BragGrate™ Notch Filter

Ultra Narrow Bandstop Filter for Rayleigh light suppression

BragGrate™ Notch Filter (BNF) is a reflective volume Bragg grating recorded in a bulk of photosensitive silicate glass. BNF reflects light with bandwidth as narrow as 5 cm-1 while all other wavelength pass unaffected with total transmission as good as 95%.BNFs enable Raman shift measurements of 5-10 cm-1 from the laser line. The filters are stable to light powers exceeding 10 kW, temperatures up to 450°C, and are fully environmentally stable. The central wavelengths can be controlled with accuracy 0.1-0.5 nm and can be angle tuned up to 10 nm.

BragGrate™ Notch Filter

Specifications

• Attenuation: 90-99.99% (OD1-4)
• Spectral bandwidth: 20 pm to 20 nm (<10 cm-1)
• Operating range: 350-2700 nm
• Grating Thickness: 1-10 mm
• Apertures: up to 35×35 mm
• Angular selectivity: 10-100 mrad
• Incident/Diffracted Angles: 0-30 deg
• Grating to surface tilt angle: 0-10 deg
• Transmission ripple: < 1-2% at ±0.5 nm from Rayleigh line (@633 nm)

Attenuation of 3-mm thick BragGrate™ Notch Filter with 12×12 mm2 clear aperture at 633 nm.

Standard Parameters

• Center Wavelength: 632.8, 785, 1064 nm
• Spectral Bandwidth (FWHM): <10 cm-1
• Attenuation: 90; 99%; 99.9% (OD1; OD2; OD3)
• Lateral Dimensions: 12.5×12.5 mm2
• Thickness: 1-4 mm

Advantages & Features

• Very narrow Rayleigh rejection bandwidth < 5 cm-1
  
• Allows measuring Raman Stokes and anti-Stokes modes
  
• Low wavefront distortion
• No degradation in high power light
• Environmentally stable: temperatures < 450°C; no humidity effects
  
• Wide wavelength range: 350-2500 nm
• No polarization dependence
• Low transmission ripple
• Monochromator linewidth in small-size notch filters

BNF transmission characteristics with 99.9% attenuation and 0.25 nm bandwidth

Applications

BragGrate Notch Filters are ideal for Raman spectroscopy applications and enable low wavenumber measurements down to 5-10 cm-1.