Active optical resonator for frequency conversion

A method for generating coherent signal light in an optical cavity, comprising:

• providing said optical cavity with coherent pump light, said optical cavity being resonant for the signal light to be generated,
• converting said coherent pump light into coherent signal light through a parametric optical mixing process,
• amplifying said coherent signal light in a non-parametric optical amplification process to only partially compensate for passive optical roundtrip losses of said optical cavity, thereby obtaining lower effective roundtrip losses for the optical cavity,
• adjusting an intracavity optical power of said coherent pump light above a threshold value, where a parametric gain for the parametric optical mixing process is balancing said effective roundtrip losses in a spectral region occupied by the signal light, thereby inducing sustained oscillations of the signal light in the optical cavity,
• wherein a non-parametric gain for said non-parametric optical amplification process is limited to be less than the passive optical roundtrip losses over a gain bandwidth associated with the parametric optical mixing process.

A method for building an optical parametric oscillator, the method comprising:

• providing an existing optical cavity and an optical power regulator for adjusting an intracavity optical power of coherent pump light injectable into the existing optical cavity,
• wherein the existing optical cavity includes a parametric gain element for converting coherent pump light into coherent signal light through an instantaneous nonlinear optical interaction, a parametric gain of the parametric gain element depending on said intracavity optical power of said coherent pump light, where sustained oscillations of the coherent signal light are induced in the optical cavity above a threshold value of said intracavity optical power,
• obtaining the passive optical roundtrip losses of said existing optical cavity in a spectral region corresponding to a gain bandwidth of the parametric gain element, and
• upgrading the existing optical cavity by:
• inserting a non-parametric gain element for amplifying said coherent signal light and configuring the non-parametric gain element to have a non-parametric gain less than the obtained passive optical roundtrip losses in said spectral region if the existing cavity is without a non-parametric gain element, or else if the existing cavity comprises a non-parametric gain element for amplifying said coherent signal light gain, modifying that non-parametric gain element to have a non-parametric gain less than the obtained passive optical roundtrip losses in said spectral region, or inserting an additional optical attenuator to modify the obtained passive optical roundtrip losses in said spectral region such that a non-parametric gain of that non-parametric gain element is less than the modified passive optical roundtrip losses in said spectral region, and
• adjusting a length of the existing optical cavity to make it resonant for the converted coherent signal light.