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This article reports the fine-tuning of the optical resonance wavelength (ORW) of surface-micromachined optical ultrasound transducer (SMOUT) arrays to enable ultrasound data readout with non-tunable interrogation light sources for photoacoustic computed tomography (PACT). Permanent ORW tuning is achieved by material deposition onto or subtraction from the top diaphragm of each element with sub-nanometer resolution. For demonstration, a SMOUT array is first fabricated, and its ORW is tuned for readout with an 808 nm laser diode (LD). Experiments are conducted to characterize the optical and acoustic performances of the elements within the center region of the SMOUT array. Two-dimensional and three-dimensional PACT (photoacoustic computed tomography) is also performed to evaluate the imaging performance of the ORW-tuned SMOUT array. The results show that the ORW tuning does not degrade the optical, acoustic, and overall imaging performances of the SMOUT elements. As a result, the fine-tuning method enables new SMOUT-based PACT systems that are low cost, compact, powerful, and even higher speed, with parallel readout capability.
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Integration of microlenses on surface-micromachined optical ultrasound transducer array to improve detection sensitivity for parallel data readout
This Letter reports the integration of microlenses (MLs) on a surface-micromachined optical ultrasound transducer (SMOUT) array to enable parallel ultrasound data readout from a multiplicity of elements. The MLs are fabricated by photoresist patterning and reflow, and their focal lengths are optimized with parametric studies. Experiments are conducted to characterize the acoustic responsivity and its uniformity of the SMOUT-ML elements under different conditions. The temporal stability of SMOUT-ML elements immersed in water is assessed by monitoring their acoustic response continuously for 1 week. Parallel ultrasound signal readout is simulated with a small group of SMOUT-ML elements. Experimental results show that high acoustic sensitivity and excellent long-term stability can be achieved by the ML-integrated SMOUT array, which could provide a promising approach for enabling parallel ultrasound data acquisition for improving the imaging speed of 3D acoustic tomography.
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- PAR ID:
- 10392826
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 48
- Issue:
- 3
- ISSN:
- 0146-9592; OPLEDP
- Format(s):
- Medium: X Size: Article No. 652
- Size(s):
- Article No. 652
- Sponsoring Org:
- National Science Foundation
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