Angular non-critical phase-matching second-harmonic-generation characteristics of RECOB (RE = Tm, Y, Gd, Sm, Nd and La) crystals

Abstract

For the first time, the angular non-critical phase-matching (A-NCPM) second-harmonic-generation (SHG) characteristics of a family of monoclinic oxoborate crystals, RECaO(BO) (RECOB, RE = Tm, Y, Gd, Sm, Nd and La), were comprehensively investigated. For all of the realizable A-NCPM SHG styles, the feature parameters including PM wavelength, angular, wavelength and temperature acceptance bandwidths, have been derived from the theory and verified by the experiments. We discovered that the closer the ion radius between RE and Ca, the smaller the birefringence, and the better the A-NCPM SHG properties. As a result, for the Type-I SHG on Y-axis which has the largest effective nonlinear optical coefficient (d) among the three realizable A-NCPM styles, NdCOB crystal presents the longest PM wavelength (927 nm), the largest angular acceptance bandwidth (Δθ⋅l = 84.3 mrad·cm, Δϕ⋅l = 58.8 mrad·cm), and the broadest wavelength acceptance bandwidth (8.7 nm). This discovery will contribute to the design of new NCPM materials, at the same time the parameter formula will be helpful for the theoretical prediction of NCPM performance.

Widely Tunable Angular Non-Critical Phase-Matching Wavelengths from 0.72 to 1.42 μm Based on RE1xRE21−xCOB Mixed Crystals

“…Afterward, the same results were also found in another three series of RE1 x RE2 1−x COB mixed crystals, i.e., Lu x Gd 1−x COB, Sc x Gd 1−x COB, and La x Y 1−x COB [22][23][24]. In 2017, we discovered that RECOB (RE = Y, Gd, La, Tm, Sm, and Nd) crystals were found to possess a wide birefringence range of 0.0425~0.0279 [25], therefore, in theory, the A-NCPM SHG wavelengths might be changed dramatically for their mixed crystals RE1 x RE2 1−x COB (RE1, RE2 = Y, Gd, La, Tm, Sm, and Nd), which showed the possibility of a widely tunable A-NCPM waveband.…”

“…Figure 1 exhibits the dependencies of the ionic radius of RE 3+ on the birefringence, which can be defined that the lesser the difference of ionic radius between the RE 3+ and Ca 2+ ions, the smaller birefringence for RECOB crystals. The theoretical derivation had demonstrated that the A-NCPM SHG wavelengths were in inverse proportion to the birefringence at the fundamental laser, that is to say, the smaller crystal birefringence would generate the longer A-NCPM SHG wavelength, which had been proved in our previous work [25]. The intrinsic factor is the difference in radius between the RE 3+ and Ca 2+ ions in RECOB crystals, rather than the simple radius of RE 3+ ions.…”

High-efficiency broadband second-harmonic-generation of YCa4O(BO3)3 crystal

“…For YCOB crystal, its A-NCPM, T-NCPM SHG properties have been researched previously. [12][13][14] As far as we know, this is the first time that the S-NCPM SHG performance of YCOB is reported.…”

Angle-Multiplexing Nonlinear Holography for Controllable Generations of Second-Harmonic Structured Light Beams

“…However, the phase mismatch becomes Δk 1 (z) Δk 2 (z) ≠ Δk 3 (z), which cannot be simultaneously compensated in a traditional BPM crystal. Here, we propose A-NCPM to solve this problem [36]. A-NCPM is a popular phase-matching configuration, in which the input field generally propagates along the optical principal axis of nonlinear crystal.…”

“…By use of A-NCPM scheme, the conversion efficiency of the SHG process can be well maintained even the input fundamental beam is tilted by a certain angle. Figure 1C compares the normalized SHG conversion efficiencies of BPM and A-NCPM at different incident angles [36,37]. In a traditional BPM process, the angular acceptance bandwidth is typically less than 0.1 °.…”