Jui-Yu Lai

Engineered multiwavelength conversion using nonperiodic optical superlattice optimized by genetic algorithm

Nonperiodic optical superlattice for multiwavelength conversion with flexible spectral distributions is optimized by genetic algorithm using two target functions sequentially. The overall conversion efficiency could be higher than that of aperiodic optical superlattice by 14%.

Healing-block-assisted quasi-phase matching

A new QPM structure is proposed to improve the efficiency when the first-order QPM domain length is too short to be fabricated. SHG efficiency 4.69 times higher than the third-order QPM is experimentally demonstrated.

Phase-matching spectral phase measurement and domain period reconstruction of aperiodic quasi-phase matched gratings by nonlinear spectral interferometry

We experimentally measured the phase-matching spectral phases of aperiodic quasi-phase matched gratings for the first time (to the best of our knowledge) by nonlinear spectral interferometry. The retrieved information is useful in determining the temporal shape of the nonlinearly converted ultrafast signal and reconstructing the slowly-varying domain period distribution. The method is nondestructive, fast, sensitive, accurate, and applicable to different nonlinear materials. Compared to taking microscopic images of the etched crystal surface, our method can directly measure the domain period distribution in the crystal interior and is free of the artificial random duty period error due to image concatenation.

Broadband mid-infrared polarization rotator based on optically addressable LCs.

This work proposes a mid-infrared polarization rotator that incorporates a twisted nematic liquid crystal (TNLC) cell with a photo-controllable alignment layer. The TNLC device with a sufficient phase retardation can act as an achromic polarization rotation device over a wide wavelengths range and thus can rotate the polarization of a mid-IR laser beam. The photo-alignment technique enables TNLCs with arbitrary twisting angles to be generated by the use of visible polarized addressing light to control the directors of the photo-alignment layer. Therefore, arbitrary rotation angles of the polarization axis of a linearly polarized mid-IR laser beam can be realized. Moreover, the rewritable property and reliability of this polarization rotator are experimentally verified. The flexibility of polarization control for broadband mid-IR opens up a large range of potential mid-IR applications.

Engineered quasi-phase matching for conversion efficiency optimization of coupled χ (2) processes

We propose an algorithm to optimize the efficiency of coupled χ(2) processes in an aperiodic optical superlattice. Frequency tripling efficiency 33% higher than the limit of sequentially periodic structure is numerically demonstrated for the first time.

Generation of 30 mW CW ultraviolet by a two-path geometry for cascaded χ (2) processes with periodically poled lithium niobate crystals

30 mW continuous wave ultraviolet radiation is generated via a two-path geometry for cascaded frequency doubling and sum-frequency generation (SFG) at 18.9 W pump, where SFG is enabled by a third-order periodically poled MgO:LiNbO3.

Measurements of phase-matching spectral phase and domain period distribution by nonlinear spectral interferometry

Phase-matching spectral phases of aperiodic quasi-phase matched gratings are experimentally measured by nonlinear spectral interferometry and microscopic images, respectively. The former enables accurate reconstruction of domain length distributions with 810-μm resolution.

Healing block-assisted quasi-phase matching

A new QPM structure is proposed to improve the efficiency when the first-order QPM domain length is too short to be fabricated. SHG efficiency 4.69 times higher than the third-order QPM is experimentally demonstrated.

Arbitrary complex phase-matching spectral grid designed by iterative domino method

We designed complex phase-matching spectral grid by iterative domino algorithm, and analytically proved that it can achieve the maximum conversion efficiency. Experimentally measured conversion efficiencies agreed well with the numerical results.

Nonperiodic optical superlattice optimized by genetic algorithm for engineered multiwavelength conversion

We experimentally demonstrate engineered multiwavelength conversion using nonperiodic optical superlattice optimized by genetic algorithm with two target functions. This scheme has better spectral shape fidelity and ∼15% higher conversion efficiency compared to aperiodic optical superlattice.