Nested-cavity optical parametric oscillator for fast frequency tuning

A doubly resonant optical parametric oscillator with achromatic phase-maintaining pump reflection comprising:

• a pump radiation source at a frequency fp, and comprising in the forward propagation direction of the pump radiation:
• a non linear crystal having a front face and a rear face,
• an achromatic mirror situated downstream of the rear face of the crystal, defining with a first mirror situated on the front face of the crystal,
• a first resonant cavity for the radiation signal at the frequency fs and with a second mirror situated upstream of the front face of the crystal,
• a second resonant cavity for the complementary radiation at the frequency fc, the two cavities, of respective optical lengths ls and lc, forming a doubly resonant resonator for a single pair of longitudinal signal and complementary modes, the pump radiation at the frequency fp makes through the crystal a forward path entering via the front face of the crystal and exiting via the rear face of the crystal, then, after reflection on the achromatic mirror,
• a backward path entering via the rear face of the crystal, the optical indices of which are respectively ns and nc at the signal fs and complementary fc frequencies, the crystal is wedged with its rear face inclined along a non zero angle α with respect to the direction x orthogonal to the direction z of propagation of the radiations, the crystal being moveable in the plane xz,
• wherein the crystal is moveable in translation in the plane xz along a direction inclined by a non zero angle b with respect to the direction x such that
• tg
• ⁢
• ⁢
• β
• =
• (
• n
• c
• -
• 1
• )
• +
• R
• ·
• (
• n
• s
• -
• 1
• )
• R
• ⁢
• tg
• ⁢
• ⁢
• α
• ,
• with
• R
• =
• (
• f
• s
• f
• c
• ⁢
• l
• c
• l
• s
• )
• ,
• to modify simultaneously the respective optical lengths ls and lc of the two resonant cavities in a ratio such that the double resonance for a single pair of longitudinal signal and complementary modes is maintained, and as a result the values of the frequencies fs and fc are continuously tunable over a wide range.