frequencytripled

Frequencytripled refers to light whose frequency has been multiplied by three, a process known in optics as third-harmonic generation (THG). It is commonly described as a frequency tripling of the input light. The process typically requires high peak powers, produced by ultrafast pulsed lasers, and occurs in nonlinear materials that exhibit a sizable third-order optical susceptibility.

Mechanism: The third-order polarization P(3) ∝ χ^(3) E^3 generates radiation at 3f. Efficient frequencytripling relies on phase matching to keep the generated wave in phase with the driving field. This can be achieved with birefringent crystals such as beta barium borate (BBO) or lithium triborate (LBO), or by quasi-phase matching in periodically poled materials. In some systems, a cascaded sequence of second-harmonic generation followed by sum-frequency generation can produce a similar outcome.

Applications and notes: Frequencytripling is used to produce ultraviolet light from common infrared lasers, notably converting 1064 nm light to 355 nm for microfabrication, spectroscopy, and laser micromachining. In scientific imaging, THG provides contrast through intrinsic material properties without exogenous labels. Practical implementations require careful control of beam quality, pulse duration, and damage thresholds; efficiencies are typically modest and strongly depend on wavelength, crystal quality, and phase-matching conditions.