Ultra-Broadband Second-Harmonic Generation in ZnO Nano-Tetrapod With Over-One-Octave Bandwidth

Broadband nonlinear optical frequency conversion has attracted considerable interest in many applications, such as optical communication, frequency comb generation, and so on. In this letter, we report on the ultra-broadband second-harmonic generation (SHG) from the zinc oxide nano-tetrapod with less stringent phase-matching requirement. Using a super-continuum source together with an optical parametric oscillator as the excitation light, a broadband SHG with over-one-octave bandwidth spanning from the ultraviolet to near-infrared (375-1100 nm) is readily obtained. The SHG dependence of pump polarization and pump power is also characterized systematically. This nanoscale ultra-broadband optical converter may open a new way for various applications ranging from imaging to on-chip all-optical signal processing operations.