This paper shows a novel design for a true zero-order wave-plate to introduce an accurate phase retardation with a big birefringent crystal. The true zero-order wave-plates can be processed with different angles deviating from the crystal’s axis, and the thickness could be selected from millimeter to centimeter order, which increased the mechanical strength greatly. The true zero-order wave-plates were made of NH<sub>4</sub>H<sub>2</sub>PO<sub>4</sub> (ADP) crystal, including half wave-plate (HWP) and quarter wave-plate (QWP). When the cutting angle θ is 4<sup>o</sup>, the thickness d of 1064 nm TZ half wave plate (HWP) is 2.75 mm. At the room temperature (25°C), its extinction ratio as the polarization rotator reaches 1000:1 at 1064nm by using spectroscopic method. With ADP-QWP, a 18.6 ns pulse output of Q-switched Nd:YAG laser (1064nm) is successively realized. When the static energy is 160 mJ, the dynamic energy reaches 113 mJ. The above contents provide not only good references for wave-plates fabrication of other birefringent crystals, but also more potential applications in largediameter optical systems such as ultra-high power laser, high resolution inspection equipment and astronomical observation equipment with a large-diameter ADP wave-plate.
YCa<sub>4</sub>O(BO<sub>3</sub>)<sub>3</sub> (YCOB) was found to have a large temperature bandwidth in XZ optical principal plane. By considering the thermal rotation effect, the temperature bandwidth in spatial directions were studied by theoretical derivation and frequency doubling experiments. The temperature bandwidth in maximum effective nonlinear optical coefficient (<i>d</i><sub>eff)</sub> direction was not as big as that in (30.8°, 180°) direction. The light propagate in the second quadrant was found to have bigger temperature bandwidth than the first quadrant. And the temperature bandwidth was found to change as the wavelength change of fundamental frequency light.