Apparatus and method for providing a feedback measurement in a laser system
AssigneeNorthrop Grumman Corporation
InventorsRobert E. Ryan, Sal Soriano
Life of this patent
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Abstract
The feedback in a laser system is measured in near real time by inducing a frequency shift and the feedback being based on the phase shift undergone by the feedback beam in an external cavity. The frequency shift is induced by phase modulating the feedback beam, for example by varying the position of an optical element placed in the feedback beam upon applying a ramp signal to the optical element. Frequency is detected by a Fabry-Perot interferometer which generates an interference fringe pattern, the intensity of the central fringe being detected to determine the induced frequency shift in real time, the amount of feedback being proportional to the time of flight multiplied by the frequency shift.
Claims14
A device for providing a near real time optical feedback measurement in a laser system, said device comprising:
- means for phase modulating the feedback to induce a shift in a frequency of the feedback;
- frequency discriminating means for detecting in real time the frequency shift induced in said feedback;
- and
- means for computing an amount of feedback at a preselected location as a function of the detected frequency shift.
A method for providing a near real time feedback measurement in an optical system, said method comprising the steps of:
- (a) phase modulating said feedback at a preselected point within said optical system to induce a frequency shift in said feedback relative to an incident beam;
- (b) detecting said frequency shift in real time by passing the feedback through a frequency discriminator;
- and
- (c) calculating the amount of feedback at said point as a function of the detected frequency shift and roundtrip time of an external cavity.
Dependencies are inferred from the claim text.