Rotationally tunable optical delay line
First Claim
1. A tunable optical rotational delay line apparatus for providing a continually adjustable time delay between two orthogonally polarized co-linear laser pulses, the rotational delay line apparatus comprising:
- a. a rotational delay crystal made of a parallel flat birefringent crystal having an ordinary refractiveindex no and extra-ordinary refractive index ne, whereinthe unique optic axis of said rotational delay crystal is oriented at an angle β
to the rotational delay crystal surface normal, where β
is greater than 0 degrees and less than 90 degrees;
b. a means of rotating said rotational delay crystal about its surface normal;
c. whereby a time delay between said two orthogonally polarized co-linear laser pulses that travel through said rotational delay crystal can be continually adjusted byi. inclining said surface normal of said rotational delay crystal at an angle θ
to the direction of travel of said co-linear laser pulses, where θ
=no sin(β
);
ii. rotating said rotational delay crystal about its surface normal.
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Abstract
A rotationally tunable time delay line device for providing a continually adjustable time delay between two orthogonally polarized laser pulses is described. The device is comprised of one or more rotational delay crystals, each made of a flat uniaxially birefringent crystal with a special orientation of its internal optical axis. The time delay generated between the two orthogonally polarized laser pulses that travel through the rotationally tunable delay line can be continually adjusted by rotating the constituent rotational delay crystals around their surface normals. An application is demonstrated in detail where the rotationally tunable time delay line device is used to form an optical autocorrelator for measuring femtosecond or picosecond duration laser pulses.
14 Citations
13 Claims
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1. A tunable optical rotational delay line apparatus for providing a continually adjustable time delay between two orthogonally polarized co-linear laser pulses, the rotational delay line apparatus comprising:
-
a. a rotational delay crystal made of a parallel flat birefringent crystal having an ordinary refractiveindex no and extra-ordinary refractive index ne, wherein the unique optic axis of said rotational delay crystal is oriented at an angle β
to the rotational delay crystal surface normal, where β
is greater than 0 degrees and less than 90 degrees;b. a means of rotating said rotational delay crystal about its surface normal; c. whereby a time delay between said two orthogonally polarized co-linear laser pulses that travel through said rotational delay crystal can be continually adjusted by i. inclining said surface normal of said rotational delay crystal at an angle θ
to the direction of travel of said co-linear laser pulses, where θ
=no sin(β
);ii. rotating said rotational delay crystal about its surface normal. - View Dependent Claims (2, 3, 4)
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5. An autocorrelator for measuring a laser pulse comprising:
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a. a circular polarizer; b. a rotational delay crystal made of a parallel flat birefringent crystal having an ordinary refractive index no and extra-ordinary refractive index ne, wherein the unique optic axis of said rotational delay crystal is oriented at an angle β
to the rotational delay crystal surface normal, where β
is between 0 and 90 degrees;c. a means of rotating said rotational delay crystal; d. a focusing lens; and
ae. photodetector unit f. wherein said circular polarizer changes an incident light ray into two orthogonally polarized collinear rays; g. whereby a time delay between said two orthogonally polarized co-linear laser pulses that travel through said rotational delay crystal can be continually adjusted by i. inclining said surface normal of said rotational delay crystal at an angle θ
to the direction of travel of said co-linear laser pulses, where θ
=no sin(β
);ii. rotating said rotational delay crystal about its surface normal; iii. whereby said focusing lens focuses said two orthogonally polarized laser pulses onto said photodetector unit and said photodetector unit generates an electrical current proportional to said time delay generated by said rotational delay crystal. - View Dependent Claims (6, 7, 8, 9, 10)
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11. A method of generating a time delay between two orthogonally polarized light pulses comprising
a. inclining the surface normal of a flat birefringent crystal at an angle θ - to the direction of travel of the incident light pulses said birefringent crystal having an internal unique optic axis oriented relative to said surface normal of said birefringent crystal at an angle of β
=arcsin(θ
)/no where θ
is such that β
is greater than 0 degrees and less than 90 degrees;b. providing a means of rotating said birefringent crystal, whereby a time delay between said two orthogonally polarized laser pulses that travel through said rotational delay crystal can be continually adjusted by rotating said rotational delay crystal about its surface normal. - View Dependent Claims (12, 13)
- to the direction of travel of the incident light pulses said birefringent crystal having an internal unique optic axis oriented relative to said surface normal of said birefringent crystal at an angle of β
Specification