Patent ID: 9025624
Filing Date: 2015-05-05
Classification: G03F

Abstract:
1. A beam generator comprising: a laser source configured to emit a laser beam; a short wavelength beam source configured to generate a short wavelength beam from the laser beam, the short wavelength beam being coherent with and having a wavelength shorter than that of the laser beam; and a spectral unit including a quartz plate and a first spectral layer coated on a first surface of the quartz plate, wherein the first spectral layer has a Brewster's angle greater than about 70° with respect to the laser beam wherein the short wavelength beam is reflected from the spectral unit without the laser beam, wherein the first spectral layer includes a ruthenium layer that has a predetermined thickness determined to cancel the infrared beam by destructive interference of first and second reflected infrared beams respectively reflected from top and bottom surfaces of the spectral layer when the infrared beam is incident onto the spectral layer at an incidence angle less than the Brewster's angle.