A laser device includes: an amplifying medium (1, 7) adapted to generate a fundamental wavelength laser beam (13); a birefringent non-linear medium (3, 20, 20) for doubling the fundamental wavelength laser beam to generate a harmonic wavelength laser beam (14); a polarizing medium (1b, 5, 6, 2, 8, 9, 16, 20) for selecting a fundamental wavelength laser beam polarization, the polarizing medium being such that the fundamental wave at its output remains parallel to the fundamental wave at its input. The invention is characterized in that the polarizing medium (1b, 5, 6, 2, 8, 9, 16, 20) has an output side (2b) perpendicular to the fundamental wave exiting the polarizing medium. The amplifying medium, the birefringent non-linear medium are mutually integral so as to constitute a monolithic resonant cavity.