Optical Coherence Tomography

How Our Frequency Shifters Become Known for The OCT Market

Hello there! Welcome to my first Brimrose Blog. My name is Mark, and I’ve been a test engineer here for about 20 years. If I am being a bit informal, I am new to “blogging,” so please excuse me. If you are new to Brimrose, or “acousto optics,” I’ll try to enlighten you a bit as to what we do, and why people pay for it. So, as my mother asks me, “what do you do?” Basically, we help our customer manipulate light. Well, that’s fine you say, but what good is it? That turns out to be a rather interesting question, especially if you have a heart…

About ten years ago, a U.S. research hospital ordered some frequency shifters. A frequency shifter slightly changes the frequency of the light going through it; another way of looking at frequency shifting is frequency shifters change the color of the light passing through them toward more blue (upshift) or more red (downshift.) A short while later, the same research hospital ordered some more units; well, good, I thought, a repeat customer. Then a Japanese company, at the time obscure to us, ordered similar frequency shifters, but fiber pigtailed units rather than free space shifters. The US research institute would order some, then the Japanese company would order some, and the pattern would repeat; the amount of frequency shift would sometimes vary, but otherwise the specifications were always pretty similar. A few years ago, the US research hospital’s orders dwindled… but the Japanese company’s orders jumped, big time, to orders of over a hundred at a time. It was clear that something big and serendipitous was happening, and we are excited to be part of it. Turns out, the Japanese company, a supplier to worldwide medical markets, and the US research hospital were developing the same thing, Optical Coherence Tomography (OCT), for looking at the tissue and plaque around blood vessels.

Simply put, OCT is a technique for obtaining sub-surface images. It does not use radiation, which is a major plus. It is effectively a type of “optical ultrasound,” providing imaging reflections from within tissue to provide cross-sectional images. Its resolution can be 10 microns, better than other imaging processes such as MRI. It is filling an important gap between cellular imaging and tissue and organ imaging.

I suppose you are saying, “But weren’t you talking about frequency shifters, how do they fit into Optical Coherence Tomography?”’ Well, frequency shifters are a major component of interferometers, devices where a beam of light is split, made to go to different paths, and then recombined. The light is affected by its journey, and the recombined beams “interfere” with each other, giving a picture of where they have been, be it through the air of a laboratory, or the plaque of someone’s arteries.

Neither I, nor anyone at Brimrose, initially realized what problem those first frequency shifters were being applied to, nor that that they would eventually lead to large orders from the Japanese customer. Supplying large quantities of devices for medical uses has had its challenges. Demand for a high degree of consistency, low outgassing, RoHS compliance, materials and processes tracking and documentation have been some of the useful headaches the journey has given us.

Brimrose has other interesting technologies, which is why I stay around, that could have similar potential medically or otherwise beneficial applications. A Brimrose core technology is acousto-optic tunable filters which operate from the UV well into the near-IR range. Optical switchingOptical ‘tweezers.’ More on those later, maybe, if there is interest.

I think our willingness to work with customers to the specifications they desire is a key characteristic of Brimrose’s and has helped us in this journey. If you would like to know more about our frequency shifters, you can call at 410/472-7070.