Short access time acousto‐optic deflector based on two cascaded Paratellurite devices

Acousto‐optic deflectors (AODs) are used in many applications requiring optical scanning devices with various specifications regarding access time, resolution and wavelength. High time‐bandwidth products can be achieved with AODs made in a tellurium dioxide (TeO2) crystal. As paratellurite crystals are available with relatively large dimensions, the time‐bandwidth product can be increased by enlarging the optical aperture. However, the access time is increased which is not suitable for random access scanning mode. A new laser scanning system is then presented based on two wide‐band paratellurite acousto‐optic deflectors. Anisotropic interactions take place under two different tangential phase matching (TPM) configurations in such a way that the acousto‐optic bandwidths add up. The optical arrangement of the two cascaded AODs is detailed. The feasibility of such a cascade deflection system has been demonstrated for the green wavelength λ= 514 nm of an argon laser. The total frequency bandwidth is Δft = 100 MHz, equally distributed between the two acousto‐optic deflectors. The total angular scan at the output is Δθt = 4.5 ° leading to more than 120 resolvable spots for a 1 mm truncated Gaussian beam and a short access time (as low as 1.5 μs).