Global Maxima of the Acousto-Optic Effect in CaWO₄ Crystals

Abstract

The global maxima of the acousto-optic interaction are theoretically determined for CaWO4 crystals by extreme surfaces method. As it is shown, the highest value of the acousto-optic figure of merit M2 is equal to 14.0 × 10 −15 s 3 /kg and achieved in the case of the diffraction of ordinary or extraordinary light beam on the slow quasi-transversal acoustic wave. At that the incident light wave propagates close to c-axis of the crystal and the corresponding acoustic wave propagates in the direction close to the perpendicular one.

Розповсюдження Акустичних Хвиль У Кристалах Вольфрамату Кальцію

“…The experimental study of the shear angles of acoustic waves was carried out in the framework of the shadow method (the Tepler method) [9]. In the course of experiments, the acoustic beam was initially generated in a buffer (a Bragg cell), the light and sound conductor of which was made of fused SiO 2 .…”

“…Crystals of calcium tungstate CaWO 4 with the scheelite structure (the symmetry class 4/m) are a well-known material for applications in the scintillation [1,2] and luminescence [3,4] dosimetry, optoelectronic devices [5,6], and lasers [7,8]. At the same time, on the basis of the studies of the piezoelectric, elasto-optical, and acousto-optical characteristics of CaWO 4 crystals, which were performed in works [9,10], a conclusion can be drawn that this material is promising for its application in acoustooptical devices, in particular, operating in the ultraviolet spectral range (up to 130 nm). For instance, according for the estimate made in work [9], the value of the acousto-optical figure-of-merit for this material is 𝑀 2 = 14.0 × 10 −15 s 3 /kg, which is comparable with the theoretically achievable maximum value 𝑀 2 = 15.9×10 −15 s 3 /kg for lithium niobate and is almost an order of magnitude higher than the 𝑀 2 -value for quartz.…”

“…However, a detailed analysis of the features of the AW propagation has not been carried out yet for CaWO 4 crystals (the calculations made in work [9] included the determination of the velocities and shear angles, but they did not have a general nature from the viewpoint of describing the acoustic properties of the crystal). Therefore, in this work, we theoretically calculated the propagation velocities of acoustic waves, their shear angles, and diffraction divergence in CaWO 4 crystals.…”

Глобальні Максимуми Та Оптимальна Геометрія Акустооптичної Взаємодії У Кристалах Тригліцинсульфату

“…Однак, дослідження, проведені у [17], не вичерпували всіх можливих геометрій акустооптичної взаємодії (просторових розташувань хвильових векторів та напрямків поляризацій взаємодіючих світлової та акустичної хвиль). Метою даної роботи є визначення найбільшої теоретично досяжної величини коефіцієнта M 2 для кристала TGS та відповідної йому геометрії взаємодії, для чого застосовується метод екстремальних поверхонь, розвинутий у роботах [18][19][20][21][22].…”