Non-Linear crystals

Non-linear Crystals, also called LNO crystals (for non-linear optics crystals) are popular in laser manufacturing due their ability to change the properties of light.

As their name suggest they exhibit non-linear optical properties (see explanation at the bottom of the page)  which result in light characteristics modification while it is traveling through the crystals.

Non-linear crystals, also shows birefringence, meaning that the refractive index will vary with the polarisation of the light.  It is important to respect phase matching conditions when using them.

non-linear crystals

Chart of the most common NLO crystals we provide :

  • Short name
  • LBO
  • BBO
  • KTP
  • LiNBO3
  • Chemical name
  • Lithium triborate
  • Beta barium borate
  • potassium titanyl phosphate
  • Lithium Niobate
  • Details
  • – good second-harmonic generation (SHG)
    – good sum-frequency generation (SFG)
    – Broad transparency range from 160nm to 2600nm
    -High damage threshold
    – Wide acceptance angle
  • -Lower non-linear coefficient than LBO
    -broader transparency range than LBO in the mid-IR
    – lower absorption in the UV and visible than LBO
    – higher damage threshold than LBO
  • – Non-linear coefficient @1064nm is 1.5 times that of BBO
    – SHG @ 1064nm is 80%
    – lower damage threshold than BBO crystals
  • -Large Electro-optics (E-O) coefficient
    – Large Acousto-optics (A-O) coefficient
  • usage
  • – laser frequency doubling
    – advanced optical device
  • – laser frequency doubling & tripling
    – advanced optical device
    – Q-switch
  • – frequency mixing of Nd laser for blue output
    – frequency doubling of Nd lasers for green / red output
    – optical switches
  • – frequency doubling for > 1µm wavelengths
    – Electro optic modulators
    – Q-switch

Crystals delivery

Crystals can be provided in many shapes likes rods, plates or cubes. AR & HR coatings can be applied on specific faces.

  • Transmitted wavefront distortion : better than Lambda /4
  • Clear aperture : better than 90%
  • Flatness : lambda /8
  • Aspect :  S&D 20/10
  • Parallelism : < 20 arc second
  • Perpendicularity : < 5 arc minutes
  • Orientation tolerance : < 0.5°

What is non-linearity in optical crystals ?

Non-linear optics refer to optics for which the light output will not be directly proportional to the incident light intensity.

For example if you increase the incident light intensity of a linear optics light by a factor of ten, you’ll notice the same proportional (x10) increase in the output. This is not the case for non-linear optics.

This non-linearity can lead to other changes in light property, like frequency conversion, harmonic generation,  non-linear amplification etc..

The characteristics of the non-linear crystals are linked with the crystal elements themselves, it is therefore important to chose the good crystal matching a specific need.