1.1.4 BBO E-O Q-switched laser

BBO crystals have excellent physical and optical properties. E-O switches made of BBO crystals have the advantages of high extinction ratio, high damage threshold, low absorption loss and small piezoelectric ringing effect, and are widely used in high repetition frequency laser system. The BBO E-O Q-switch realizes the modulation of the refractive index of the crystal based on the lateral electro-optic effect. Therefore, the driving voltage can be effectively reduced by changing the aspect ratio of the BBO crystal. At present, the BBO Pockels cell developed by WISOPTIC Technology in China has a maximum repetition frequency of 1 MHz.

In 2003, someone used part of the laser diode end-pumped Nd:YVO₄ slab to reduce the thermal load of the laser crystal, and used BBO crystal for E-O Q-switching. When the repetition frequency is 10 kHz, the laser output with single pulse energy of 5.6 mJ and pulse width of 6.5 ns is obtained; when the repetition frequency is 50 kHz, single pulse energy of 1.66 mJ and pulse width of 11.3 ns is obtained.

In 2008, another research team also used a partially end-pumped mixed-cavity Nd:YVO₄ slab to obtain a single-pulse energy of 1.2 mJ and a pulse width of 9.5 ns when the repetition frequency was 25 kHz. The experimental results show that there is still much room for improvement in the output laser parameters. The schematic diagram of the E-O Q-switching device is shown in Figure below.

In 2017, researchers used 888 nm end-face pumping Nd:YVO₄ and BBO E-O switch for E-O Q-switching, and obtained 500 kHz high repetition frequency laser output.