In order to obtain maximum conversion efficiency, angle tilting is normally used to reach phase-matching direction. There are two axes for tilting crystals as shown in the right hand figure. Because the NLO crystals supplied by Scitec Instruments are normally cut in a principal crystal plane, conversion efficiency isn't sensitive to the angle tilting around the n-axis. However, it is very sensitive to the angle tilting around the m-axis which is called the tilting axis of NLO crystals and is normal to the marked surface (see Figure). Users need to pay great attention when rotating the crystal around the m-axis. A crystal mount with angle accuracy of about 5 arc per second is recommended.