Tunable time plate
AssigneeUniwave Technology, Inc.
InventorChaozhi Wan
Life of this patent
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Abstract
A tunable time plate device for providing a continually adjustable time delay between two linearly polarized laser pulses .omega..sub.1 and .omega..sub.2. The device comprises a time plate made of a parallel flat birefringence crystal having a principal axis of refractive index n.sub.z parallel to its surface, and a principal axis of refractive index n.sub.x having an angle .phi. to its surface normal. The time plate is rotatably mounted such that it is rotatable about its n.sub.z principal axis for tuning a time delay between the two laser pulses as they travel through the time plate which is a function of an incident angle .theta. between its surface normal and the propagation direction of the laser pulses. The time delay therefore can be continually adjusted by rotating said time plate to change said incident angle .theta..
Claims20
An apparatus for providing a continually adjustable time delay between two laser pulses .omega..sub.1 and .omega..sub.2 which are linearly polarized respectively along the Z-axis and the X-axis, and propagate in a direction along the Y-axis, of a Cartesian coordinate system, the apparatus comprising:
- a. a time plate made of a parallel flat birefringence crystal having a principal axis of refractive index n.sub.z parallel to its surface, a principal axis of refractive index n.sub.y, and a principal axis of refractive index n.sub.x having an angle .theta. to its surface normal, where n.sub.x is different from n.sub.y and n.sub.z ;
- b. said time plate rotatably mounted such that its n.sub.z principal axis coincides with said Z-axis, and it is rotatable about its n.sub.z principal axis for adjusting a time delay between said two laser pulses .omega..sub.1 and .omega..sub.2 as they travel through said time plate, which time delay is a function of an incident angle .theta. between said surface normal of said crystal and said propagation direction of said two laser pulses .omega..sub.1 and .omega..sub.2 ;
- c. whereby said time delay can be continually adjusted by rotating said time plate to change said incident angle .theta..
A femtosecond third harmonic generator for generating a third harmonic generation pulse (3.omega.) from a fundamental pulse (.omega.) which is linearly polarized along the Z-axis and propagates in a direction along the Y-axis of a Cartesian coordinate system, the femtosecond third harmonic generator comprising:
- a. a second harmonic generation (SHG) crystal for generating a SHG pulse (2.omega.) which is linearly polarized along the X-axis of said Cartesian coordinate system;
- b. a half-waveplate positioned behind said SHG crystal for rotating said fundamental pulse (.omega.) to polarize along said X-axis;
- c. a third harmonic generation (THG) crystal positioned behind said half-waveplate for generating said THG pulse (3.omega.) from said fundamental pulse (.omega.) and said SHG pulse (2.omega.);
- and
- d. a time plate made of a parallel flat birefringence crystal having a principal axis of refractive index n, parallel to its surface, and a principal axis of refractive index n.sub.x having an angle .phi. to its surface normal, and rotatably mounted between said SHG crystal and said half-waveplate, such that its n.sub.z principal axis coincides with said Z-axis, and it is rotatable about its n.sub.z principal axis, for adjustably compensating a time delay between said fundamental pulse (.omega.) and said SHG (2.omega.) after they travel through said SHG crystal, where the amount of time delay compensation is a function of an incident angle .theta. between said surface normal of said time plate crystal and said propagation direction of said fundamental pulse (.omega.) and said SHG pulse (2.omega.);
- e. whereby said time delay compensation can be continually adjusted by rotating said time plate crystal to change said incident angle .theta..
An autocorrelator for measuring a laser pulse having two polarization components .omega..sub.z and .omega..sub.x which are linearly polarized respectively along the Z-axis and the X-axis of a Cartesian coordinate system, the autocorrelator comprising:
- a. a time delay unit further comprising at least one time plate made of a parallel flat birefringence crystal having a principal axis of refractive index n.sub.z parallel to its surface, and a principal axis of refractive index n.sub.x having an angle .phi. to its surface normal, and rotatably mounted such that its n.sub.z principal axis coincides with said Z-axis, and it is rotatable about its n.sub.z principal axis, for adjusting a time delay between said two polarization components .omega..sub.z and .omega..sub.x after they travel through the at least one time plate crystal, where the time delay is a function of an incident angle .theta. between said surface normal of said time plate crystal and the direction propagation of said two polarization components .omega..sub.z and .omega..sub.x ;
- and
- b. an autocorrelation unit further comprising at least one second harmonic generation (SHG) crystal for autocorrelation;
- c. whereby a SHG signal (2.omega.) can be generated for detection when said two polarization components .omega..sub.z and .omega..sub.x overlap each other in time which is controlled by said time delay, which is in turn generated and adjusted by said time delay unit.
Dependencies are inferred from the claim text.