New High Power Laser Medium Index Matching Reduces Parasitic Lasing in Cryogenic Environments

Technology #33261

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A schematic drawing of a cylindrical disc laser gain medium having a perimetrical edge entirely coated with an ASE-absorbing epoxy composition, disposed in a cryocoolerA schematic drawing of a rectangular laser gain medium having a perimetrical edge partially coated with an ASE-absorbing epoxy composition, disposed in a cryocooler
Zenghu Chang, Ph.D.
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Eric Cunningham, Ph.D.
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Yi Wu, Ph.D.
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Patent Protection

US Patent Pending

A common problem in large-aperture, high-power, solid state amplifiers is parasitic, or transverse, lasing. When this phenomenon occurs, the energy stored in the amplifier quickly drains, effectively clamping the gain accessible to the intended longitudinal amplification process.

Currently available methods for reducing parasitic lasing involve the use of absorbing thin films, optical coatings, and index-matching approaches to reduce the amplified spontaneous emission (ASE). Absorption is accomplished by cladding selected boundaries of the gain medium with material that efficiently absorbs incident ASE photons, while index-matching involves bonding various optical materials to the ends of the gain medium. These approaches are all limited by the incompatibility of absorbing thin films, optical coatings, and index-matching approaches in extreme environments, such as high vacuum and/or cryogenic settings.

UCF researchers have developed an innovative method that reduces and/or eliminates gain clamping in a solid-state laser and amplifier systems and works with other index-matching methods. The design works well with standard cladding/coating materials that employ either tunable index of refraction or tunable absorption materials, and with materials that have no existing index-matching procedures available. This technique can also be used as part of an amplifier offering the benefits of both cryogenic cooling and anti-transverse lasing.

Technical Details

This novel system provides a solid-state laser/amplifier gain medium that prevents parasitic lasing and is compatible with operation in evacuated and cryogenic environments. The gain medium is comprised of a perimetrical edge with an ASE-absorbing epoxy composition, with an index refraction that matches the gain medium’s index of refraction, applied on a portion of the edge. By bonding a light-absorbing, refractive index-matched material to the edges of the laser gain medium, the ASE in the transverse direction can be coupled out to prevent the build-up of parasitic oscillation. This technique reduces the strength of the Fresnel reflections and adds high absorption losses, both of which increase the losses in the transverse direction. Different epoxies with high and low refractive indexes are combined in predetermined amounts to create an optical refractive index that closely matches the laser gain medium. To enhance the absorption power, super fine metal particles with absorption at ASE wavelengths may be added to the epoxy base.


  • Reduces or eliminates gain clamping
  • Improves large-aperture, high-power, solid state amplifier operation
  • Works in a variety of conditions
  • Can work with other index-matching approaches
  • Can be used in an amplifier in extreme environments


  • High-power solid state laser amplifiers
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