Methods of aligning a diffractive optical system and diffracting beams, diffractive optical element and apparatus

1. A method of aligning a diffractive optical system, the method comprising:

outputting an operating beam of radiation;

outputting an alignment beam of radiation; and

aligning the diffractive optical system using the alignment beam, wherein a wavelength range of the alignment beam is different than a wavelength range of the operating beam;

wherein the aligning comprises using a diffractive optical element to diffract the alignment beam and the operating beam in predetermined directions; and

wherein the alignment beam is directed during the aligning along a same optical path as the operating beam is to be directed along towards the diffractive optical element during operation of the diffractive optical system.

2. The method of claim 1 , wherein the predetermined directions are the same direction.

3. The method of claim 1 , wherein the wavelength range of the alignment beam is at longer wavelengths than the wavelength range of the operating beam, and wherein the alignment beam comprises infra-red radiation and the operating beam comprises soft X-ray radiation.

4. The method of claim 1 , further comprising generating the operating beam using a high harmonic generation optical source pumped by an optical source of the alignment beam.

5. The method of claim 4 , wherein the outputting the aligning beam is performed using an alignment beam having a lower intensity than used for generating the operating beam; and

wherein the method further comprises removing an alignment beam filter from a high harmonic generation optical source while performing the aligning, the alignment beam filter to be used during operation with the operating beam.

6. The method of claim 5 , wherein the providing the periodic structures comprises providing a grating.

7. The method of claim 1 , wherein the aligning the diffractive optical system comprises configuring optical elements of the diffractive optical system.

8. The method of claim 1 , further comprising providing the diffractive optical element with a first periodic structure with a first pitch and a second periodic structure with a second pitch so as to optimize the diffractive optical element.

9. The method of claim 8 , wherein the providing the first and second periodic structures comprises providing a multi-pitch periodic structure.

10. The method of claim 8 , further comprising orienting the periodic structures as coplanar.

11. The method of claim 8 , further comprising overlaying the periodic structures.

12. The method of claim 8 , further comprising interleaving the periodic structures.

13. The method of claim 8 , wherein:

the first periodic structure is formed at a region corresponding to the alignment beam's spot when projected on the diffractive optical element; and

the second periodic structure is formed at a region corresponding to the operating beam's spot when projected on the diffractive optical element.

14. A method comprising:

outputting a first beam having a wavelength range;

outputting a second beam in a same direction as the first beam, wherein the second beam has a different wavelength range than the wavelength range of the first beam;

directing the first and second beams along a same optical path; and

diffracting the first and the second beams using a diffractive optical element having a first periodic structure with a first pitch and a second periodic structure with a second pitch, wherein the pitches are selected to diffract the first and second beams in the same direction.

15. A diffractive optical system comprising:

a diffractive optical element configured to diffract an alignment and an operating beam in predetermined directions, the diffractive optical element comprising:

a first periodic structure with a first pitch; and

a second periodic structure with a second pitch, wherein the first and second pitches are selected to diffract the alignment and operating beams in the predetermined directions,

wherein the first periodic structure is formed at a first region corresponding to the alignment beam's spot when projected on the diffractive optical element; and

wherein the second periodic structure is formed at a second region corresponding to the operating beam's spot when projected on the diffractive optical element; and

wherein the alignment beam is directed during an alignment operation along a same optical path as the operating beam is to be directed along towards the diffractive optical element during operation of the diffractive optical system.

16. The system of claim 15 , further comprising generating the operating beam using a high harmonic generation optical source pumped by an optical source of the alignment beam.

17. The system of claim 16 , wherein:

the outputting the aligning beam is performed using an alignment beam having a lower intensity than that used for generating the operating beam;

the method further comprises removing an alignment beam filter from the high harmonic generation optical source while performing the aligning; and

the alignment beam filter to be used during operation with the operating beam.

18. The system of claim 15 , wherein the periodic structures comprise a grating.

19. The system of claim 15 , wherein the periodic structures are at least one of coplanar and interleaved.

20. The system of claim 15 , wherein the alignment beam comprises infra-red radiation and the operating beam comprises soft X ray radiation.