The RISTRA OPO is not currently offered for sale by AS-Photonics.
The RISTRA is an image-rotating nanosecond optical parametric oscillator (OPO) designed to produce excellent beam quality in high energy pulses. The non-planar optical path (shown in the right figure above) introduces a 90° rotation of the resonated signal beam on each pass of the cavity. This has been proven to produce high beam quality and high pointing stability. Image rotation also allows fixed mirror mounts, so no mirror adjustment is ever needed. The left figure shows the single-crystal RISTRA assembly previously offered by AS-Photonics.
We've also spent quite a lot of time developing quality documentation (see the RISTRA manual).