Laser lithography system with improved bandwidth control
View Patent ↗A method and apparatus may comprise a seed laser, along with an amplifier laser amplifying the output of the seed laser. A bandwidth metrology module may provide a bandwidth measurement and a bandwidth error signal may be provided using a bandwidth set point. A differential timing system responsive to the error signal can selectively adjust a differential firing time between the seed laser and amplifier laser. A beam dimension and center wavelength control system may adjust a beam dimension, within the cavity of the seed laser, to select bandwidth, and may adjust center wavelength at the same time, using a plurality of beam expansion prisms and at least one other prism or other optical element in the cavity to select center wavelength.
1. An apparatus comprising:
a seed laser defining an optical cavity producing an output;
an amplifier laser receiving and amplifying the output of the seed laser and providing a laser system output;
a bandwidth metrology module measuring laser output bandwidth and providing a bandwidth measurement;
a center wavelength metrology module measuring laser output center wavelength and providing a center wavelength measurement;
a differential timing system responsive to said bandwidth measurement to selectively adjust a differential firing time between the seed laser and amplifier;
a dispersive optical element;
a first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element and selectively alter the laser output bandwidth; and
second and third prisms responsive to said center wavelength measurement to rotate relative to the dispersive optical element and selectively alter center wavelength.
2. The apparatus of claim 1 wherein:
the differential timing system adjusts the differential firing time to maintain bandwidth within a selected range of bandwidths.
3. The apparatus of claim 2 wherein:
the second and third prisms comprises a coarse center wavelength selection prism and a fine center wavelength selection prism.
4. The apparatus of claim 2 wherein:
the second and third prisms comprises a coarse center wavelength selection prism and a fine center wavelength selection prism.
5. The apparatus of claim 1 further comprising:
the second and third prisms adjust an angle of incidence of the beam upon the dispersive optical element.
6. The apparatus of claim 2 further comprising:
the second and third prisms adjust an angle of incidence of the beam upon the dispersive optical element.
7. The apparatus of claim 1 further comprising:
the system selectively adjusting the differential firing time comprising a fine bandwidth control adjustment; and
the first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element comprising a coarse bandwidth control adjustment.
8. The apparatus of claim 5 further comprising:
the system selectively adjusting the differential firing time comprising a fine bandwidth control adjustment; and
the first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element comprising a coarse bandwidth control adjustment.
9. The apparatus of claim 6 further comprising:
the system selectively adjusting the differential firing time comprising a fine bandwidth control adjustment; and
the first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element comprising a coarse bandwidth control adjustment.
10. An apparatus comprising:
a seed laser defining an optical cavity producing an output;
an amplifier laser receiving and amplifying the output of the seed laser and providing a laser system output;
a bandwidth metrology module measuring laser output bandwidth light and providing a bandwidth measurement;
a center wavelength metrology module measuring laser output center wavelength and providing a center wavelength measurement;
a differential timing system responsive to said bandwidth measurement to selectively adjust a differential firing time between the seed laser and amplifier;
a dispersive optical element;
a first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element and selectively alter the laser output bandwidth; and
a second prism and mirror responsive to said center wavelength measurement to rotate relative to the dispersive optical element and selectively alter center wavelength.
11. The apparatus of claim 10 wherein:
the differential timing system adjusts the differential firing time to maintain bandwidth within a selected range of bandwidths.
12. The apparatus of claim 10 wherein:
the second prism and mirror comprises a coarse center wavelength selector and a fine center wavelength selector.
13. The apparatus of claim 11 wherein:
the second prism and mirror comprises a coarse center wavelength selector and a fine center wavelength selector.
14. The apparatus of claim 10 further comprising:
a third prism operating in conjunction with the second prism to select center wavelength.
15. The apparatus of claim 11 further comprising:
a third prism operating in conjunction with the second prism to select center wavelength.
16. The apparatus of claim 10 further comprising:
the second prism and mirror adjust an angle of incidence of the beam upon the dispersive optical element.
17. The apparatus of claim 12 further comprising:
the second prism and mirror adjusts an angle of incidence of the beam upon the dispersive optical element.
18. The apparatus of claim 10 further comprising:
the system selectively adjusting the differential firing time comprising a fine bandwidth control adjustment; and
the first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element comprising a coarse bandwidth control adjustment.
19. The apparatus of claim 17 further comprising:
the system selectively adjusting the differential firing time comprising a fine bandwidth control adjustment; and
the first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element comprising a coarse bandwidth control adjustment.
20. The apparatus of claim 16 further comprising:
the system selectively adjusting the differential firing time comprising a fine bandwidth control adjustment; and
the first prism responsive to said bandwidth measurement to rotate relative to the dispersive optical element comprising a coarse bandwidth control adjustment.