Broadband cavity enhanced UV-VIS absorption spectroscopy for picolitre liquid samples

Area of Science:

• Analytical Chemistry
• Spectroscopy
• Optical Engineering

Background:

• Absorption spectroscopy is vital for label-free analysis but limited by short pathlengths in small liquid samples.
• Enhancing sensitivity is crucial for analyzing micro-volume liquid samples effectively.

Purpose of the Study:

• To develop an ultrasensitive broadband absorption spectrometer for thin liquid films.
• To improve sensitivity in absorbance measurements using an optical cavity.

Main Methods:

• Implemented a fiber-based absorption spectrometer with an optical cavity (CEASpec).
• Utilized dielectric mirrors to define a 200 nm bandwidth (250-450 nm).
• Employed 400 μm optical fibers for a sensing volume of 630 picoliters (5 μm film thickness).

Main Results:

• Achieved cavity enhancement factors of approximately 200× across a broad wavelength range.
• Demonstrated the instrument's capability using Amphotericin B as a test analyte.
• Successfully increased sensitivity for thin liquid film analysis.

Conclusions:

• The developed CEASpec offers a significant advancement for ultrasensitive absorption spectroscopy of small liquid volumes.
• This technique overcomes sensitivity limitations inherent in classical absorption spectroscopy for micro-scale samples.
• The CEASpec provides a powerful tool for various analytical applications requiring high sensitivity and small sample volumes.