Ti:sapphire lasers are tunable lasers which emit red and near-infrared light in the range from 650 to 1100 nanometers, operating most efficiently at wavelengths near 800 nm.A Ti:sapphire laser is usually pumped with another laser with a wavelength of 514 to 532 nm.Femtosecond lasers work in pulse mode have short duration and high instantaneous power, enabling to process materials in very short time,and small spaces，is appropriate for processing materials.
Theotry
The main components of device are:
Ti:sapphire crystals
Gain medium.A kind of crystals with multiple degeneracy energy level of ,electronic energy level coupling with lattice vibrational level makes energy band of ground state and excited state broaden.The main absorption peak at 488 nm,gain wave band in the range from 650nm to 1200nm,so can produce 3fs ultra short pulse lasers.Peak power can be high in low energy condition when the duration of pulse is extremely short,this is advantageous to materials processing and materials repairing.
Pump source——Providing pump lasers for Ti:sapphire crystal.Wavelengths of pump souce which are usually used in the range from 514nm to 532nm,such as diode pumped Q-switched lasers,Nd:YAG frequency doubled lasers.
Prism——For dispersion compensation.We should compensate dispersion by providing oppsosite dispersion.Ti:sapphire belongs to positive dispersion materials,so there should be negative dispersion materials such as prism.
Feature
- Small thermal region
- High peak power
- Wide tuning range
- Stable performance
Application
- Transparent dielectric material processing
Ti:sapphire crystals produce 800nm laser lights which can be focused inside the materials and temperature around the focal spot is high so there are plasma,then lead to microburst.Mazur team at Havard University produced microcavities with nearly 300nm in diameter by using 800nm,100fs,0.5μJ pulse.Because the thermal region of femtosecond lasers is small, femtosecond lasers can be used to write optical grating precisely.
- Dual photon polymerization micro-machining
Ti:sapphire crystals prudouce 800nm,100fs,20nj laser lights which exceed the absorption threshold of dual photon,then polymerization reaction happens in partial part of the focus center where energy exceeds absorption threshold.Through this process,three-dimension structures can be produced.
- Ablating meral materials
200fs,800nm laser lights with different energy have different effect on abalting metal materials.In condiotion of low energy,phase change happens firstly on material subsurface,materials are ablated due to pressure produced by material subsurface while energy reachs to threshold.In condition of high energy,thermal ablation occurs firstly on material surface because of the melting and vaporization expansion of surface atmos.
Leave a Reply