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The damage behavior of fused silica optics induced by stimulated Brillouin scattering (SBS) was studied theoretically and experimentally based on a coupled-wave theory. The SBS-induced damage mechanism was systematically investigated by analyzing the evolutions of the Stokes-light intensity and induced stress as a function of laser pulse shape, thickness, and surface reflectance of the optics. The results show that the SBS-induced damage often occurs on the front surface of the fused silica optics. The Tophat beam has the most effect on an SBS-induced damage, followed by a focused Gaussian pulse. SBS effect is strongly thickness dependent, which is associated with the gain length. The SBS-induced damage can be efficiently suppressed by decreasing the surface reflection of the optics. Good agreements are obtained between the experimental and theoretical results, which strengthen our understanding of the damage mechanism of fused silica and provide a favorable reference for developing high-power laser systems.

A novel strategy to design a highly birefringent and low loss oligoporous-core THz photonic crystal fiber (PCF) by introducing a single circular air-hole unit into the core area has been revealed. The circular air-hole units can be diversely designed as dual-hole, triple-hole, or other simple anisotropic structures. The characteristics, including birefringence, effective material loss, power fraction, confinement loss, and dispersion, are numerically analyzed in detail based on the full-vector finite element method (FEM). Simulation results show that birefringence up to the order of 3 × 10-2 and low effective material loss down to 20-40% of its bulk material loss could be achieved in a wide frequency range. The newly proposed THz PCF facilitates the fabrication process due to their simple structures with all circular air-holes and may find wide applications in sensing or polarization maintaining transmission systems.

The antireflection (AR) performance and far-field transmittance, depending on the morphology and parameters of subwavelength structures (SWSs), have been investigated by a 3-D finite-difference time-domain (FDTD) method. It is found that far-field transmission characteristics are dominated mainly by period of SWSs. If the period is increased above 220 nm, the far-field transmittance rapidly decreases for a short-wavelength region. An effective and inexpensive method for fabricating disordered SWSs on fused silica has been demonstrated in this paper. An Au nanoscale island mask was formed by lower temperatures thermal dewetted at normal atmosphere. Then, a disordered SWS was fabricated by reactive ion etching (RIE). The average diameter of the Au nanoscale island was easily controlled by the thickness of Au thin films and annealing temperature. The etched depth and shape of fused silica SWSs depend additionally on RIE duration, thus achieving efficient AR characteristics. The measured data and calculated results obtained by the FDTD method exhibit reasonably similar tendencies. The optimized single-side fused silica SWS that is tapered on the tips leads to a significantly high transmissivity value of 96.2%. In addition, it exhibits a broadband AR property at a wavelength range of 400–1100 nm.