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The Ondax Narrow-band Notch Filters are based on volume holographic gratings (VHG's) manufactured in robust glass material . The filter is a single element composed of six bonded slanted reflective volume holographic gratings, each with optical density one, yielding a total rejection of OD 6.

Notch Filters are an essential component in Raman instruments. The purpose of the wavelength blocker is to greatly attenuate the backscattered light from the laser illuminating a sample under test, while letting the faint Raman spectrally shifted signature pass through. The Raman signal in the low frequency shift region (~10 cm-1), i.e. near the frequency of the excitation laser, contains critical information about molecular structure that, until now, has not been accessible unless using large and expensive instrumentation. The new Notch Filters are capable of observing these Raman signals near the excitation wavelength and are used in standard Raman instruments. These Notch Filters are compact (same size as a standard thin film/ holographic notch filters) realized by bonding individual notch filters without creating spurious multiple diffractions.

Power Handling: the glass material is resistant to average powers in excess of several kW/cm2 at 1064nm and peak power in excess of 170MW/cm2 peak power (fluence of 3.8 J/cm2) at 1064nm.

Ondax Notch Filters are available at wavelengths of 600nm to 1600nm. The filter is wavelength tunable via angle to match the wavelength of the light source. The standard 785nm Notch Filter is angularly tunable from 760nm to 785nm with an optical density of 6, 3dB bandwidth of 9cm-1 (0.55nm) and greater than 70% transmission.