What keeps your average home experimenter from building an optical clock is the fact that femtosecond combs are still way too expensive and exotic. Some progress has been made -- you can get them from ThorLabs, for instance ( https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=11... ) -- but they are still in the "Call for pricing and lead time" category.
Once optical comb sources are commoditized to the extent that solid-state lasers are now, a lot of fun stuff will become possible.
Heh, I would not ever have expected to see my company mentioned on HN. I'm the software tech lead at Menlo Systems, we're building those frequency combs that Thorlabs sells.
Re the commoditization: Part of the problem is that customers, especially the scientific ones, don't want "commodity" frequency combs. Nearly every comb we sell is tailored to the specific customer in one way or another.
Industrial customers start to be interested in frequency combs more and more. I guess this will be the clientele that values off-the-shelf products more, eventually paving the way for commoditization.
The presence of individuals such as yourself is what makes the HN comments such a frequently meaningful place to find insightful discussions. Thanks for the context!!
Once optical comb sources are commoditized to the extent that solid-state lasers are now, a lot of fun stuff will become possible.