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BragGrate™- Bandpass Filter

Reflecting Bragg Grating (RBG) for spectral filtering

 

BragGrate™ Bandpass Filter is a reflecting Bragg grating (RBG) recorded in a bulk of photosensitive silicate glass. These filters are used to clean up laser spectral noise with a bandwidth as narrow as 50 pm in visible and near IR regions. In Raman spectroscopy applications, combining these Filters with matching BragGrate™ Notch Filters enables Raman shift measurements down to 5 cm-1 from the laser line. The widely used BragGrate™ filters have superior environmental stability and can handle high power optical radiation and high operations temperatures.

 

Bandpass fig 1

785 nm laser diode ASE background clean up with a BragGrate™ Bandpass filter
with bandwidth <7 cm-1

Specifications

  • Diffraction Efficiency (DE): >90%
  • Spectral Bandwidth: 50 pm to 0.5 nm
  • Operating Range λ: 350-2700 nm
  • Grating Thickness: 0.5-15 mm
  • Apertures: Up to 25 mm2
  • Deflection Angles: 5-90 deg

 

Standard Parameters

  • Center Wavelength: 405, 488, 514, 532, 633, 785, 1064 nm
  • Available Custom Wavelengths: 405 nm,
    442 nm, 458 nm, 473 nm, 477 nm, 491 nm,
    502 nm, 544 nm, 552 nm, 561 nm, 568 nm,
    588 nm, 594 nm, 612 nm, 647 nm, 660 nm,
    753 nm, 840 nm, 905 nm, 976 nm, 980 nm,
    1342 nm, 1352 nm, 1550 nm
    Bandpass fig 2

    Schematics of a possible RBG Bandpass filter configuration

  • Spectral Bandwidth (FWHM): <7 cm-1
  • Diffraction Efficiency: >90%
  • Lateral Dimensions: 5×5 mm2 and 11×11 mm2
  • Deflection Angle: 20 deg

 

Advantages & Features

  • High spectral selectivity
  • Superior environmental stability, no degradation over lifetime
  • High powered operations over 1 kW
  • High average power operation >20 W
  • High energy operations up to 5 J/cm2
  • No polarization dependence
  • Near-diffraction-limited beam quality
  • BragGrate Bandpass/Spatial Filter in a 12.5 mm round holder mounted in a kinematic mount for angle tuning and alignment

 

Applications

  • Ultra-low frequency (Terahertz) Raman spectroscopy
  • Spectral filtering and noise cleaning of laser beams
  • ASE filters for Raman laser diode sources
  • Spectral detection
  • Tunable filters for high resolution spectroscopy