Our Colored-Glass Alternative filters are constructed using optical thin-film coating technology. Using Newport's patented Stabilife® coating technology, many layers of refractory metal oxide film are deposited under vacuum in a precise sequence, defining the spectral signature of the filters. Unlike Colored-Glass filters which rely upon absorption to create the filter's spectral response, CGA filters utilize optical interference phenomena to create wide bands of very-high reflectance to create the blocking region of the filters, and wide bands of very-low reflectance to create the transmission bands of the filters.
Steep transitions from blocking to transmission
High transmission of >90% average (typical)
Excellent blocking of >5 OD
Patented Stabilife® coatings
Wavelength stability in any environment
Note: Specifications below are common to all products presented. See Individual product details for complete information. Cut-on/Cut-off Wavelength 300 - 1000 nm Abrasion, Adhesion, Hardness MIL-C-48497 Temperature Range -100 to 400 º C Thickness 1.1 mm (typical) Humidity Resistance MIL-STD-810, Method 507.3, Procedure III, Modified to 40 cycles
Angle of Incidence Effects
The cut-on wavelength of Newport Stabilife™ Colored-Glass Alternative filters will slightly shift lower in wavelength with an increase in the angle of incident collimated light. The amount of wavelength shift is dependent upon the incident angle and the effective index (ne) of the filter. This feature can be very useful in research applications by being able to custom tune a CGA filter to a specific desired wavelength. The following formula may be used to determine the wavelength shift of a filter in random polarized collimated light: λθ = λ0 (ne2 – sin2 θ)½ (ne)-1 where λθ = Cut-on wavelength at θ° angle of incidence λ0 = Cut-on wavelength at 0° angle of incidence θ = Angle of incident light off normal incidence ne = Effective index of refraction; specified as a numerical value derived from the indices of the thin film layers of the CGA filter
In some applications, the incident light is presented at the filter in a convergent or divergent cone. The cone is made up of many light rays at various angles ranging from normal incidence to the extreme angle defining the full cone. The effect of this collection of rays is a weighted average of incident light, producing a wavelength shift toward shorter wavelengths that is smaller than the shift that would be produced if collimated light was presented to the filter at the extreme angle of the full cone.
CGA filters have been evaluated for stain resistance using the Acid Resistance test set forth in ISO 8424. This test is used to determine the surface change that results from exposure to a strong acidic substance. The surface is exposed to a Nitric Acid solution (0.5M/l) having a pH of 0.3 ± 0.05. Testing is conducted to determine the amount of time needed to etch into the surface to a depth of 0.1 µm. Newport's CGA filters have been confirmed to meet an SR1 rating which corresponds to greater than 100 hours of exposure. Since CGA filters are constructed of very thin layers of vacuum-deposited thin-film coating, an etch depth of 0.1 µm would likely result in a significant change in the spectral performance of the filter. No spectral change was evident after testing indicating an absence of any significant etching after the 100 hour exposure.
Abrasion Resistance, Adhesion, & Humidity Resistance
CGA filters have been qualified for adhesion using the snap tape test specified in MIL-C-48497, for abrasion resistance using the eraser test specified in MIL-C-675, and for humidity resistance using the aggravated test specified in MIL-STD-810E. These tests are commonly used as benchmarks for determining the robustness of thin film coatings.
The extreme hardness of the Stabilife® coatings used to manufacture Colored-Glass Alternative Filters allows these filters to be subjected to normal and severe weather conditions as well as to the repeated handling and cleaning that is commonplace for filters that are used in a lab environment, without sustaining any surface degradation. Unlike some Colored-Glass Filters that can suffer surface damage from prolonged exposure to rain or submersion in water, CGA filters maintain their clarity and spectral performance under such extreme conditions.
Stabilife® coatings used to manufacture our CGA filters have been deployed in applications where they are exposed intense ultraviolet and high energy visible radiation with no change in spectral performance after prolonged exposure. These filters have also been evaluated for Laser Damage Threshold using a frequency-doubled Nd:YAG laser operating at 532 nm with a pulse width of 10 ns and a repetition rate of 20 Hz. Typical damage threshold values exceed 1.0 J/cm2 .
Restrictions on Hazardous Substances (RoHS)
Unlike several Yellow, Orange, and Red Colored-Glass filters, Newport's Colored-Glass Alternative filters are fully compliant with RoHS regulations. They do not rely on a exemption and therefore, are not subject to the uncertainty of the review process.
Colored-Glass Alternative filters are qualified for use at continuous operating temperatures between -100°C and +400°C.
Newport's Colored-Glass Alternative filters were originally developed for custom and OEM applications either as alternatives to a Colored-Glass filter that utilized non-RoHS compliant material in it formulation, as replacements of a Colored-Glass filter that had been discontinued by one of the major Colored-Glass filter manufacturers, or as a new product to fill a gap in the wavelength offering of the major Colored-Glass filter manufacturers. The versatility of our coating processes and equipment support our ability to offer unlimited combinations of wavelength, size, shape, thickness, optical figure, surface quality, etc.. In the table that follows, we have listed some of the principle capability specifications for CGA filters Please provide your detailed requirements to our technical sales team and allow us to engineer the exact solution to meet your application.