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Fine tuning of narrow-bandwidth interference filters based on volume holographic gratings fixed in photorefractive LiNbO3 has been demonstrated. A filter with a peak wavelength at 518.45 nm, peak reflectivity 32.5% and bandwidth of 50 pm was used. Filter tuning has been achieved both by varying the filter temperature and by applying an electric field. By varying the filter temperature between 35 and 60 degrees C a temperature tuning coefficient of 5.1 pm K-1 was obtained. The effect is induced by the temperature-dependent change of refractive index and by the lattice thermal expansion. By applying a direct current electric field, an electrical tuning coefficient of 5.9 pm kV-1 has been measured too. In this case the tuning mechanisms are the electro-optic and piezoelectric effects. On the other hand, with an applied alternating current electric field, a beam intensity modulation from 90% to 20% has been demonstrated.

The possibility of multiplexing holograms in LiNbOs by means of an applied electric field is investigated experimentally. The effect of an applied electric field on the recording of holographic gratings as well as on the Bragg condition for previously stored ones is studied in the reflection geometry. The conclusion is that two image holograms can be addressed using an electric field. This multiplexing is shown experimentally.