Reducing the spectral bandwidth of lasers

Patent metadata

Field	Value
Publication number	US-8964798-B2
Application number	US-201313939000-A
Country	US
Kind code	B2
Filing date	Jul 10, 2013
Priority date	Jul 12, 2012
Publication date	Feb 24, 2015
Grant date	Feb 24, 2015

Abstract

A laser system for semiconductor inspection includes a fiber-based fundamental light source for generating fundamental light that is then converted/mixed by a frequency conversion module to generate UV-DUV laser light. The fundamental light source includes a nonlinear chirp element (e.g., a Bragg grating or an electro-optic modulator) that adds a nonlinear chirp to the seed light laser system prior to amplification by the fiber amplifier(s) (e.g., doped fiber or Raman amplifiers). The nonlinear chirp includes an x 2 or higher nonlinearity and is configured to compensate for the Self Phase Modulation (SPM) characteristics of the fiber-based amplifiers such that fundamental light is generated that has a spectral E95 bandwidth within five times that of the seed light. When multiple series-connected amplifiers are used, either a single nonlinear chirp element is provided before the amplifier string, or chirp elements are included before each amplifier.

First claim

The invention claimed is:

1. A laser system for generating laser output light having a nominal UV-DUV output frequency, the laser system comprising:
a fiber-based fundamental light source for generating fundamental light at a nominal fundamental frequency including:
one or more seed lasers including means for generating seed light having an initial peak power and an initial spectral bandwidth, and for transmitting the seed light along an optical path;
one or more amplifiers di…

Assignees

• Kla Tencor Corp

Inventors

• Armstrong J Joseph

Classifications

• H01S3/02

  Electricity · mapped topic

• H01S3/10 Primary

  Electricity · mapped topic

• H01S3/30

  Electricity · mapped topic

• H01S3/06758 Primary

  Electricity · mapped topic

• G01N21/00

  Physics · mapped topic