Shande Liu

High-power femtosecond pulse generation in a passively mode-locked Nd:SrLaAlO4 laser

A high optical quality Nd:SrLaAlO4 (Nd:SLA) crystal was grown using the Czochralski method and showed broad fluorescence spectrum with a full width at half maximum value of 34 nm, which is beneficial for generating femtosecond laser pulses. A stable diode-pumped passively mode-locked femtosecond Nd:SLA laser with 458 fs pulse duration was achieved for the first time at a central wavelength of 1077.9 nm. The average output power of the continuous-wave mode-locked laser was 520 mW and the repetition rate was 78.5 MHz.

Femtosecond pulse generation with an a-cut Nd:CaYAlO 4 disordered crystal

We experimentally demonstrated a diode-pumped 587 fs ultrafast laser by using an a-cut Nd:CaYAlO4 crystal. Pumped by an 808 nm fiber-coupled laser diode, a stable continuous-wave mode-locked ultrafast laser was achieved with a semiconductor saturable absorber. The ultrafast pulses had a repetition rate of 75 MHz at the center wavelength of 1080.8 nm. A maximum average output power of the mode-locked laser reached 375 mW delivering a slope efficiency of 9%.

Tunable omnidirectional photonic band gap of one-dimensional photonic crystals containing Dirac semimetals

We have theoretically investigated the tunability of the omnidirectional bandgap (OBG) of a one-dimensional photonic crystal consisting of alternating Dirac semimetals (DSs) and SiO2 dielectrics by adjusting the structural Fermi level. This photonic bandgap (PBG) is strongly dependent on the Fermi level and thickness ratio of the DSs and SiO2 layers. The effects of different parameters such as Fermi level, incident angle, and lattice constant on PBG are analyzed in detail. It is found that the first gap does not change with the change in lattice constant, but it is sensitive to the Fermi level; the width of the omnidirectional PBG increases with the structural Fermi level. The second gap is also sensitive to the Fermi level, the upper and lower frequency limits of this PBG shift to higher frequency, and the width becomes narrower as the Fermi level is increasing, where only one OBG exists in the range of 3.6–4.3 THz for transverse electric polarization. However, as the angle of incidence increases, the ph...

Dynamically tunable broadband linear-to-circular polarization converter based on Dirac semimetals

We propose a dynamically tunable broadband linear-to-circular cross polarization converter based on Dirac semimetals. The proposed converter unit cell consists of a center-cut cross-shaped metallic patterned structure with a sandwiched Dirac semimetal ribbon on a polyimide substrate bottomed with gold. The proposed system converts linear waves to right-hand circular polarized waves in the frequency ranges of 1.5–2.8 THz or to left-hand circular polarized waves in two narrow frequency ranges of 1.20–1.25 and 3.04–3.07 THz. The polarization conversion is dynamically tunable by varying the Fermi energy without re-optimizing the microstructures, which may further tunable polarizers and polarization switchers developments.

Tunable laser operations in a Nd-doped SrLaAlO4 crystal

Tunable laser operations in a disordered crystal, Nd:SrLaAlO4, were experimentally reported. The maximum tuning range of 32 nm from 1063 to 1095 nm was achieved with a birefringent filter (Lyot filter). The maximum output power was 1.66 W at the center wavelength of 1075.5 nm, giving an optical-to-optical efficiency of 30%. The output power over 50% of the tuning range was greater than 0.6 W. The special spectral lines, such as 1073, 1080 and 1083 nm, have a potential application in the field of atom and molecular spectroscopy.