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. Ultra-Narrow-Band Notch Filters reflect light with bandwidth as narrow as 5 cm^-1 while all other wavelength pass unaffected with total transmission as good as 95%. BNFs enable measurements of Stokes and Anti-Stokes Raman bands down to 5 cm^-1 with a single stage spectrometer. The filters can withhold cw light powers exceeding 1 kW/cm², temperatures up to 400°C, and are fully environmentally stable. The central wavelengths can be controlled with accuracy better than 0.1 nm and can be angle tuned as much as 100 nm.

BragGrate™ Notch Filter

Specifications

• Attenuation: 90-99.99% (OD1-4)
• Spectral bandwidth: <10 cm^-1
• Operating range: 400-2500 nm
• BNF Thickness: 2-4 mm
• Apertures: up to 25×25 mm²
• Angular selectivity: 1-70 mrad
• Incident/Diffracted Angles: 0-45 deg
• Transmittance: up to 95%
• Transmission ripple: <1% at ±0.5 nm from laser line (@633 nm)

Transmission spectrum of OD3@488 nm BragGrate™ Notch Filter with 12×12 mm2 clear aperture.

Standard Parameters

• Center Wavelength: 488, 514.5, 532, 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: ~2.5 mm

Advantages & Features

• Ultra-narrow rejection bandwidth
  
• Measurements of both Stokes and anti-Stokes modes
  
• No degradation in high power light
• Environmentally stable: high temperature operation, no humidity effects
  
• No polarization dependence

Raman spectra of l-cystine measured with a single-stage spectrometer and BragGrate™ Notch Filters at 3 different wavelengths. (Courtesy of HORIBA Jobin Yvon)

Applications

Ultra-low frequency Raman spectroscopy.