Generation of tunable blue-green light using ZnO periodically poled lithium niobate crystal fiber by self-cascaded second-order nonlinearity

Abstract

Using a novel self-cascaded first-order second-harmonic generation (SHG) and third-order sum-frequency generation (SFG) in a ZnO periodically poled lithium niobate crystal fiber, tunable blue-green light was demonstrated. At a domain pitch of 15.45 μm, the SHG signal and its fundamental signal at 1423.9 nm can satisfy the third-order SFG quasi-phase-matched (QPM) condition. The measured SHG power at 714.2 nm was 12.25 mW under 100 mW input power, and the estimated nonlinear coefficient (d33) achieved was 25.3 pm/V. The self-cascaded SHG+SFG power measured at 477.1 nm was ∼700 μW under 350 mW input power. The maximum internal efficiency of the SHG is 14.84%. The tuning range of the self-cascaded SHG and SFG generated tunable blue-green light was more than 40 nm, from 471.3 to 515 nm. The maximum simulated 3 dB bandwidth achieved using a gradient-period QPM structure is 196 nm, which is from 1476 to 1672 nm. The gain-bandwidth product of the self-cascaded SHG and SFG processes decreases drastically as the bandwidth is broadened.