Theodore Maiman, the father of electro-optics, once dubbed laser technology as a solution looking for a problem. This came shortly after he had built the world’s first working laser using a ruby gain medium while others were researching gas lasing media. Within a few short decades, myriad additional laser technologies had come to the fore. Various problems had also arisen to fit these new solutions.
Lasers are now ubiquitous in science and technology. It has become relatively easy to generate coherent monochromatic laser beams that are either pulsed or continuous wave (CW). Various frequencies, intensities, pulse durations, wavelengths, and more are available to satisfy the different performance demands of applications from flow cytometry to Raman spectroscopy. But all of this relies on the proper implementation of specialized laser filters.
What is a Laser Filter?
Briefly: A laser filter is an optical device used to transmit desired wavelengths while attenuating out-of-band signals.
The goal is to optimize the signal-to-noise ratio by eliminating background signals like scattered light. Precision laser systems typically use an array of laser filters to optimize signals at both the source and the detector. Clean-up laser filters are usually deployed near the source to deliver maximum transmission of designated wavelengths. Rejection filters are used to prevent unwanted noise near the detector. This type of setup ensures the best possible signal integrity for laser-based spectroscopic tools.
But what are the best laser filters for each individual task?
Laser Line Filters
Engineered to transmit a narrow band centred on the resonance of the laser, line filters are essential in delivering that characteristic monochromatic beam. The best performance in laser clean-up is provided by ultra-narrow bandpass filters with sub-nanometre (nm) passbands for a custom wavelength.
At Omega Optical Filters, we provide high transmission ultra-narrow band line filters with extremely steep edges for a guaranteed single output wavelength. We offer Ultra NB filterswith custom wavelengths across the entire ultraviolet, visible, and near infrared (NIR) regions of the electromagnetic spectrum.
Designed to tackle the problem of scattered light by selectively transmitting short/long wavelengths, edge laser filters are important in signal-to-noise optimization. This is critical in spectroscopic applications where desirable signals can be significantly weaker than background noise. Edge laser filters are characterised as either long- or short-pass (LP/SP) barriers classified by their cut-on/off wavelength and the steepness of the edge, plus their reflection range. Choosing the right one will largely depend on the configuration of your system. We discuss a few examples and outline the importance of angle tuning on our laser filters application page.
Similar to edge filters, laser rejection filters are engineered to enhance signal acquisition by attenuating background noise. Also known as notch filters, rejection laser filters are used to selectively reject portions of the electromagnetic spectrum via attenuation and/or reflection. This specific frequency region is known as the stopband. The best rejection filters can block more than 99.9999% of light within a narrow range while offering broad transmission of other wavelengths.
Interested in deploying our laser filter solutions in your workflow? Simply contact a member of the Omega Optical team today and we will happily discuss design builds and filter specifications at your leisure.