Multistage Phased Electro-Optical Planar Arrays for the Manipulation of High Power Laser Beams

A new type of low-voltage planar electro-optical device for fast beam deflection is reported. It contains two EO modulators, both working as multimode waveguides. The geometry of the waveguides ( ratio height to length) enables an efficient self-imaging of the entrance Gaussian mode. The EO modules are from LiNbO3:MgO with the thickness of 32 mu m, length 9.75 mm, and width of 26 mm. The second stage works as an active phased array with 16 channels. The design provides a flat wavefront at the exit of the system despite the discrete phase shifts in the array channels. This makes a high steering resolution and optical efficiency possible. The full angle deflection range is of +/- 32.(1.27 lambda/D) by using of very low control voltages of 10 - 15 V. The voltages can be further reduced down to 5 V through constructive improvement of the EO-modules. The deflection range can be increased 16 times implementing a 3(rd) EO stage with a 16-channel EO-array. The deflector provides random access to the available angle states. The access time is limited generally by the capacity of the EO modules. It is of only about 0.1 nF in the reported design. We estimate that thanks to the low control voltage and electrical capacity of EO-modules a switching frequency of about 100 MHz may be possible with an advanced electronics. A relatively large face cross-section of about 1 mm(2) will allow using the system with high power lasers and short pulse duration.