Title : Laser direct writing of nonlinear photonic crystals and their applications in nonlinear frequency conversion
Artificial microstructures with periodic modulation of second-order nonlinear susceptibility χ(2), also known as nonlinear photonic crystals (NPCs), can compensate phase mismatch in nonlinear optical frequency conversion process by providing additional reciprocal lattice vectors. This quasi-phase matching (QPM) technique thus facilitates efficient nonlinear frequency conversion. Owing to the ability to generate and manipulate light fields at new frequencies, NPCs are widely utilized in fields such as nonlinear optics and quantum information processing. The most prevalent type of NPC is a periodic domain structure in a ferroelectric material, which is typically fabricated by applying an external electric field through patterned electrodes. However, this electric field poling scheme lacks flexibility and is incapable of producing three-dimensional NPCs.A potential solution is to use light field to define domain structures instead of physical electrodes. Recent advancements have been made through direct reversal of ferroelectric domains using focused femtosecond laser pulses, leading to a breakthrough in the experimental fabrication of three-dimensional NPCs. This presentation will begin by briefly introduce the fundamentals of quadratic nonlinear optics, including phase mismatch, QPM and NPCs. Then the common fabrication and characterization methods of NPCs will be given and compared. Subsequently, the research progress and working principles of laser directly written NPCs will be reviewed and discussed. Several application examples will be provided, including domain induction and erasure in PbTiO3 based relaxor ferroelectric crystals, three-dimensional nonlinear optical frequency conversion and nonlinear beam shaping using NPCs. Finally, the challenges faced by this laser poling technology, the future developments and potential applications will be discussed.
Audience Take Away Notes :
- The audience will gain an understanding of the fundamental principles and research advancements in the field of laser induced ferroelectric domain inversion.
- The laser poling technique presented in this talk provides a practical solution to fabricate three-dimensional ferroelectric domain structures, which is beyond the capacity of other fabrication scheme like electric field poling.
- The laser poling technique, together with laser erasure technique, can improve the fabrication accuracy and obtain nanodomain structures.
- The optically poled three-dimensional domain structures can be served as nonlinear photonic crystals and piezoelectric phononic crystals, which can be used in fields including nonlinear optics and acoustics.