An optical lasing device comprising: a gain medium arranged in a lasing cavity having an optical axis, the gain medium providing light amplification; a periodic grid generator filter arranged in the lasing cavity; a channel selector arranged in the lasing cavity and configured to select a lasing mode of the amplified light corresponding to a frequency channel defined by the periodic grid generator filter according to an optimization criterion, the optimization criterion comprising tuning the channel selector within a frequency channel range such that a single lasing mode arises at a frequency corresponding to one channel of the periodic grid generator filter; wherein the channel selector comprises a Guided Mode Resonance tunable mirror including a grating layer and at least one active layer having a tunable refractive index, characterized in that the Guided Mode Resonance tunable mirror is tunable between a first value and a second value higher than the first value, wherein the second value of the tunable refractive index is such that at least two different waveguide modes are generated in the at least one active layer corresponding to at least two different reflection peaks, a main peak of the at least two reflection peaks being generated at a specified channels range, a secondary peak of the at least two different reflection peaks being generated outside the specified channels range; and by a band-pass filter arranged in the lasing cavity and configured to suppress lasing modes which are outside of a pass-band of the band-pass filter, wherein the pass-band of the band-pass filter is configured to coincide with the specified channels range. a gain medium arranged in a lasing cavity having an optical axis, the gain medium providing light amplification; a periodic grid generator filter arranged in the lasing cavity; a channel selector arranged in the lasing cavity and configured to select a lasing mode of the amplified light corresponding to a frequency channel defined by the periodic grid generator filter according to an optimization criterion, the optimization criterion comprising tuning the channel selector within a frequency channel range such that a single lasing mode arises at a frequency corresponding to one channel of the periodic grid generator filter; wherein the channel selector comprises a Guided Mode Resonance tunable mirror including a grating layer and at least one active layer having a tunable refractive index, characterized in that the Guided Mode Resonance tunable mirror is tunable between a first value and a second value higher than the first value, wherein the second value of the tunable refractive index is such that at least two different waveguide modes are generated in the at least one active layer corresponding to at least two different reflection peaks, a main peak of the at least two reflection peaks being generated at a specified channels range, a secondary peak of the at least two different reflection peaks being generated outside the specified channels range; and by a band-pass filter arranged in the lasing cavity and configured to suppress lasing modes which are outside of a pass-band of the band-pass filter, wherein the pass-band of the band-pass filter is configured to coincide with the specified channels range.