I think the key to this concept is an optical comb filter. Archita Hati of the Phase Noise measurement Group at NIST has been researching ultra low phase noise 5MHz references using an optical standard and comb filter as well as extensive RF components to down converting to the desired frequency. In experiments I believe she has achieved phase noise better then -154db @ 1Hz offset. It does appear to be the future but currently is far to large and complex for most if any practical use. I believe this link is the paper by Archita Hati I referred addressing State-of-the-Art RF Signal Generation From Optical Frequency Division. http://tf.boulder.nist.gov/general/pdf/2646.pdf Enjoy; Thomas Knox
Thomas Knox > From: [email protected] > Date: Wed, 14 Jan 2015 07:00:09 +1100 > To: [email protected] > CC: [email protected] > Subject: Re: [time-nuts] Current state of optical clocks and the definition > of the second > > > THe stability /accuracy of lasers is entirely dependent on the cavity length. > Materials used are usually invar or silica, so you are no better off than > with a quartz crystals. > They are just a resonant cavity. > cheers, > Neville Michie > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
