Dear All,
We're having more trouble than expected doing an ab initio alignment of a Continuum/Quantel YG681 Nd:YAG oscillator alignment, to obtain lasing. This oscillator configuration was used in a number of 1990s to early 2000s Quantel and Continuum Nd:YAG systems (e.g. YG660, NY80, NY82) and perhaps a little later. We're hoping for some helpful tips here.
We proceed by sending a HeNe beam through the center of the rear reflector. We send the alignment beam through the center of the in-place Pockels cell and do angle tuning of the Pockels cell through crossed polarizers to obtain a cross pattern. Then the Nd:YAG oscillator cell is placed such that the HeNe beam passes through center axis. Finally, the output coupler is positioned such that the HeNe spot goes through the Gaussian output spot at the center. The reflection off the output coupler is directed back to center axis. All this is is done with the angled linear polarizer elements in place on both ends of the cell. The quarter waveplates are not in place. (Normally there are 3. The two extra ones on either end of the oscillator cell are meant to produce circularly polarized 1064 nm within the cell.) With proper alignment, this should mean that there should be 1064 nm free lasing. However, we don't see any 1064 nm output, even using an IR viewer.
Our first thought was that we weren't really hitting the Gaussian spot on the output coupler; we think now we have a good way of checking this (but suggestions for a better way solicited). Another plausible possibility seems to be with the slightly wedged output coupler--that we're sending back the HeNe spot that comes from the outer side instead of the inner side. In any event, a procedure we thought would be very easy to accomplish turns out (at least in our hands) not to be. Are there any other plausible errors here? Does anyone have a good procedure, particularly one used for this particular oscillator or one of its near-contemporary first cousins?
Thanks and cheers!
Mark Sulkes
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