Highly sensitive ultrasound detection using nanofabricated polymer micro-ring resonators

Youngseop Lee, Hao F. Zhang, Cheng Sun*

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

4 Scopus citations


Photoacoustic (PA) imaging enables noninvasive volumetric imaging of biological tissues by capturing the endogenous optical absorption contrast. Conventional ultrasound detectors using piezoelectric materials have been widely used for transducing ultrasound signals into the electrical signals for PA imaging reconstruction. However, their inherent limitations in detection bandwidth and sensitivity per unit area have unfortunately constrained the performance of PA imaging. Optical based ultrasound detection methods emerge to offer very promising solutions. In particular, polymer micro-ring resonators (MRRs) in the form of integrated photonic circuits (IPC) enable significant reduction for the sensing area to 80 μm in diameter, while maintaining highly sensitive ultrasound detection with noise equivalent pressure (NEP) of 0.49 Pa and a broad detection frequency range up to 250 MHz. The continued engineering innovation has further transformed MRRs to be transparent to the light and thus, opens up a wide range of applications, including multi-modality optical microscope with isometric resolution, PA endoscope, photoacoustic computed tomography (PACT), and more. This review article summarizes and discusses the evolution of polymer MRR design and the associated nanofabrication process for improving the performance of ultrasound detection. The resulting novel imaging applications will also be reviewed and discussed.

Original languageEnglish (US)
Article number30
JournalNano Convergence
Issue number1
StatePublished - Dec 2023


  • Maskless lithography
  • Micro-ring resonator
  • Nano-fabrication
  • Nanoimprint lithography
  • Photoacoustic imaging
  • Soft nanoimprint lithography
  • Ultrasound detector

ASJC Scopus subject areas

  • General Engineering
  • General Materials Science


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