum at visible wavelengths broadens from 25 to 45 nm, and the conversion efficiency of the CR can be above 28%. Moreover, the influences of the pump polarization and wavelength on the CR are studied, and the corresponding nonlinear processes are discussed.

Highly efficient Cherenkov radiation (CR) is generated by the soliton self-frequency shift (SSFS) in the irregular point of a hollow-core photonic crystal fiber (HC-PCF) in our laboratory. The impacts of pump power and wavelength on the CR are investigated, and the corresponding nonlinear processes are discussed. When the average power of the 120 fs pump pulse increases from 500 mW to 700 mW, the Raman soliton shifts from 2210 nm to 2360 nm, the output power of the CR increases by 2.3 times, the maximum output power ratio of the CR at 539 nm to that of the residual pump is calculated to be 24.32:1, the width of the output optical spectrum at the visible wavelength broadens from 35 nm to 62 nm, and the conversion efficiency η of the CR in the experiment can be above 32%.

Using a photonic crystal fiber with a zero dispersion wavelength of the fundamental mode at 780 nm designed and fabricated in our lab, the ultraviolet and mid-infrared continua are generated by cross-phase modulation between red-shift solitons and blue-shift dispersive waves. The dependences of continuum on the pump power and wavelength are investigated. With the pump working at 820 nm, when the pump power increases from 300 to 500 mW, the bandwidths of ultraviolet and mid-infrared continua change from 80 to 140 nm and 100 to 200 nm, respectively. The wavelength of ultraviolet continuum is below 246 nm, and the wavelength of mid-infrared continuum exceeds 2500 nm. Moreover, the influences of pump power on wavelength and conversion efficiency of different parts of continua are also demonstrated.