Optical properties of borate crystals in terahertz region

Observation of a different birefringence order at optical and THz frequencies in LBO crystal

“…producer as for the previous study [8], the Institute of Geology and Mineralogy SB RAS, Russia [4]. It was found that the birefringence order at THz frequencies was in agreement with that at optical frequencies -i.e.…”

“…It was found that the birefringence order at THz frequencies was in agreement with that at optical frequencies -i.e. n x < n y < n z -and was therefore contrary to n z > n x reported in [8]. It was suggested that the result observed in [8] was occasioned by mistaken axis labeling.…”

“…n x < n y < n z -and was therefore contrary to n z > n x reported in [8]. It was suggested that the result observed in [8] was occasioned by mistaken axis labeling. Moreover, the 40 largest measured birefringence was n z − n x = 0.42, rather than 0.35 as reported in [8], which was ascribed to failure to observe the highest refractive index.…”

“…Some reflectivity and absorption spectra were published for 50-25 1800 cm −1 in [7]. Antsygin et al [8] reported only two well-resolved dispersion curves (n x and n z ) as well only two absorption spectra (α x and α z ), omitting the data for the Y -axis, apparently due to the low resolution of the available THz-TDS system. The relationship n z > n x was found to be reverse to that seen in the visible.…”

“…It was suggested that the result observed in [8] was occasioned by mistaken axis labeling. Moreover, the 40 largest measured birefringence was n z − n x = 0.42, rather than 0.35 as reported in [8], which was ascribed to failure to observe the highest refractive index. The larger birefringence is particularly important because it places LBO amongst nonlinear crystals where phase matching is possible for down-conversion into the THz band.…”