Optical system for providing short laser-pulses
The present invention deals with optical systems for providing short laser pulses. An object of the invention is to provide an optical system providing compact and cost-effective short laser-pulses using fibers with anomalous dispersion and high non-linear thresholds. The object is achieved by a short pulse optical system for generating or processing short laser-pulses, said optical system comprises an optical fiber in the form of a photonic crystal fiber arranged to provide guidance of light in the core region due to the photonic bandgap effect (PBG), where light propagates in a hollow or solid core surrounded by a Silica cladding comprising a substantially periodic distribution of micro-structural elements, and where the refractive index of the core is lower than the effective refractive index of the cladding. The invention may be useful in applications such as laser-based micromachining, thin-film formation, laser cleaning, in medicine and biology.
1. A short pulse optical system for generating short laser-pulses, said optical system being in the form of a modelocked laser, and comprising; an optical pump; and a laser cavity, comprising; an intracavity modulator; an intracavity dispersion compensating photonic bandgap (PBG) fiber, comprising a solid core that is substantially homogeneous and an all solid cladding, wherein the solid core has a refractive index that is lower than a refractive index of the cladding; a polarizing component adapted to provide the cavity with a single polarization; and an active medium optically coupled to said PBG fiber and said optical pump, wherein said PBG fiber is connected to said laser cavity via at least one splice; wherein any non-polarization maintaining fibers in the laser cavity are kept substantially straight.
2. A short pulse optical system according to claim 1 , wherein said optical pump is a laser diode.
3. A short pulse optical system according to claim 1 , wherein the intra cavity modulator is selected from the group consisting of an acousto-optic modulator, a LiNbO3 crystal, a semiconductor modulator, a saturable absorber, an APM, or coupled cavity modulators.
4. A short pulse optical system according to claim 1 , wherein the intra cavity modulator is a semiconductor saturable absorber mirror (SESAM) modulator.
5. A short pulse optical system according to claim 1 wherein the active medium is a waveguide or an actively doped semiconductor wafer.
6. A short pulse optical system according to claim 5 wherein the active medium is a doped fiber.
7. A short pulse optical system according to claim 6 wherein the active medium is a Large Mode Area actively doped photonic crystal fiber.
8. A short pulse optical system according to claim 7 wherein the laser cavity further comprises a semiconductor saturable absorber mirror (SESAM).
9. A short pulse optical system according to claim 1 , wherein the intracavity dispersion compensating PBG fiber and the active medium are coupled to each other with one or more intermediate light transmitting elements.
10. A short pulse optical system according to claim 7 , wherein the large mode area actively doped photonic crystal fiber is spliced to an index guiding and mode expanded fiber to provide a low loss combination of the two fibers.
11. A short pulse optical system according to claim 10 wherein the index guiding and mode expanded fiber is a standard fiber or a PCF.
12. A short pulse optical system according to claim 1 further comprising extra-cavity light transmission element(s) coupled to the laser cavity to receive an output beam therefrom.
13. A short pulse optical system according to claim 12 wherein the extra-cavity light transmission element(s) comprises one or more extra-cavity fibers.
14. A short pulse optical system according to claim 12 wherein the extra-cavity light transmission element(s) comprises elements for chirped pulse amplification, said elements comprising one or more elements for chromatically dispersing the optical pulses, one or more elements for amplifying the temporally broadened pulses, and one or more elements for recompressing.
15. A short pulse optical system according to claim 14 wherein the one or more extra-cavity elements for recompressing is a PBG fiber.
16. A short pulse optical system according to claim 15 wherein said PBG fiber for recompressing is a hollow core PBG fiber.
17. A short pulse optical system according to claim 14 wherein the extra-cavity element for amplifying the temporally broadened pulses is a Large Mode Area actively doped photonic crystal fiber.
18. A short pulse optical system according to claim 13 , wherein the extra-cavity comprises a PBG fiber.
19. A short pulse optical system according to claim 18 , wherein the PBG fiber of the extra-cavity is a hollow core PBG fiber.
20. A short pulse optical system according to claim 1 , wherein the intra cavity modulator is an active modulator.
21. A short pulse optical system according to claim 1 , wherein the intra cavity modulator is a passive modulator.
22. A short pulse optical system according to claim 8 , wherein said active medium has a high non-linear thresholds.
23. A short pulse optical system according to claim 14 , wherein said one or more elements for chromatically dispersing the optical pulses is selected from a pair of diffraction gratings, an optical fiber, or a fiber Bragg grating.
24. A short pulse optical system according to claim 6 , wherein the doped fiber is a Nd-, Yb—Er-, Pr- or a Tm-doped fiber.
25. A short pulse optical system according to claim 1 , wherein said solid core PBG fiber is coupled within the cavity via at least one splice to a fiber having a cladding without microstructures.
26. A short pulse optical system according to claim 12 , wherein the extra-cavity light transmission element(s) comprises elements for amplification and pulse compression.
27. A short pulse optical system according to claim 26 , wherein pulse compression is performed in a PBG fiber.
28. A short pulse optical system according to claim 1 , wherein said laser-pulses are in the range from 10 picoseconds (10*10 −12 s) to femtoseconds (10 15 s).