Moiré apodized reflective volume Bragg grating

Volume Bragg grating (VBG) with refractive index modulation (RIM) apodized with sinusoidal semiperiod profile is studied theoretically and experimentally. An apodized VBG of this type was fabricated with a sequential recording of two VBGs with slightly different resonant Bragg wavelengths in the same glass wafer. As a result, a moire pattern was produced with a constant average refractive index and a slow sinusoidal envelope of RIM. Modeling showed that an apodized VBG with a sinusoidal semiperiod has provided a suppression of the sidelobes in the reflection spectrum. The experimental measurements are in good agreement with the theoretical predictions. This type of VBG is suitable for high-resolution spectroscopy applications due to a significant reduction of sidelobes.