Crystal laser gain media like Neodymium-doped Yttrium Lithium Fluoride (Nd:YLF) and Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) have a narrow gain spectral bandwidth. Optical beam amplifiers require many stages of gain in order make the beam entering the subsequent amplifier able to extract the stored energy. If individual commercial laser could be combined into a single more energetic "seed" beam, then extracting energy from fewer amplifiers could be accomplished with minimal Size, Weight And Power dissipation (SWAP).


This invention utilizes transmission gratings to combine lasers of the same wavelength into a single collinear output. The transmission grating can be an all-bulk structure fabricated in fused silica, silicon, diamond, silicon nitride, etc. The transmission grating can also have dielectric coatings to increase diffraction efficiency and optical bandwidth. This invention makes possible collinear overlapped beam- for same wavelengths spectrum and bandwidth depending on system requirements. It fits into system designs requiring same wavelength of narrow spectrum to be combined into one beam. This invention transmission grating is 99%+ efficient at the combining of each beam. To our knowledge this is higher than filter beam splitters and UN-polarized spectral beam combining. This invention can be used in industrial beam combining and any other application where combining same wavelength beams is to system performance advantage motivated by each laser itself which has its own internal beam irradiance limitations.


LLNL’s novel method of combining two or more same wavelength narrow bandwidth linearly polarized laser beams:

  1. Enables combination of narrow, same wavelength laser beams,
  2. 99%+ efficient in combining of each beam,
  3. Combining same wavelength laser sources enables a simpler system configuration for serviceability,
  4. Can be realized in a compact optical assembly.
Potential Applications
  • High power directed energy and industrial laser systems power scaled through the combination of multiple same wavelength beams.
Development Status

Current stage of technology development:  TRL 3 (March 2023)

US Patent Application No. 2022/0260843 TRANSMISSION GRATING BEAM COMBINER published 08/18/2022 (

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