Frequency-tripled fiber-MOPA
View Patent ↗In a frequency-tripled fiber-MOPA, a pre-amplified plane-polarized seed-pulse having a fundamental frequency is divided into two pulse-components, plane-polarized in polarization-orientations at 90-degrees to each other. The fundamental-wavelength pulse-components are amplified in a common amplifier-fiber. The amplified components are separately propagated on different optical paths. One of the amplified components is frequency-doubled. The frequency-doubled component on one path and fundamental-frequency component on the other path are then combined on a common-path and sum-frequency mixed to provide a frequency-tripled pulse.
1. A method for operating a pulsed MOPA including a polarization-maintaining fiber-amplifier having one or more fiber-amplifier stages, the method comprising:
generating a plane-polarized pulse to be amplified by the fiber-amplifier, the pulse having a fundamental frequency;
dividing the pulse into first and second plane-polarized pulse-components having polarization orientations at 90-degrees to each other;
amplifying the first and second plane-polarized pulse-components in the polarization-maintaining fiber-amplifier thereby providing first and second amplified plane-polarized pulse-components;
directing the first and second amplified plane-polarized pulse-components along respectively first and second separate optical paths; and
frequency-doubling the first amplified plane-polarized pulse-component in the first optical path, thereby generating a first frequency-doubled plane-polarized pulse-component having a frequency which is the second harmonic of the fundamental frequency.
2. The method of claim 1 , further including combining the first frequency-doubled pulse-component and the second amplified plane-polarized pulse-component along a common path, and generating a frequency-tripled plane-polarized optical pulse having a frequency three-times the fundamental frequency by sum-frequency mixing the first frequency-doubled plane-polarized pulse-component and the second amplified plane-polarized pulse-component.
3. The method of claim 2 , wherein the frequency-doubling of the first amplified plane-polarized pulse-component in the first optical path is type-1 frequency doubling.
4. The method of claim 3 , wherein the generation of the frequency-tripled plane-polarized optical pulse a frequency tripled plane-polarized optical pulse is by type-2 sum-frequency mixing the first frequency-doubled plane-polarized pulse-component and the second amplified plane-polarized pulse-component.
5. The method of claim 1 , further including frequency-doubling the second amplified plane-polarized pulse-component in the second optical path thereby generating a second frequency-doubled plane-polarized amplified pulse-component having a frequency which is the second harmonic of the fundamental frequency, combining the first and second frequency-doubled plane-polarized pulse-components along a common path, and generating a frequency-quadrupled plane-polarized optical pulse having a frequency four-times the fundamental frequency by frequency-doubling the first and second frequency-doubled pulse-components.
6. The method of claim 5 , wherein the frequency-doubling of the first and second amplified plane-polarized pulse-components in the first and second optical paths is type-1 frequency doubling.
7. The method of claim 6 , wherein the generating of the frequency-quadrupled plane-polarized optical pulse having a frequency four-times the fundamental frequency is by type-2 frequency-doubling the first and second frequency-doubled pulse-components.
8. The method of claim 1 , further including temporally separating the first and second plane-polarized pulse-components with respect to each other prior to the amplifying.
9. The method of claim 8 , wherein the temporal separation of the first and second plane-polarized pulse-components is by at least about 0.5 times the pulse duration thereof.
10. The method of claim 8 , further including temporally and spatially overlapping the temporally separated first frequency-doubled plane-polarized and second amplified plane-polarized pulse-components along a common path, and generating therefrom a frequency tripled plane-polarized optical pulse having a frequency three-times the fundamental frequency by sum-frequency mixing the first frequency-doubled plane-polarized pulse-component and the second amplified plane-polarized pulse-component.
11. A method for operating a pulsed MOPA including a polarization-maintaining fiber-amplifier having one or more fiber-amplifier stages, the method comprising:
generating a plane-polarized pulse to be amplified in the fiber-amplifier, the pulse having a fundamental frequency;
dividing the pulse into first and second plane-polarized pulse-components having polarization orientations at 90-degrees to each other;
temporally separating the first and second plane-polarized pulse-components with respect to each other;
amplifying the temporally separated first and second plane-polarized pulse-components in the polarization-maintaining fiber-amplifier thereby providing first and second temporally separated amplified plane-polarized pulse-components;
directing the first and second temporally separated amplified plane-polarized pulse-components along respectively first and second separate optical paths; and
frequency-doubling the first amplified plane-polarized pulse-component in the first optical path, thereby generating a first frequency-doubled plane-polarized amplified pulse-component having a frequency which is the second harmonic of the fundamental frequency.
12. The method of claim 11 further including temporally overlapping the first frequency-doubled plane-polarized pulse-component and the second amplified pulse-component along a common path, and generating a frequency-tripled plane-polarized optical pulse having a frequency three-times the fundamental frequency by sum-frequency mixing the first frequency-doubled plane-polarized pulse-component and the second amplified plane-polarized pulse-component.
13. MOPA apparatus, comprising:
a seed pulse generator arranged to generate a plane-polarized pulse to be amplified, the pulse having a fundamental frequency;
an optical arrangement for dividing the pulse into first and second plane-polarized pulse-components having polarization orientations at 90-degrees to each other;
a polarization-maintaining fiber-amplifier for amplifying the first and second plane-polarized pulse-components thereby providing first and second amplified plane-polarized pulse-components;
an optical arrangement for directing the first and second amplified plane-polarized pulse-components along respectively first and second separate optical paths; and
a first optically nonlinear crystal disposed in the first optical path and arranged for type-1 frequency-doubling the first amplified plane-polarized pulse-component, thereby generating a first frequency-doubled plane-polarized pulse-component having a frequency which is the second harmonic of the fundamental frequency.
14. The apparatus of claim 13 , further including an optical arrangement for combining the first and second optical paths into a common path, and a second optically nonlinear crystal located in the common path.
15. The apparatus of claim 14 wherein the second optically nonlinear crystal is arranged for generating a frequency-tripled pulse having a frequency which is the third-harmonic of the fundamental frequency from the first frequency-doubled plane-polarized pulse-component and the second amplified plane-polarized pulse-component.
16. The apparatus of claim 15 , further including an arrangement for temporally separating the first and second plane-polarized pulse-components prior to amplification in the fiber-amplifier, and wherein there is difference in length between the first and second optical paths selected such that the first frequency-doubled plane-polarized pulse-component and the second amplified plane-polarized pulse-component are temporally overlapped prior to the frequency-tripled pulse generation.
17. The apparatus of claim 14 , further including an arrangement for temporally separating the first and second plane-polarized pulse-components prior to amplification in the fiber-amplifier, and wherein there is difference in length between the first and second optical paths selected such that the first frequency-doubled plane-polarized pulse-component and the second amplified plane-polarized pulse-component are temporally overlapped prior to entering the second optically nonlinear crystal.
18. The apparatus of claim 17 , further including a third optically nonlinear crystal disposed in the first optical path and arranged for type-1 frequency-doubling the second amplified plane-polarized pulse-component, thereby generating a second frequency-doubled plane-polarized pulse-component having a frequency which is the second harmonic of the fundamental frequency and wherein the second optically nonlinear crystal is arranged for generating a frequency-quadrupled pulse having a frequency which is the fourth harmonic of the fundamental frequency from the first and second frequency-doubled-plane polarized pulse components.
19. The apparatus of claim 13 , further including a second optically nonlinear crystal disposed in the first optical path and arranged for type-1 frequency-doubling the second amplified plane-polarized pulse-component, thereby generating a second frequency-doubled plane-polarized pulse-component having a frequency which is the second harmonic of the fundamental frequency, and an optical arrangement for combining the first and second optical paths into a common path, and a third optically nonlinear crystal located in the common path and arranged for generating a frequency-quadrupled pulse having a frequency which is the fourth harmonic of the fundamental frequency from the first and second frequency-doubled-plane polarized pulse components.