Two-dimensional refractive index modulation by phased array transducers in acousto-optic deflectors

Abstract

Acousto-optic deflectors are photonic devices that are used for scanning high-power laser beams in advanced microprocessing applications such as marking and direct writing. The operation of conventional deflectors mostly relies on one-dimensional sinusoidal variation of the refractive index in an acousto-optic medium. Sometimes static phased array transducers, such as step configuration or planar configuration transducer architecture, are used to tilt the index modulation planes for achieving higher performance and higher resolution than a single transducer AO device. However, the index can be modulated in two dimensions, and the modulation plane can be tilted arbitrarily by creating dynamic phase gratings in the medium using phased array transducers. This type of dynamic two-dimensional acousto-optic deflector can provide better performance using, for example, a large deflection angle and high diffraction efficiency. This paper utilizes an ultrasonic beam steering approach to study the two-dimensional strain-induced index modulation due to the photoelastic effect. The modulation is numerically simulated, and the effects of various parameters, such as the operating radiofrequency of the transducers, the ultrasonic beam steering angle, and different combinations of pressure on each element of the transducer array, are demonstrated.

Dynamic high-resolution optical trapping of ultracold atoms

“…Smoother potentials are achieved using phased array piezoelectric oscillators, shown in Fig. 4(a) (Pieper and Korpel, 1983;Wang et al, 2017). Phased array AODs control the relative phases between the adjacent oscillators to tune θ s , and maintain the nearer to optimal Bragg condition θ 1 ≈ θ 2 across a broader bandwidth ω s .…”

Optimizing linear phased array transducers for non-destructive evaluation of thin layers

“…In the following, use is made of the mathematical formulation based on Fourier approach that was used by Wang et al [20,21] to analyse steering for ultrasonic wave patterns in solids generated by PA transducers. This modelling is appropriate in the situation where the array element is assumed to be in contact directly with a solid through a fluid couplant.…”

“…These can be advantageously represented in Fourier approach by analytic expressions, which enable then their accurate and rapid computation. Using the Fourier approach, Wang et al [20,21] have developed a straightforward model for dealing with the analysis of diffraction that occurs following the emission of ultrasonic waves by PAs transducers. This consists of a simple analytic expression that gives explicitly the displacement field caused by the ultrasonic wave propagation in the tested medium.…”

Engineering time-averaged optical potentials for Bose-Einstein condensates

“…Since deflector applications modulate the di↵racted beam angle ✓ 2 without changing the incident beam angle ✓ 1 , suboptimal di↵raction conditions and powers are achieved for larger angular displacements, where ✓ 2 6 = ✓ 1 . Acousto-optic devices with phase array piezoelectrical oscillators improve the di↵raction e ciency across broader bandwidths by tuning the relative phase between adjacent oscillators [373][374][375][376]. Tuning the oscillator phases steers the acoustic wave through the deflector, maintaining the optimal grating angle; see Figure 3.3(a-b).…”