Spatial filters for high power lasers
View Patent ↗A spatial filter includes a first filter element and a second filter element overlapping with the first filter element. The first filter element includes a first pair of cylindrical lenses separated by a first distance. Each of the first pair of cylindrical lenses has a first focal length. The first filter element also includes a first longitudinal slit filter positioned between the first pair of cylindrical lenses. The second filter element includes a second pair of cylindrical lenses separated by a second distance. Each of the second pair of cylindrical lenses has a second focal length. The second filter element also includes a second longitudinal slit filter positioned between the second pair of cylindrical lenses.
1. A double pass amplifier comprising:
a gain medium having an input portion and a reflective portion;
a reflective element optically coupled to the reflective portion;
a beam path optically coupled to the input portion;
a first set of cylindrical lenses disposed along the beam path, wherein the first set of cylindrical lenses are oriented orthogonally;
a set of longitudinal slit filters disposed along the beam path, wherein each of the longitudinal slit filters in the set are oriented orthogonally to each other;
a second set of cylindrical lenses disposed along the beam path, wherein the second set of cylindrical lenses are oriented orthogonally; and
an injection mirror positioned between the set of longitudinal slit filters and the second set of cylindrical lenses.
2. The double pass amplifier of claim 1 wherein the gain medium comprises Nd:Glass.
3. The double pass amplifier of claim 1 wherein each of the set of longitudinal slit filters comprise fused silica.
4. The double pass amplifier of claim 1 wherein a first lens of the first set of cylindrical lenses and a first lens of the second set of cylindrical lenses are characterized by a first focal length.
5. The double pass amplifier of claim 4 wherein a second lens of the first set of cylindrical lenses and a second lens of the second set of cylindrical lenses are characterized by a second focal length.
6. The double pass amplifier of claim 5 wherein the first focal length and the second focal length are a same focal length.
7. The double pass amplifier of claim 6 wherein a spacing between the set of longitudinal slit filters is a predetermined distance less than the same focal length.
8. The double pass amplifier of claim 6 wherein a distance between the first lens of the first set of cylindrical lenses and a second lens of the second set of cylindrical lenses is equal to twice the same focal length plus the predetermined distance.
9. The double pass amplifier of claim 1 wherein a beam aspect ratio is equal at a first lens of the first set of cylindrical lenses and a second lens of the second set of cylindrical lenses.
10. The double pass amplifier of claim 1 wherein each of the longitudinal slit filters of the set of longitudinal slit filters comprise fused silica.