ADP (Ammonium Dihydrogen Phosphate) is a commonly used nonlinear crystal in laser technology for frequency conversion. ADP has a high nonlinear coefficient and a low absorption coefficient, making it an efficient material for second harmonic generation (SHG) and sum frequency generation (SFG) processes.
In SHG, the frequency of a laser beam is doubled by passing it through an ADP crystal. This process is used to generate light in the ultraviolet range, which is useful in applications such as fluorescence microscopy and laser spectroscopy.
SFG involves combining two laser beams of different wavelengths to create a new beam with a frequency equal to the sum of the input frequencies. ADP is often used as the nonlinear crystal in SFG because of its high efficiency and low absorption. SFG is used in a range of applications, including in Raman spectroscopy and in the production of visible and ultraviolet light.
ADP is a birefringent crystal, meaning that it has different refractive indices for light polarized in different directions. This property allows ADP crystals to be used as optical isolators, which are devices that allow light to pass through in one direction but block it in the opposite direction. ADP optical isolators are used in telecommunications and in laser systems to protect the laser from feedback that can cause instability and reduce performance.
|Transparency range, µm||0.18 - 1.53|
|Lattice parameters, Å||a=b=7.499; c=7.549|
|Refractive index at 407.8 nm :||no=1.53925; ne=1.49123|
|at 632.8 nm||no=1.52195; ne=1.47727|
|at 1064 nm||no=1.5071; ne=1.4685|
|Non-linear coefficient at 1.064 µm, pm/V||d36 = 0.47|
|Optical damage threshold, MW/cm2||500 (1064 nm, 60 ns)|