Researchers Develop a Millimeter-Scale Chip-Based Supercontinuum Source for Optical Coherence Tomography (OCT)
A collaboration between the research groups of Christine Hendon and Michal Lipson has demonstrated a novel supercontinuum source based on a Si3N4 photonic chip for optical coherence tomography (OCT) imaging that provides improved imaging performance compared to the state-of-the-art supercontinuum sources.
Optical coherence tomography (OCT) has become the standard-of-care in medical specialties such as ophthalmology, dermatology, and is an emerging imaging technology in other areas such as gastroenterology and breast cancer imaging. The light source is one of the key elements that determines the OCT performance. Supercontinuum sources for OCT have raised great interest as they provide broad bandwidth to enable high resolution and high power to improve imaging sensitivity. However, they require very high power to achieve broad bandwidth and strong performance, and the spectrum needs to be shaped and attenuated with conventional bulk optical filters, which severely limit their practicality.
The team designed a supercontinuum platform based on a 1 mm2 Si3N4 photonic chip specialized for OCT. This photonic chip can be directly pumped and efficiently generated supercontinuum near 1300 nm without any post-filtering using this chip. They demonstrate imaging sensitivity that would require 100 times more optical power using a state-of-the-art commercial supercontinuum source.
“Silicon nitride is a widely used material in the silicon-based semiconductor industry that is used to build computer/smartphone chips,” Ji notes, one of the lead authors on the paper. “So, by leveraging the capabilities of this mature industry, we can foresee reliable fabrication of these photonic chips on a massive scale at a low cost.”
Dispersion engineering in integrated photonics is more easily achievable which makes the platform suitable for a variety of applications in OCT. For example, spectra centered at 800 nm or 1000 nm can be generated for ophthalmic imaging, spectra at 1700 nm or even longer wavelengths can be generated for imaging industrial materials and dental samples.
“This is the first demonstration of using a spectrum generated by an integrated photonic chip in the field of OCT imaging, with no filtering, and we showcased its capability to generate high quality 3D volumetric data of human tissue. This important result paves the way towards portable OCT and we anticipate seeing other integrated photonics platforms being utilized for biomedical imaging applications.,” says Mojahed, another lead author on the paper.
The team is working on applying such devices to realize a high performance, low-cost, and fully integrated OCT system. In a paper published earlier in APL Photonics, Hendon’s and Lipson’s groups demonstrated some steps towards integrating different parts of systems on the same chip. In cooperation with Columbia Technology Ventures, the team has a provisional patent application and is exploring commercialization of this technology.
The article, "Millimeter-scale chip-based supercontinuum generation for optical coherence tomography," is authored by Xingchen Ji, Diana Mojahed, Yoshitomo Okawachi, Alexander L. Gaeta, Christine P. Hendon, and Michal Lipson. The article appeared in Science Advances on September 17, 2021 (DOI: 10.1063/1.5111164). It can be accessed at: https://www.science.org/doi/10.1126/sciadv.abg8869