Fluorescence measurements

Fluorescence measurements are required in many biology (chlorophyll and carotenoid), biomedical (fluorescence diagnosis of malignancies) and environmental applications.

Fluorescence measurements typically need a high sensitivity setup (AvaSpec-2048TEC recommended for integration times > 5 seconds). For most fluorescence applications the amount of fluorescence energy emitted is only 3% of the amount of excitation light energy. The fluorescence light is of a lower energy (higher wavelength) than the excitation energy and is usually scattered light (emits energy in all directions).

Most important consideration for the setup is to prevent excitation light to enter the spectrometer.

This can be done with different methods, where one does not exclude the other:

1.      Use an AvaLight-LED light source for excitation (small bandwidth), emitting no energy at fluorescence wavelength.

2.      Use an (interference) band pass or low pass filter in combination with an AvaLight-HAL light source for high output,
   small bandwidth excitation

3.      Make sure that the optical path for excitation light and fluorescence are 90 degrees perpendicular. This way the
   excitation light will not enter the receiving fiber (use of the CUV-UV/VIS-FL or the CUV-DHc/XE/LED)

4.      Use the fluorescence decay time to separate excitation energy from the integration time start pulse. For this a pulsed
   light source is required (pulsed laser or AvaLight-XE Xenon flash)

A typical setup for fluorescence measurements is given below: