Using Continuously Variable Filters for Fluorescence Spectroscopy

Fluorescence spectroscopy is the processes of analyzing the emissive, spectral characteristics of a fluorescent compound which has been excited by photons of light. Typically, a sample will fluoresce light with longer wavelengths thus lower energy than that which it absorbed, requiring sensitive equipment with a broad wavelength range and high optical blocking (OD) to accurately analyze its fluorescent properties. Specialized filters have been developed to analyze the wavelengths of fluorescence of a sample, including linear variable filters or continuously variable filters, which observe the spectral change of fluorescence continuously across a wide wavelength range.

This article will explore some of the properties and benefits of continuously variable filters from Delta Optical Thin Film, that are suitable for fluorescence spectroscopy:

Continuously Variable Filters for Fluorescence Spectroscopy

A typical fluorescent spectrometer consists of an energy source, an excitation wavelength selector, a sample holder, an emission wavelength selector, and a detector. The wavelength selector components are crucial in fluorescence spectroscopy as they are designed to continuously analyze photons of varying wavelengths, which fluoresce from a compound after excitation by a light source. The design and efficiency of wavelength selectors for fluorescence spectroscopy varies, but two of the primary options are monochromators and interference filters. Both offer the opportunity to continuously analyze fluorescence, but wedged interference filters have a greatly increased potential ‘light grasp’ than monochromators of similar bandwidth, with the potential to collect several thousand times their potential light quantity.

These continuously variable filters have a continuous relationship between the position on the filter and the observed wavelength, with wavelength tunings easily achieved by adjusting the filter placement. Delta Optical Thin Film produces a selection of robust filters for fluorescence spectroscopy with shift-free surface coatings and high laser damage thresholds, including:

  • Continuously Variable Long-Wave Pass filters (CVSLWP);
  • Continuously Variable Short-Wave Pass filters (CVSWP);
  • Continuously Variable Dichroics.

These Delta Optical Thin Film filters can be used separately to offer blocking which exceeds OD3 or combined to achieve blocking beyond OD5. With a continuous tuning of edge/center wavelengths across the full range, from 320 nm to 850 nm, and an average transmission exceeding 90%. These broader blocking ranges allow for reduced background noise to better distinguish between light emitting from the fluorescent compound and any background noise. These developments have radically extended the effectiveness and potential applications of continuously variable filters towards the advancement of fluorescence spectroscopy.

Delta Optical Thin Film’s interference filters have been implemented in the upcoming, innovative Dynamic VariChrome system from Edinburgh Biosciences. This motorized and programable module will allow users to achieve high transmission wavelength selection performances in smaller devices than has previously been possible, making the process more accurate, more affordable, and more efficient.


Fluorescence Spectroscopy with Delta Optical

Delta Optical Thin Film A/S has over fifty years’ experience designing and manufacturing components suitable for a range of optical monitoring applications, with a demonstrable track record of pushing the boundaries of accuracy, efficiency, and affordability in the manufacture of monochromators and interference filters.

If you require any more information about our continuously variable filters, or would like to hear about our impact in the expanding field of fluorescence spectroscopy, feel free to contact us.