Lasers! Octave Photonics Makes Computer Chips for Light

John Himes

January 8, 2023

We’re in the middle of a revolution that’s as big as the advent of integrated electronic circuits, and Octave Photonics is at the forefront. Just like electrical transistors paved the way for today’s digital technology—especially the computer—today’s photonic integrated circuits (PICs) are an emerging technology with massive implications.

These chip-based waveguides are highly customizable, enabling scientists and engineers to do things with light that can’t be done with conventional fiber optics. The main applications for Octave’s PICs involve advanced laser systems, such as a kind of optical measuring tool called a frequency comb, but that’s just the beginning.

These chips have tons of uses. From building quantum computers to optimizing traditional computing architecture for I/O throughput, we’re just starting to see what this next-generation hardware is capable of.

Octave Photonics specializes in a nonlinear nanophotonic capability called supercontinuum generation. Dr. Daniel Hickstein, the company’s principal scientist, likens this process to “tiny rainbow lasers.”

What does this all mean? And how does Octave Photonics fit into Colorado’s advanced technology ecosystem?

You’ll have to keep reading to find out!

Octave Photonics under the spotlight

In their lab in Louisville, Colorado, Octave Photonics creates nanophotonic chips, which are similar to microelectronics chips, except they replace electrical transistors with pathways for light. Their product lineup features devices that utilize nanophotonic chips to control light.

On its own, it may not seem like much more than a useful tool. But when we start to consider the implications of this technology—with applications ranging from quantum computing to searching for exoplanets in faraway solar systems—we see that Octave is building more than just a better ruler for measuring light. They’re unlocking potential for technology yet to be built and truths yet to be discovered.

At the same time, they’re a small and humble company that doesn’t daydream of world domination. They maintain a sense of humor. “Our high-tech lab is a storage closet in the basement of a dentist’s office,” says Dr. Zach Newman, a cofounder and physicist. “And we want to continue to grow the business in an incremental and sustainable way.”

This gives them the freedom to follow their interests, take on curious side projects, and enjoy the process of developing bleeding-edge hardware.

Let's talk lasers and applications

Starting with the big picture, Octave Photonics researches and manufactures packaged and ruggedized devices based on nanophotonic chips. The underlying technology has been in use in academic labs for several years. Their main innovation is bringing it to market in a form factor that’s plug-and-play and not as fragile.

So far, their devices serve as subcomponents for larger optical systems, such as portable frequency comb lasers. “Right now, we’re like a screw manufacturer,” says Dr. Hickstein, likening their hardware to a component that can then be used to build any number of machines. “We don’t know the full extent of how people are going to use it.”

Application agnosticism aside, they are able to point to some specific use cases that their hardware is already seeing. When I visited, they showed me a device they were about to ship to the Mauna Kea Observatory in Hawaii.

Astronomers who want to find exoplanets, for instance, need to track minute changes over a wide band of light wavelengths to detect small Doppler shifts that indicate a planet orbiting a distant star. They can use Octave’s devices to calibrate their spectrometers and take better readings.

Optical atomic clocks are another key application. An optical atomic clock consists of a laser which has its frequency locked to some type of atom, often ytterbium, rubidium, or strontium. The precise frequency of this laser serves as the pendulum for the clock.

Of course, a clock requires more than a pendulum to function; it needs the clockwork that keeps track of the pendulum’s ticks. For an optical atomic clock, this takes the form of an optical frequency comb. Octave’s devices, based on photonic integrated circuits (PICs), allow manufacturers to more easily construct frequency combs that are lighter and cost less.

This paves the way for portable optical atomic clocks, which have important applications in next-generation navigation systems similar to GPS.

This is only beginning to scratch the surface of the applications for frequency combs, and other applications are emerging rapidly. For example, many quantum computers rely on precision frequencies to probe atomic transitions, requiring optical frequency comb systems. Telecommunication applications include faster and better long-haul communications.

LongPath, another Colorado company, uses frequency combs to sense airborne methane and monitor emissions from large-scale oil and gas operations.

In addition to these practical applications, Octave Photonics isn’t afraid to take on interesting side projects with massive potential. Over the past year, they’ve worked closely with Dr. Carver Mead, professor emeritus at Caltech, providing a testbed for him to run experiments to support his theory of gravitation with four vector potentials (G4v).

If Dr. Mead is right, advances in instrumentation may be the key to a new foundational physics theory that contradicts some aspects of Einstein’s theory of general relativity. Octave Photonics is helping to develop some of the instruments needed to test this theory.

Technology deep dive

If you’re a nerd like me who’s often frustrated by the lack of technical details in feature articles like the one you’re reading, this section’s for you.

Let’s start by going over some key terms.

Nanophotonics takes optical systems and shrinks them down to a tiny scale, so that they can become photonic integrated circuits (PICs) “Creating these chips is a very similar process to creating silicon electronics,” says Dr. Newman. Just like Intel designs and fabricates electronic integrated circuits, Octave uses deposition, lithography, and etching processes to create PICs.

Nonlinear photonics is a branch of optical science and engineering that studies how multiple photons combine when we pack a lot of them into a small area (a high intensity pulse) and shoot them at a material.

In this case, linearity doesn’t refer to the path of the light itself; it’s a feature of the underlying mathematics that describes the relationship between the material’s polarization density and the light’s electric field. A linear response corresponds to simple interactions of light with matter that we see every day, like light bending as it passes through a lens or a water glass.

Octave Photonics is after nonlinear responses. For instance, their chips can combine the energy of multiple wavelengths of light into a single new wavelength. Nonlinear optical phenomena such as four-wave mixing are at the heart of supercontinuum generation, explained below.

“Nonlinear optics never occurs in nature,” says Dr. Hickstein. Only by using high-intensity femtosecond laser pulses with carefully selected materials can the Octave team create the nonlinear responses they’re after. These physical phenomena are the bedrock of their technology.

Supercontinuum generation is a specific type of nonlinear response that produces a huge range of frequencies. “The light that comes out from these devices has a continuously broad spectrum,” says Dr. Newman. “You allow the material to help you convert extremely high-intensity light at a narrow bandwidth into an extremely wide bandwidth.”

As opposed to a prism, which takes white light and breaks it up into its constituent components, a supercontinuum generator uses nonlinear optics to transform a single color of light into many colors.

Putting the physics to work

So now that we have a PIC that uses nonlinear photonics to generate a supercontinuum, what do we do with it?

The first answer to that question is frequency combs, which are devices used to measure the frequency of light waves. While the original technology’s inventors won a Nobel prize in 2005, scientists are only just scratching the surface of possible applications. Use cases continue to grow as the devices become smaller, less expensive, and more capable.

Octave Photonics has scaled them up and commercialized them. In addition to packaging them so they can handle real-world environments outside the lab, Octave’s ability to generate a supercontinuum means their frequency combs can measure much wider bandwidths of light than previous generations.

The PIC-based devices that Octave Photonics makes are a perfect pairing with frequency combs, since they allow these relatively narrow-bandwidth lasers (~20 nanometers) to be broadened to span over 2,000 nanometers. This makes the frequency comb much more useful.

Instead of having a ruler that can only measure green light, for instance, Octave widened the ruler so it can measure light up and down the spectrum. Essentially, the frequency comb provides optical systems with a known reference point that they can calibrate against, much as a ruler acts as a reference for measuring length.

The “teeth” of the comb are just like the ticks on a ruler.

When taking a measurement against a frequency comb, the system needs to know two numbers. First it needs the repetition rate, which is the spacing of the wave’s peaks. But it also needs a baseline, an offset of those peaks from a zero point. This is where the ruler starts. That offset is called the carrier envelope offset (CEO) frequency.

It’s fairly easy to detect the repetition rate, but figuring out the CEO is much more challenging. “The hard part is that you first need to broaden your spectrum to span at least one octave,” says Dr. Hickstein. Just like in musical sound waves, an optical octave is a doubling of a light wave’s frequency.

Dr. Hickstein continues, “People have been doing this for a long time to use frequency combs, but we’re the first to make an easy-to-use device. Traditionally, finding the CEO is very taxing, and a grad student would often burn a few weeks—or even months—in the lab getting it to work.”

Their Comb Offset Stabilization Module (COSMO) is the first commercial CEO frequency detector that’s ready to plug and play. Using specialized PICs allows them to achieve octave-spanning supercontinuum generation with lower input pulse energies. This in turn makes it easier to measure the CEO frequency.

The ability to span an octave—a doubling of frequency—led to their company name, Octave Photonics.

The Octave Photonics story

“Starting a company was an easy decision because people kept asking to buy our chips!” says Dr. Newman when asked about his aha moment. Customers begging to pay you—talk about a great reason to go into business!

At the time, the Octave team members were postdoctoral researchers at the National Institute of Standards and Technology (NIST) in Boulder. Dr. Newman, Dr. Hickstein, and Dr. David Carlson, the company’s other cofounder, were part of a team working on nanophotonics technologies like frequency combs and atomic clocks.

They founded the company in 2019, but the real kickoff was in the summer of 2021.

For Dr. Newman, this represented the realization of a dream he’d carried since childhood. His great uncle, Dr. Joseph Reader, was an atomic spectroscopist at NIST in Gaithersburg, Maryland, and encouraged Dr. Newman to study physics. Dr. Reader also ran a spinoff company out of his home.

“He had a cool lab in his basement,” says Dr. Newman. “He was a mad scientist. I hoped that one day, when he was done with his company, maybe I could buy it from him, and that’s what I’d do with my career.” Dr. Reader sold the company before Dr. Newman finished grad school, but the idea stuck in his head. “I had always been interested in starting a company instead of working as an academic.”

Since the company’s inception, the Octave team has continued to grow and innovate. “We started off working on these nanophotonic chips at NIST, not knowing if supercontinuum generation in waveguides would be practical at all,” recalls Dr. Hickstein.

“But then, a few years later, we were able to use these chips to allow a normally power-hungry frequency comb to run off a small USB battery pack. That’s when I realized that devices based on our nanophotonic chips could make a big difference in the advancement of frequency comb technology.”

As their sales have increased, they’ve refined their manufacturing processes, brought on Dr. Cecile Carlson (senior optical engineer) and Dr. Grisha Spektor (senior photonics engineer), and released new products like the COSMO. “We’re making the products that we wished existed when we were in the lab at NIST,” says Dr. Hickstein.

Going forward, their biggest challenge is knowing exactly what direction to take next. Like most startups, figuring out where to invest their resources and plan that strategic roadmap is hard. “Do we work to make our current products less expensive and more capable, or do we move on to the next technology?” asks Dr. Hickstein.

As they scale up, they want to make sure they’re running a sustainable business that helps people move science and technology forward while providing opportunities for local talent.

Tech collaboration in Colorado

Octave Photonics was born in Colorado and continues to be a key player in the local scene.

Of course, NIST is at the heart of it all. Not only did the team first meet there, but they continue to collaborate with their postdoc advisors: Dr. Scott Papp, Dr. Scott Diddams, and Dr. John Kitching. The connection to NIST is still strong. When I went to visit Octave’s labs, Dr. Carlson was busy at NIST working on a project with postdocs in Dr. Papp’s group.

As Dr. Poolad Imany, founder and CEO of Icarus Quantum, said in his company’s Colorado Tech Spotlight, “NIST is an open entity that benefits everyone.” Dr. Imany knows the Octave Photonics team from their mutual connections at NIST.

The Octave team also points to CU and JILA, a joint institute of CU Boulder and NIST, as other key public sector collaborators.

They also work in collaboration with local private companies. For instance, they’re currently developing a portable, ruggedized atomic clock in conjunction with Vescent and Infleqtion. Together, they’re aiming to reduce today’s room-sized optical atomic clocks—think old-school mainframe—into something that fits into a backpack.

As the Colorado tech ecosystem grows, there will be even more opportunities for Octave Photonics. For instance, Colorado was recently designated as part of a Quantum Tech Hub called Elevate Quantum, and most quantum technologies rely on precision laser systems. Octave’s nanophotonics devices are a key component in many of those systems.

At the same time, they also rely on high-tech suppliers in the area. One key vendor is Base16 Tech, a CNC machining, electrical engineering, and software development firm in Johnstown. Whenever they need help designing and fabricating hardware, especially the packaging for their PICs, they call up Base16 Tech.

Last but certainly not least, Octave Photonics also benefits from the local photonics scene, especially the Colorado Photonics Industry Association. “They provide a great service for the local photonics community,” concludes Dr. Hickstein. “Their events are great for a small company like us, since it gives us the opportunity to interact with people from other local companies, universities, and national labs.”

In the end, that’s what it’s all about for Octave Photonics: pushing science and tech forward, enjoying the process, and contributing to the local tech community. They couldn’t have picked a better place than Colorado.

About the Colorado Tech Spotlight

The Colorado Tech Spotlight highlights local innovations and the stories behind them. The series explores how the Colorado tech ecosystem creates an environment that promotes technological progress.

It is produced by Dynamic Tech Media and written by John Himes. Photography provided by Kort Duce.