Patent ID: 6782014
Filing Date: 2004-08-24
Classification: G02F

Abstract:
A method for converting a first light beam having a first frequency into a second light beam having a second frequency, the method comprising:providing an optical cavity that is defined by a cavity axis and first and second mirrors, spaced apart along the axis, and by first and second nonlinear crystals, spaced apart along the axis between the first and second mirrors, wherein each of the first mirror and the second mirror is substantially fully transmitting at each of frequencies &ohgr; and 3&ohgr; and is substantially fully reflecting at a frequency 2&ohgr;, where &ohgr; is a selected frequency; providing the first nonlinear crystal having a length d(1) and having a refractive index n(2&ohgr;;1) for incident light having said frequency 2&ohgr;; providing the second nonlinear crystal having a length d(2) and having a refractive index n(2&ohgr;;2) for incident light having said frequency 2&ohgr;; and providing the optical cavity with a selected length D that satisfies the relation {D+d(1)Â·(n(2&ohgr;;1)âˆ’1)+d(2)Â·(n(2&ohgr;;2)âˆ’1)}Â·(2&ohgr;/c)=N2Â·&pgr;, where N2 is a selected positive integer,providing a laser pump beam having pump photons with associated frequency 3&ohgr; within the cavity; allowing at least one pump photon to pass through and interact with a first crystal, positioned within the cavity, and to undergo a conversion to a first-converted photon and a second-converted photon, having substantially the respective frequencies 2&ohgr; and &ohgr;; allowing the first-converted photon to pass through and interact with a second crystal, positioned within the cavity, and to undergo a conversion to a third-converted photon and a fourth-converted photon, each having a frequency substantially equal to &ohgr;; and allowing the second-converted photon to pass through the second crystal, whereby the pump photon is converted to three photons, each with a frequency substantially equal to &ohgr;, each of which exits from the cavity through at least one of the first mirror and the second mirror.