Active tuning of temporal dispersion in an ultrashort pulse laser system
View Patent ↗A chirped pulse amplification (CPA) system and method is described wherein the dispersion of the system is tuned by actively tuning one or more system components, for example, using a temperature or strain gradient, or using actinic radiation. In other embodiments, an additional element, such as a modulator, is added to the CPA system to actively to tune the pulse. A pulse monitor is added to the system to measure an output pulse and provide feedback to one or more active tuning elements.
1. A chirped pulse amplification system, comprising:
a pulse generator, configured to generate a laser pulse;
a pulse stretcher, configured to generate a stretched pulse from the laser pulse by dispersing the laser pulse temporally as a function of wavelength;
a pulse amplifier, configured to generate an amplified pulse from the stretched pulse;
a pulse compressor, configured to generate a compressed pulse from the amplified pulse;
an active tuning element configured to tune a group velocity dispersion of the chirped pulse amplification system and control a temporal width of the compressed pulse; and
a pulse monitor configured to measure one or more characteristics of the compressed pulse, the active tuning element being responsive to an output of the pulse monitor.
2. The system of claim 1 , wherein the active tuning element compensates for dispersion variations caused by changes in an environment, alterations to an optical path length of free-space elements, or variations in pulse intensity.
3. The system of claim 1 , wherein the active tuning element compensates for dispersion variations in a Treacy compressor.
4. The system of claim 1 , wherein the active tuning element comprises a heating element or a physical beam coupled to the pulse stretcher or to the pulse compressor.
5. The system of claim 1 , wherein the active tuning element tunes the duration of the laser pulse.
6. The system of claim 1 , wherein the pulse monitor comprises a correlator or power meter configured to measure a temporal width of the compressed pulse.
7. The system of claim 1 , wherein the active tuning element comprises a modulator.
8. The system of claim 1 , wherein the active tuning element comprises a physical beam configured to apply a strain gradient to a fiber Bragg grating.
9. The system of claim 1 , wherein the active tuning element comprises a heater configured to apply a thermal gradient to a fiber Bragg grating.
10. The system of claim 1 , wherein the active tuning element comprises a Bragg fiber or a fiber Bragg grating constructed using photosensitive or photorefractive materials activated by actinic radiation.
11. The system of claim 1 , wherein tuning the group velocity dispersion includes applying a strain gradient, a heat gradient or actinic radiation to a Bragg fiber and results in a change to an optical band gap of the Bragg fiber.
12. The system of claim 1 , wherein a modulator chromatically disperses the laser pulse to generate a stretched pulse and actively tunes the chromatic dispersion to optimize an output pulse characteristic.
13. The system of claim 1 , wherein the active tuning element comprises part of a chirped pulse source.
14. The system of claim 1 , wherein the active tuning element is configured to tune at least dispersion and dispersion slope.