A frequency tuneable laser device comprising a laser cavity formed from a plurality of optical components, the plurality of optical components comprising a laser source for generating a beam of light, a spectral tuning element and one or more further optical components (142, 144, 146, 152) for directing the beam of light on to the spectral tuning element, wherein at least one of the plurality of optical components (144, 146) is moveable in a first degree of freedom and such movement of said at least one moveable optical component (144, 146) in the first degree of freedom simultaneously alters the effective optical path length of the laser cavity and the tuning frequency of the spectral tuning element thereby providing frequency tuning in which mode hopping is suppressed, wherein the effective optical path length and the tuning frequency are substantially insensitive to any movement of said at least one moveable optical component (144, 146) in degrees of freedom other than the first degree of freedom, and characterised in that: the at least one optical component (144, 146) moveable in the first degree of freedom comprises a first mirror and a second mirror carried by a moveable member, the first and second mirrors (144, 146) having a fixed position relative to one another and having inwardly facing reflective surfaces that are substantially parallel, the spectral tuning element comprises a stationary etalon arranged in the optical path between the first and second mirrors (144, 146), wherein the etalon is anchored in position and is not attached to, and does not move with, the moveable member, in use, light from the laser source is reflected from the first mirror to the second mirror via the etalon, with the light then being directed to, and reflected from, a fixed position mirror and returning to the laser source along the same optical path thus forming a resonant cavity, movement of the at least one moveable optical component (144, 146) in the first degree of freedom comprises rotation of the moveable member, and hence the first and second mirrors (144, 146), about a rotation axis that is substantially parallel to the reflective surfaces of the mirrors (144, 146) and substantially perpendicular to the optical path between the mirrors (144, 146), and rotation of the moveable member about the rotation axis alters the angle that light passes through the etalon and hence simultaneously alters the tuning frequency of the etalon and the effective optical path length of the laser cavity. the at least one optical component (144, 146) moveable in the first degree of freedom comprises a first mirror and a second mirror carried by a moveable member, the first and second mirrors (144, 146) having a fixed position relative to one another and having inwardly facing reflective surfaces that are substantially parallel, the spectral tuning element comprises a stationary etalon arranged in the optical path between the first and second mirrors (144, 146), wherein the etalon is anchored in position and is not attached to, and does not move with, the moveable member, in use, light from the laser source is reflected from the first mirror to the second mirror via the etalon, with the light then being directed to, and reflected from, a fixed position mirror and returning to the laser source along the same optical path thus forming a resonant cavity, movement of the at least one moveable optical component (144, 146) in the first degree of freedom comprises rotation of the moveable member, and hence the first and second mirrors (144, 146), about a rotation axis that is substantially parallel to the reflective surfaces of the mirrors (144, 146) and substantially perpendicular to the optical path between the mirrors (144, 146), and rotation of the moveable member about the rotation axis alters the angle that light passes through the etalon and hence simultaneously alters the tuning frequency of the etalon and the effective optical path length of the laser cavity.