Narrow-Line Notch Filter for Ultra Low-Frequency Raman Spectroscopy
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 bandwidths as narrow as 5 cm-1 while all other wavelengths pass unaffected with up to 95% total transmission. BNF’s enable simultaneous measurements of Stokes and Anti-Stokes Raman bands down to 5 cm-1 with a single-stage spectrometer. Our Notch filters can withhold temperatures of up to 400°C and are fully environmentally stable with a practically unlimited lifetime. Central wavelengths of the filters can be angle tuned by several nanometers without reduction of the filter optical density.
Specifications
- Achievable attenuation: > 99.99% (OD4+)
- Spectral bandwidth (FWHM): ~ 5 cm-1
- Operating range: 400-2500 nm
- BNF Thickness: 2-4 mm
- Apertures: up to 25×25 mm2
- Angular selectivity: 2-10 mrad
- Incident/Diffracted Angles: 0-45 deg
- Transmittance: up to 95%
- Transmission ripple: <1% at ±0.5 nm from laser line (@633 nm)
Standard Parameters
- Center Wavelength / Transmission: 488nm/75%; 514.5nm/78%; 532nm/80%; 632.8nm/88%;
785nm/90%; 1064nm/95% - 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
- Achievable in any custom wavelengths in the
range from 405 nm to 2 µm - Spectral Bandwidth (FWHM): 5-8 cm-1
- Attenuation: OD3, OD4
- Lateral Dimensions: 11×11 or 12.5×12.5 mm2
- Optional 1-inch round mount
- 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
Applications
Ultra low-frequency THz Raman spectroscopy
- Raman Imaging
- Thomson Scattering
Ultra-low frequency Raman spectrum of SiGe superlattice at 532 nm with LabRAM HR Evolution and BragGrate Notch Filters (Courtesy of P.H. Tan, Institute of Semiconductors, CAS, Beijing, P.R. China)
Transmission spectrum of OD3@488 nm BragGrate™ Notch Filter with 12×12 mm2 clear aperture.