Rapid optical tomographic vibrometry using a swept multi-gigahertz comb.

Area of Science:

• Optical physics
• Biomedical engineering
• Microelectromechanical systems (MEMS)

Background:

• High-frequency vibration analysis is crucial for understanding biological tissue dynamics and MEMS device performance.
• Existing methods often lack the speed and resolution required for detailed internal measurements.

Purpose of the Study:

• To introduce a rapid tomographic vibrometer technique for high-frequency internal vibration and transient measurements.
• To enable phase-sensitive tomographic measurements in the depth direction at multi-MHz scan rates.

Main Methods:

• Utilizing a frequency-modulated broadband electrooptic multi-GHz supercontinuum comb.
• Employing a unique frequency sweeping method via a dual-drive Mach-Zehnder modulator for direct amplitude and phase measurement.
• Implementing compressive sensing to reduce measurement points to vibration-localized depth regions.

Main Results:

• Demonstrated phase-sensitive tomographic measurement capability at multi-MHz scan rates.
• Achieved depth resolution of approximately 25 µm and precision of 1.0 nm in proof-of-principle experiments.
• Successfully performed tomographic transient displacement measurements on a glass film with a piezoelectric transducer.

Conclusions:

• The proposed rapid tomographic vibrometer technique offers high-frequency, high-resolution internal vibration measurement capabilities.
• This method is suitable for analyzing transient phenomena and tomographic distributions in biological tissues and MEMS devices.
• The technique's compressive sensing approach enhances measurement efficiency by focusing on relevant depth regions.