NIST Shows How to Make a Compact Frequency Comb in Minutes Video Transcript

(back to video)

Scott Papp, NIST physicist:

We've developed a new technique to create micro-resonators, tiny little optical cavities, which can confine light into a very small volume.

These resonators actually have a pretty wide range of uses. So here at NIST we use them for basic optical frequency metrology, we use them as part of a new technique to create very small physical size optical frequency combs.

So an optical frequency comb is a very precise ruler for measuring light frequencies and also for measuring very short optical pulses of light.

And the comb is composed of many, many teeth, OK, so different colors of light. And what's really special is that the teeth are all spaced by an exact amount. So the spacing from one tooth to the next is always the same, and it's always controlled to a very, very high level.

So traditional frequency comb technology has been based on mode-locked, femtosecond — so very short pulse — lasers. But these tend to be sort of tabletop-sized so the whole system takes up a few square feet.

So what we've been working on at NIST is developing frequency comb technology based on tiny little millimeter-scale pieces of glass and only a low-power laser. And when we send that laser into the small volume of glass, a whole range of new frequencies are generated, and that creates the basic form of the frequency comb.

So what you're seeing in this video is really the full fabrication technique.

So we have a piece of this fused quartz glass material, which only costs a few pennies, and it's being held in a very simple lathe. And what we use, what you're seeing now, is the carbon dioxide laser is focused down onto the surface of the glass. And it's actually heating the glass up so much that the material is evaporating away. This is very much like machining metal on a metalworking lathe except we're using the carbon dioxide laser as kind of a tool to shape the glass surface.

And the result is very high "quality factor" microcavities that we can create in under one minute.

So one of the unique aspects of our fabrication technique is the control of the resonator size. And for our work at NIST this means that we can make frequency combs now with a very wide range of spacings. And this is something that's not possible with traditional comb technology. Yeah, so as you see in the video we can make these microcavity devices in less than one minute. And what's really exciting is it only takes us an extra minute after that so start making an entire frequency comb. You know, this could be kind of a frequency standard, but a standard that doesn't have to exist just at NIST. It could get, you know, go outside of the lab to the places that really need to make these kinds of measurements, instead of having to bring them always to NIST.