Abstract: A tunable filter device (2) comprising a waveguide containing a Bragg grating (4), and a planar substrate (6), the planar substrate (6) comprising a core (8), a first cladding (10) on a first side (12) of the core (8), and a second cladding (14) on a second side (16) of the core (8), the waveguide containing the Bragg grating (4) being positioned in the core (8), the planar substrate (6) being such that a part of the first cladding (10) is replaced with a liquid crystal (18), and the tunable filter device (2) being characterized in that the waveguide containing the Bragg grating (4) is ultraviolet light written, the first cladding (10) has a surface which is smooth, flat and uniform due to the waveguide containing the Bragg grating (10) being ultraviolet light written, and the liquid crystal (18) is in contact with the smooth, flat and uniform surface of the first cladding (10) whereby director orientation of the liquid crystal (18) is uniform, controlled and controllable.