Double Lloyd’s mirror

Double Lloyd’s mirror is wavefront-splitting interferometer, working in XUV region.

1. base plate with three leveling micrometers; 2. common lateral travel for both mirrors; 3. common rotation stage for both mirrors; 4. vertical travel for mirror #2; 5.yaw rotation for mirror #2; 6. rotation of mirror #1; 7. Lloyd’s mirror #1; 8. Lloyd’s mirror #2; 9. horizontal travel for the microscope; 10. micrometer for microscope focusing; 11. haircross or mirror holder; 12. vertical travel of the haircross; haircross; 13. lateral travel of the haircross; 14. vertical actuator for the microscope; 15. roll rotation motor for mirror #2; 16. vertical travel for mirror #2; 17. horizontal travel for mirror #2.

Principle:

The double Lloyd’s mirror may function with both a spherical diverging source or with wavefront of a narrowly collimated beam. The flat mirrors forming the device are inclined to each other at a small angle δ. The images of the real source constitute two virtual sources, which in case of an ideally spherical wave are mutually coherent, and which may be considered as the sources in a virtual Young’s experiment configuration. The portions of the incident beam reflected by each mirror intersect after propagation a distance that is solely a function of the angle δ and of the beam divergence (or of the divergence of a spatially coherent section of the beam). In contrast to the “classical” Lloyds’s design, the distance mirror-detector, as well as period of the interference fringes, is independent of the angle of incidence of the illumination radiation on the mirrors.

Results:

Sample of raw interferogram made by double Lloyd’s mirror. Detector size is 27 x 7 mm, and the fringe period is equal to 50 nanometers.