Compact Background-Free Balanced Cross-Correlators
First Claim
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1. A method for precise detection of the timing error between laser pulses, the method comprising:
- directing first and second input pulses through a nonlinear medium and a group dispersion/delay element, generating a first-pass sum-frequency component from the first and second input pulses and changing the relative positions of the first and second input pulses;
directing the first-pass sum-frequency component and the first and second input pulses to an inline dichroic mirror that passes the sum-frequency component and reflects the first and second input pulses;
detecting the energy of the sum-frequency component that passed through the inline dichroic mirror;
directing the reflected first and second input pulses back through the group dispersion/delay element and nonlinear medium, changing the relative positions of the first and second input pulses and generating a second-pass sum-frequency component from the reflected first and second input pulses;
detecting the energy of the second-pass sum-frequency component; and
comparing the energy of the first-pass sum-frequency component with the energy of the second-pass sum-frequency component to determine the relative positions of the first and second input pulses.
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Abstract
A compact, background-free, balanced cross-correlator enables (a) the detection of a timing error between two ultrashort pulses with (sub-)femtosecond resolution and (b) the timing synchronization of ultrashort pulse lasers using the output signal of the detector to close a phase-locked loop and can therefore serve as an integral part of femtosecond timing distribution and synchronization systems.
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Citations
36 Claims
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1. A method for precise detection of the timing error between laser pulses, the method comprising:
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directing first and second input pulses through a nonlinear medium and a group dispersion/delay element, generating a first-pass sum-frequency component from the first and second input pulses and changing the relative positions of the first and second input pulses; directing the first-pass sum-frequency component and the first and second input pulses to an inline dichroic mirror that passes the sum-frequency component and reflects the first and second input pulses; detecting the energy of the sum-frequency component that passed through the inline dichroic mirror; directing the reflected first and second input pulses back through the group dispersion/delay element and nonlinear medium, changing the relative positions of the first and second input pulses and generating a second-pass sum-frequency component from the reflected first and second input pulses; detecting the energy of the second-pass sum-frequency component; and comparing the energy of the first-pass sum-frequency component with the energy of the second-pass sum-frequency component to determine the relative positions of the first and second input pulses. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27)
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28. An apparatus for precise detection of a timing error between laser pulses, the apparatus comprising:
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a first laser for generating a first input pulse; a second laser for generating a second input pulse; a first optical path extending from the first laser for transmitting the first input pulse; a second optical path extending from the second laser for transmitting the second input pulse and intersecting the first optical path; a balanced detector for detecting and comparing a pair of optical pulses; a joint optical path extending between the balanced detector and the intersection of the first and second optical paths; at least one material serving as a sum-frequency-generating nonlinear medium and as a group dispersion/delay element positioned in the joint optical path; an inline dichroic mirror designed to transmit to the balanced detector a first-pass sum-frequency component generated by the nonlinear medium from the first and second input pulses on a first pass traveling away from the lasers, wherein the inline dichroic mirror is further designed to reflect the first and second input pulses along the joint optical path back toward the lasers; an off-axis dichroic mirror positioned in the joint optical path between the nonlinear medium and the intersection of the first and second optical paths and designed and oriented to reflect a second-pass sum-frequency component generated by the nonlinear medium from the first and second input pulses on a second pass traveling back toward the lasers, while transmitting the first and second input pulses along the joint optical path, wherein the off-axis dichroic mirror is oriented to reflect the second-pass sum-frequency component out of the joint optical path; and an extension optical path extending from the off-axis dichroic mirror and positioned to transmit the second-pass sum-frequency component from the off-axis dichroic mirror to the balanced detector. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35, 36)
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Specification