Frequency domain diffuse optical spectroscopy with a near-infrared tunable vertical cavity surface emitting laser

Area of Science:

• Biomedical Optics
• Laser Technology
• Spectroscopy

Background:

• Diffuse optical spectroscopy (DOS) is a valuable tool for non-invasive tissue analysis.
• Current systems can be bulky, limiting their application in wearable or portable devices.
• High spectral resolution is crucial for accurate material characterization.

Purpose of the Study:

• To present a novel approach for frequency domain diffuse optical spectroscopy (fd-DOS) using a tunable vertical cavity surface emitting laser (VCSEL).
• To demonstrate the feasibility of miniaturized, high spectral resolution optical sensing.
• To evaluate the performance of the VCSEL-based fd-DOS system for tissue optical property measurements.

Main Methods:

• Utilized an electrothermally tunable microelectromechanical systems (MEMS) topside mirror to achieve laser cavity resonance tuning.
• Employed a near-infrared tunable VCSEL (769-782nm) with single mode continuous wave (CW) output and 1.3mW peak power.
• Measured optical properties (absorption and reduced scattering) of a tissue-simulating phantom across the tunable laser range.

Main Results:

• The tunable VCSEL demonstrated suitability for fd-DOS applications.
• Optical properties were recovered with high accuracy: 0.0006mm⁻¹ for absorption and 0.09mm⁻¹ for reduced scattering.
• Performance was comparable to a broadband fd-DOS reference system.

Conclusions:

• Tunable VCSELs offer a promising solution for high spectral resolution optical sensing in a miniature format.
• This technology may enable the development of advanced wearable optical sensing devices.
• The presented approach advances the field of portable biomedical optics.