Optical parametric generator based on a slant-stripe periodically poled nonlinear material with optimized lateral output coupling of a terahertz signal
An optical parametric device comprising a slant-stripe periodically poled nonlinear material that is operable to generate signal in response to interaction with a pump wave, the non-linear interaction being such that the pump and idler waves are collinear and the signal wave is non-collinear relative to the pump and idler waves, wherein the slant-stripe non-linear material is able to generate two idler waves and two signal waves, and the device is adapted to allow for the selection and output coupling of a required one of the two signal waves.
1. An optical parametric device comprising a slant-stripe periodically poled non-linear material that is operable to generate two pairs of signal and idler waves in response to non-linear interaction with a pump wave, the non-linear interaction being such that the pump and idler waves are collinear and the signal wave is non-collinear relative to the pump wave and idler waves in each of the pairs, wherein the device is adapted to:
select a required signal wave by ensuring the required signal wave and its associated idler wave have a lower oscillation threshold than the other signal and idler wave pair, and
output couple the required signal wave by ensuring the required signal wave is incident on a side face of the slant-stripe periodically poled nonlinear material at an angle that prevents internal reflection.
2. The optical parametric device as claimed in claim 1 arranged to ensure that the signal wave associated with a phase matching solution corresponding to a lower oscillation threshold meets a nonlinear crystal side face at less than a critical angle.
3. The optical parametric device as claimed in claim 1 comprising one or more optical elements to allow for the selection and the output coupling of a required one of the two signal waves.
4. The optical parametric device as claimed in claim 3 comprising one or more optical elements operable to change the relative magnitudes of intracavity losses associated with the two idler waves so that only generated idler-waves correspond to the required one of the two signal waves.
5. The optical parametric device as claimed in claim 4 wherein the one or more optical elements are operable to suppress or reduce oscillation on the lower oscillation threshold for one of the two idler waves by increasing losses relative to a higher threshold wave.
6. The optical parametric device as claimed in claim 4 wherein the one or more optical elements induce frequency dependent losses.
7. The optical parametric device as claimed in claim 4 wherein the one or more optical elements comprise one or more dispersive elements.
8. The optical parametric device as claimed in claim 4 wherein the one or more optical elements are located in an idler cavity.
9. The optical parametric device as claimed in claim 4 wherein the one or more optical elements are operable to change a relative magnitude of intracavity losses comprise an intracavity etalon.
10. The optical parametric device as claimed in claim 3 comprising one or more optical elements operable to change a relative magnitude of optical feedback associated with the two idler waves such that an only idler-wave generated corresponds to the required one of the two signal waves.
11. The optical parametric device as claimed in claim 10 wherein the one or more optical elements operable to change the relative magnitudes of an optical feedback comprise a resonant reflector.
12. The optical parametric device as claimed in claim 1 that has a cavity for resonating the idler wave in each of the pairs or the pump wave.
13. The optical parametric device as claimed in claim 1 wherein the non-linear material is located within a cavity of the pump laser.