Short-time rapid thermal annealing processes for periodically domain-inverted structures with nearly straight domain walls in proton-exchanged LiTaO3

摘要

Abstract: Short-period domain inverted gratings with considerable inversion depth can be formed on the -z face of LiTaO$-3$/ by proton exchange in benzoic rather than pyrophosphoric acid followed by rapid thermal annealing at temperatures around 540 - 610$DGR@C. This procedure allows the fabrication and characterization of first- second-, and third-order domain- inverted gratings for quasi-phase-matching blue-light generation. Annealing for extremely short time (approximately 6 - 12 s) is crucial for achieving domain-inverted structures with near-straight domain walls and least lateral expansion. Lateral domain expansion can be effectively suppressed by pre-annealing at low temperatures ($LSEQ 480$DGR@C) combined with short-time (approximately 5 s) annealing at high temperatures (approximately 600$DGR@C) allowing to fabricate short-period (approximately 3.7 $mu@m) domain- inverted structures. The mechanism of this pre-annealing process is discussed in relation to the inside-field model proposed by Yamamoto et al. Second-harmonic generation of blue light has been demonstrated in a quasi-phase matching planar waveguide fabricated by short-time rapid thermal annealing. The measured normalized conversion efficiency confirms that good domain-inverted structures have been formed.!9