Coherence of XeCl laser radiation (original) (raw)
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The coherence factors of excimer laser radiation in projection lithography
Journal of Vacuum Science & Technology B: Microelectronics Processing and Phenomena, 1989
The spatial coherence of the excimer laser radiation seriously affects the quality of the images being reproduced by diffraction limited optics in photolithography. It is shown that the coherence parameters of excimer laser radiation exceed the necessary level in 102–103 times. To decrease the coherence down to the optimal level a fly’s eye element is used. The concept of Kirchhoff integrals has been applied to calculate the mutual intensity function transformation by the illuminator of the projection system equipped with fly’s eye element.
Investigation of the characteristics of an excimer laser with a narrow emission line
Soviet Journal of Quantum Electronics, 1990
An investigation was made of the spatial coherence of excimer lasers in different resonator geometries. Lasing with a spectral width of 5 nm was obtained in a scheme using a grating in the autocollimation regime and a four-prism telescope. A discussion is given of the questions involved in employing excimer lasers having a narrow laser emission line in photolithographic projection systems.
Repetition-rate influence on the beam quality of a XeCl excimer laser
Optics Communications vol. 167, pp. 291-298 (1999), 1999
The results of beam quality measurements of a XeCl (λ=0.308 μm) laser, equipped with a generalised self-filtering unstable resonator (GSFUR), while operating in the burst mode at repetition rates of up to 50 Hz are presented. In particular, the behaviour of the laser-energy distribution (both in the near- and far-field) and of the beam-angular stability vs. the repetition rate was measured. The time evolution of the divergence within the single laser pulse was also measured. The GSFUR showed its remarkable ability to achieve a nearly diffraction-limited divergence since the beginning of the laser pulse, and, most importantly, to maintain the values of the times diffraction-limit (TDL) number, of the M2 parameter and of the beam angular stability (BAS) independent of the repetition rate. The BAS resulted in fluctuations smaller than one third of the beam divergence.
Enhanced coherence x-ray laser experiments and simulations
1993
This is a preprintof a paperintextdedforpublicadon in ajournalorproceedings. Since changesmay be madebefore publi_ttion, this preprintis nude availablewith the undets_ that it will notbe cited or reproducedwithout the permissionof the author. t
We demonstrate ultra-high axial-resolution topography and tomography of multilayered objects using pseudo thermal light source, i.e., laser. The longitudinal spatial coherence (LSC) length of light was significantly reduced by synthesizing a pseudo thermal source with the combined effect of spatial, angular, and temporal diversity. Thus, generating a low spatially coherent (i.e., broad angular frequency spectrum) light source having narrow temporal frequency spectrum. The LSC length was reduced less than 10 micron using a very low magnification lens. Experimental results of optical sectioning of multilayer objects with high axial-resolution of the order of 4 micron was achieved which is comparable to broadband light source. The present system does not require any dispersion compensation optical system for biological samples as a highly monochromatic light source is used.
A study of the longitudinal laser modes of a semiconductor laser using optical coherence tomography
American Journal of Physics, 2006
Optical coherence tomography is used to demonstrate the modes of a semiconductor laser used in supermarkets. The experiment is low cost and can be adopted for an undergraduate or graduate physics laboratory. The results enable students to understand the voltage-current and optical power characteristics of a semiconductor laser, and provide insight into the nature of radiation below and above the lasing regions.
Development of a Laser-Pumped X-Ray Laser with Full Spatial Coherence
Journal of Plasma and Fusion Research, 2004
A laser-pumped x-ray laser with full spatial coherence has been developed for the first time. This x-ray laser has a wavelength of 13.9 nm and a beam divergence of 0.2 mrad. In the experiment, a seeding light from the first laser medium was amplified in the second medium, which worked as an active spatial filter. The observed beam divergence was close to the diffraction limited value within a factor of two. The seeding light was amplified in the second medium without refraction influence. The gain region of the second medium was far away from the target surface compared with that of the first medium, and was located in a region of considerably low density. From the measurement of visibility, it was found that the spatial coherent length was longer than the beam diameter. This means that this xray laser beam has full spatial coherence.