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ALPHA Technology

Alpha Technology is the culmination of Omega’s ongoing research and development regarding filter design and deposition techniques.  Employing a proprietary method of controlling the coating process, this technology yields filters with exceptionally high signal-to-noise, as well as, steep transition slopes suitable for the most demanding applications.  With Alpha Technology, optical systems achieve the highest level of spectral discrimination – images are brighter, contrast is enhanced and instruments perform to the limits of detection.  Whenever an optical design demands the utmost level of precision, Alpha Technology is the obvious choice. 


Features/Benefits/Critical Specifications:

  • Extremely sharp transitions from stopband to passband
  • Precise, repeatable location of cut-on/cut-off wavelengths, tolerances
    within +/-0.01 to +/-0.005 of the edge 0.3OD - wavelength (50%)
  • Transmission 85% avg., 80% minimum, up to 8% gain with anti-reflection coatings
  • Tightly controlled ripple at cut-on
  • Nearly uniform transmittance across the passband
  • Exceptional attenuation of out-of-band signal
  • Single surface coatings suitable for PMT and silicon detectors
  • Optical quality transmitted wavefront
  • Longpass, shortpass and bandpass spectral profiles

 

5-Decade Slope Factor:
Slope factor is a measure by which the sharpness of transition between attenuation and transmission is achieved.  The industry standard is a 1-Decade slope factor measured between 80% and 10% transmission. Omega’s Alpha Technology raises the bar by using a 5-Decade slope factor defined as:

                   

Where (wavelength sign) OD5 is the wavelength at which an optical density of 5 is achieved (.001% transmission).  Note that optical density of 0.3 is equivalent to 50% transmission.

Typical industry longpass filters display a 5% 1-Decade slope factor.  Alpha Technology produces slope factors 5-50 times steeper and controls these edges to the following values at a 5-Decade slope factor: 1% Epsilon, 3% Gamma, and 5% Beta (see figure).

                   

Alpha Epsilon – 1% 5-Decade Slope Factor
A superior filter for Raman and other demanding applications requiring superior spectral discrimination.  These filters match the performance of a holographic Super Notch in edge steepness and depth of blocking.


Alpha Gamma – 3% 5-Decade Slope Factor
Steep edges, broader transmission and blocking regions with the same edge precision and smooth passband provided by the Alpha Epsilon design.  Ideal for most fluorescent applications.


Alpha Beta – 5% 5-Decade Slope Factor
For less demanding applications and a better value than catalog filters.  Much sharper edge precision than competitive long/shortpass filters.


Free Spectral Range and Blocking:
Longpass filters have a stopband from deep UV to cut-on edge and a passband from cut-on edge to 2500nm.  Blocking performance is measurable to >/=OD5 minimum and >/=OD20 (in theory) for Alpha Epsilon.


Shortpass filters have a stopband from cut-off edge to the limits of a PMT or CCD detector sensitivity and a transmission band from cut-off to 1.3 x cut-off or 400nm.