Wavemeter for gas discharge laser
View Patent ↗An optical configuration to illuminate an etalon in a laser wavemeter with a minimum level of light intensity. The system includes optical components to direct a portion of the laser output beam representing the entire cross section of the beam, through an etalon positioned in an etalon housing and onto a photodetector. A first lens condenses the size of the beam sample, and a second lens re-collimates the beam which then passes into the etalon housing, ensuring that all of the spatial components of the beam are adequately sampled. A diffractive diffusing element is incorporated into the optical path. In a preferred embodiment, the diffractive diffusing element is placed within the etalon housing between said plano-concave lens and the etalon. In another preferred embodiment, the diffusing element is located up stream but outside the housing in the optical path.
1. A wavemeter for measuring wave properties of a laser beam of a gas discharge laser, said wavemeter comprising:
A) a first optical train, comprising at least two optical elements, for converting a portion of said laser beam into a substantially collimated sample beam spatially representative of the laser beam;
B) a diffractive diffusing element configured to diffuse said sample beam into a diffused beam which is expanding at angles of less than 10 degrees;
C) an etalon system positioned in said diffused beam, said etalon system comprising:
1) an etalon housing, and
2) two windows permitting light to enter said housing, and
3 2) an etalon positioned within said housing;
D) a detector array; and
E) a second optical train, comprising at least one focusing optical element, for focusing a beam exiting said etalon system onto said detector array;
wherein said etalon produces interference fringe patterns on said detector array, said fringe patterns being indicative of wavelength and bandwidth of said laser beam of said gas discharge laser.
2. A wavemeter as in claim 1 wherein said diffractive diffusing element is a diffractive lens array.
3. A wavemeter as in claim 2 wherein said diffractive lens array is configured to scatter light within an angle of about 5 degrees.
4. A wavemeter as in claim 3 wherein said lens is configured to scatter light within an angle of about 2 degrees in a first dimension and about 4 degrees in a second dimension.
5. A wavemeter as in claim 1 wherein said first optical train comprises condensing lens and a recollimating lens for cross section reduction of the sample beam.
6. A wavemeter as in claim 1 wherein said etalon comprises an upper plate and a lower plate and three fused silica spacers separating said upper and plate.
7. A wavemeter as in claim 6 wherein said spacers are about 934 micrometer±1 micrometers thick.
8. A wavemeter as in claim 6 wherein said upper plate comprises a support flange for supporting said upper and lower plates.
9. A wavemeter as in claim 8 wherein said upper and lower plates and said spaces are held together by optical contact.
10. A wavemeter as in claim 1 wherein said diffractive diffusing element is configured to diffuse said sample beam into a beam substantially all of which is diverging at angles of less than 2 degrees in a first direction and diverging at angles of less than 4 degrees in a second direction perpendicular to said first direction.
11. A wavemeter as in claim 1 wherein said at least two optical elements in said first beam train are two lenses.