Coherent 430 D3 is the most complicated laser diode never developed.
There are less then 20 of this units sold world wide.
This laser cost well over the price of a new BMW ( 49'000 USD ).
This laser can be used for holography it has a coherent length over 6 meters.
It use a single mode 860 nm laser diode feeding an external resonant doubling Cavity. The doubling crystal is a deuteried KDP. It was developed in the late 1990s When there were no low cost ways of generating 430 nm laser