Frequency stabilization method and apparatus for parametric amplifiers and oscillators

Claim 2

Frequency stabilized parametric apparatus comprising means forming a source of coherent pump radiation (p), means forming a first nonlinear element coupled to said source for receiving pump radiation and for developing gain at signal (s) and idler (i) radiations for which the following relations between the frequencies and k vectors of the pump, signal, and idler radiations hold, omega p omega i+ omega s and kp congruent ki+ks, said signal, idler, and pump radiations becoming the output of said first nonlinear element, means forming a second nonlinear element, said first and second nonlinear elements being constructed and arranged such that the effect of passage of the pump radiation through one in developing gain at signal and idler radiations normally is at least partially cancelled in the second element, and means disposed for receiving the output of the first nonlinear element and for selectively modifying the characteristics of a predetermined frequency band, S, within said signal radiations so that gain cancellation of said predetermIned band in said second element is prevented, a resonator coupled across said first and second nonlinear elements and operative at one of said idler or signal frequencies, whereby a peak in the gain of the combined elements is obtained for said predetermined frequency band.

Claim 3

Apparatus as in claim 1 in which said pump radiation and said signal radiation are in the visible region of the spectrum and in which said source comprises a laser.

Claim 4

Apparatus as in claim 1 wherein said means for modifying the characteristics of said signal radiation includes a gas capable of shifting the phase of said selected frequency band so that cancellation in said second nonlinear element does not take place.

Claim 5

Apparatus as in claim 1 wherein said means for modifying the characteristics of said signal radiation includes gas having an absorption line at said frequency band S.

Claim 6

In frequency stabilized parametric apparatus, means adapted to receive a beam of coherent pump radiation, means forming a first nonlinear element coupled to said beam for receiving the pump radiation and for developing gain at signal (s) and idler (i) radiations for which the following relations between the frequencies and k vectors of the pump, signal and idler radiations hold: omega p omega i+ omega s and kp ki ks, said signal, idler and pump radiations becoming the output of said first nonlinear element, means forming a second nonlinear element, said first and second nonlinear elements being constructed and arranged such that the effect of passage of the pump radiation through the first element in developing gain at signal and idler radiations normally is at least partially cancelled in the second element, and means disposed in the radiation path between said first and second nonlinear elements and adapted to selectively modify the characteristics of a predetermined frequency band (S) within said signal radiation so that cancellation of said predetermined band in said second element is prevented a resonator coupled across said nonlinear elements said resonator being operative at the frequency of either the idler or the signal radiation, whereby the overall gain of the combined nonlinear elements and modifying means attains a peak at said predetermined frequency (S).

Claim 7

In frequency stabilized parametric apparatus, means adapted to receive a beam of coherent pump radiation, means forming a first nonlinear element coupled to said beam for receiving the pump radiation and for developing gain at signal (s) and idler (i) radiations for which the following relations between the frequencies and k vectors of the pump, signal and idler radiations hold: omega p omega i+ omega s and kp ki ks, said signal, idler and pump radiations becoming the output of said first nonlinear element, means forming a second nonlinear element, said first and second nonlinear elements being constructed and arranged such that the effect of passage of the pump radiation through the first element in developing gain at signal and idler radiations normally is at least partially cancelled in the second element, and means disposed in the radiation path between said first and second nonlinear elements and adapted to selectively modify the characteristics of a predetermined frequency band (S) within said signal radiation so that cancellation of said predetermined band in said second element is prevented a resonator coupled across said nonlinear elements said resonator being operative at the frequency of either the idler or the signal radiation, whereby the overall gain of the combined nonlinear elements and modifying means attains a peak at said predetermined frequency (S).

Claim 10

A method as in claim 6 in which said step of modifying said signal radiations includes absorbing said radiations.

Claim 11

A method as in claim 6 in which said modifying step includes shifting the phase of said selected frequency band so that cancellation in said second nonlinear element does not take place.