Optical fiber amplifier, light source device, exposure device, object inspection device, and treatment device

Abstract

A polarization state adjusting optical element is formed by a ½ wavelength plate and a ¼ wavelength plate and its polarization direction and elliptic degree are adjusted. By adjusting the polarization state adjusting optical element in advance, even if the output of a pump light source is changed, the polarization characteristic (polarization direction and elliptic degree) of the output light of an FDFA amplifier will not not change or the change is sufficiently small. In this state, a polarization state adjusting optical element adjusts the polarization state of the laser beam coming into a wavelength conversion optical system so that the wavelength conversion optical system has the maximum conversion efficiency. Thus, it is possible to provide an FDFA having a small change of the polarization state of the output light even if the pump light intensity is changed.

1 . An optical fiber amplifier, wherein the polarization state of an input light is adjusted in such a way that the polarization state of an output light will not change even if an amplification factor is changed. 
     
     
         2 . An optical fiber amplifier, comprising a polarization state adjusting optical element which adjusts the polarization state of an input light in such a way that the polarization state of an output light will not change even if an amplification factor is changed. 
     
     
         3 . A light source device which optically amplifies a laser beam generated from a laser light source by an optical fiber amplifier or optical fiber amplifiers and allows the optically amplified light to be incident on a wavelength conversion optical system to obtain an output light having a predetermined wavelength, comprising light separation means for taking out a portion of the output light as a monitor light, and a light intensity adjusting device which manipulates the intensity of an excitation light supplied to at least one of the optical fiber amplifiers in such a way that the intensity of the monitor light taken out by the light separation means is kept at a target value, wherein the optical fiber amplifier of which an amplification factor is changed by the excitation light whose intensity is manipulated is an optical fiber amplifier according to  claim 1 . 
     
     
         4 . A light source device which optically amplifies a laser beam generated from a laser light source by an optical fiber amplifier and allows the optically amplified light to be incident on a wavelength conversion optical system to obtain an output light having a predetermined wavelength, comprising light separation means for taking out a portion of the output light as a monitor light, and a light intensity adjusting device which manipulates the intensity of an excitation light supplied to the optical fiber amplifier in such a way that the intensity of the monitor light taken out by the light separation means is kept at a target value, wherein a polarization state adjusting optical element is arranged between the laser light source and the optical fiber amplifier. 
     
     
         5 . The light source device according to  claim 4 , wherein the polarization state adjusting optical element has a ¼ wavelength plate and a ½ wavelength plate. 
     
     
         6 . The light source device according to  claim 4 , wherein a plurality of optical fiber amplifiers are provided and the monitor light taken out by the light separation means is supplied to at least one of the plurality of the optical fiber amplifiers. 
     
     
         7 . The light source device according to  claim 4 , wherein the polarization state adjusting optical element is arranged between the laser light source and the optical fiber amplifier on which a laser beam emitted from the laser light source is first incident. 
     
     
         8 . An exposure device comprising a light source device according to  claim 3 , a mask supporting portion which holds a photomask having a predetermined exposure pattern, an object holding portion which holds an exposed object, an illumination optical system which illuminates the photomask held by the mask supporting portion with a light emitted from the light source device, and a projection optical system which projects the light from the photomask onto the exposed object held by the object holding portion. 
     
     
         9 . An exposure device comprising a light source device according to  claim 4 , a mask supporting portion which holds a photomask having a predetermined exposure pattern, an object holding portion which holds an exposed object, an illumination optical system which illuminates the photomask held by the mask supporting portion with a light emitted from the light source device, and a projection optical system which projects the light from the photomask onto the exposed object held by the object holding portion. 
     
     
         10 . An object inspection device comprising a light source device according to  claim 3 , a supporting portion which holds an object, a detector which receives a projection image of the object for detection, an illumination optical system which illuminates the object held by the supporting portion with a light emitted from the light source device, and a projection optical system which projects the light from the object onto the detector. 
     
     
         11 . An object inspection device comprising a light source device according to  claim 4 , a supporting portion which holds an object, a detector which receives a projection image of the object for detection, an illumination optical system which illuminates the object held by the supporting portion with a light emitted from the light source device, and a projection optical system which projects the light from the object onto the detector. 
     
     
         12 . A polymer crystal processing device comprising a light source device according to  claim 3 , an optical system which guides a laser beam emitted from the light source device to a polymer crystal as a processed object and focuses the laser beam onto a processed location of the polymer crystal, and a mechanism which changes a relative position of the optical system and the polymer crystal. 
     
     
         13 . A polymer crystal processing device comprising a light source device according to  claim 4 , an optical system which guides a laser beam emitted from the light source device to a polymer crystal as a processed object and focuses the laser beam onto a processed location of the polymer crystal, and a mechanism which changes a relative position of the optical system and the polymer crystal. 
     
     
         14 . A light source device which optically amplifies a laser beam generated from a laser light source by an optical fiber amplifier or optical fiber amplifiers and allows the optically amplified light to be incident on a wavelength conversion optical system to obtain an output light having a predetermined wavelength, comprising light separation means for taking out a portion of the output light as a monitor light, and a light intensity adjusting device which manipulates the intensity of an excitation light supplied to at least one of the optical fiber amplifiers in such a way that the intensity of the monitor light taken out by the light separation means is kept at a target value, wherein the optical fiber amplifier of which an amplification factor is changed by the excitation light whose intensity is manipulated is an optical fiber amplifier according to  claim 2 .