#FacesofPhotonics: PhD Student Researcher, Brandon Hellman

ACTION MAN: Brandon in the lab working on a lidar system

Meet Brandon Hellman, this week's SPIE Faces of Photonics series feature. He is a student researcher at the University of Arizona, pursuing a PhD in Optical Sciences. Brandon and his colleagues work on making new lidar systems in Professor Yuzuru Takashima's lab. You can see a sample of their work on the College of Optical Sciences' YouTube page.

Enjoy the interview with Brandon!

1. Share your favorite outreach or volunteer story. 

Laser Fun Day is an annual optics outreach event put on by the Student Optics Chapter "SOCk" in the College of Optical Sciences. The event is free and open to the public, encouraging hundreds of children and adults of all ages to explore optics through hands-on demos put on by undergraduate and graduate students and faculty in the college. 

Demos include a laser maze -- Mission: Impossible-style -- a six-foot-long kaleidoscope, laser radios, solar telescopes, meter-wide Fresnel lenses that melt lava rocks into obsidian, infrared cameras, and many other tools and toys that illustrate different applications and properties of light. 

Star Wars taught us the best way to approach optics and photonics outreach, but instead of a Death Star, we have a new tool: “Now witness the firepower of this fully armed and operational [sun + 4ft Fresnel lens to melt lava rocks into obsidian] station! Fire at will, Commander!” 

FIRE AT WILL!: Running the "lava rock melting station" at Laser Fun Day

2. Explain your current research and how it impacts society. 

I was driving in my friend’s new car on the highway, and just as he was about to change lanes, another car sped up from behind, right into his blind spot. Instead of a sad ending, his new car beeped to let him know a vehicle was there. Unlike traditional cameras, lidar systems capture distance information, scan surroundings, and report a 3D map to a computer. 

In the Takashima Lab, we are working on making lidar systems smaller and less expensive to help more people stay safe. We are using special timing circuits and pulsed lasers, but the real magic of our system is the Digital Micromirror Device (DMD). It is a type of Spatial Light Modulator used in projectors to create arbitrary patterns of light for projection. You will see them used in 3D printing, augmented and virtual reality displays, and active automotive headlights.

Each of the millions of pixels on the DMD is a mirror which rotates between binary "on" and "off" states. All pixels are illuminated so that a pixel in an "on" position will reflect light toward the projection lens to project a white pixel at the projection screen, and a pixel in an "off" position will reflect light away from the projection lens to project a black pixel at the projection screen.

Texas Instruments' 30+ years of development has made the DMD highly reliable and robust, and some DMDs are already automotive-certified. Our lab is stepping in to create a new illumination scheme deviating from industrial norms; but, it's only possible due to the high repeatability of the mechanics of the DMD on the nanosecond scale. 

Our proof-of-concept lidar systems are complete and now we're developing a higher spec system as a stepping stone to automotive commercialization.

3. Share an unexpected discovery you've made in life, either scientific or personal. 

During my first week of grad school Dr. Takashima told me a theory on DMDs that he had, and I told him it was impossible,  my stance being in line with an entire industry. DMDs have always been used as binary devices. The mechanics of the pixel mirrors are designed to flip at kilohertz rates, but most of the oscillation period is in a landed state.

We tested it out anyway, and in a few weeks proved the basis of a family of technologies we’re still developing today, three years later. Our lab is exploring the 48-degree angular extent (after reflection) between the "on" and "off" states. We illuminate the DMD with an eight-nanosecond laser pulse during the transition of the DMD pixels.

Since the 2.4 microsecond transition is almost three orders of magnitude longer than the eight-nanosecond laser illumination pulse, the mirrors are effectively frozen at a particular angle set by our programmable precision synchronization electronics (250 picosecond sync resolution). 

We've turned the DMD into a programmable, wide-angle, high-speed beam steering device. It shattered my perception of the word impossible, so now, instead of "impossible," I just say “pretty difficult.” 

PRETTY DIFFICULT: Brandon scales a wall at Mount Lemmon

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