|Laser Damage Threshold|
|ㆍ작성일: 2011-08-10 (수) 17:08||ㆍ조회: 315|
Continuous Wave Lasers
For continuous wave (CW) lasers the damage threshold can be calculated from the peak power and beam diameter. For example, to calculate the power density of a 50 mW Nd:YAG laser at 1064 nm with a 0.8 mm beam diameter, first calculate the beam area in terms of centimeters:
For pulsed lasers in the range of µsec to nsec, the energy density varies as a function of the square root of the time domain. As a rule of thumb, an optic can withstand 10 times more energy when used with a 1 µsec pulsed laser than a 10 nsec pulsed laser. Suppose, for instance, that the damage threshold is rated at 2 J/cm2 for 10 nsec pulses, but your laser has a 1 µsec pulse length. This means that at the 1 µsec time domain (10-6 sec compared to 10 x 10-9 sec), the optic can withstand 10 times more energy (20 J/cm2).
For Ultrafast pulsed lasers in the psec to fsec regime, the electric field of the pulse attacks the electronic bonds of the dielectric coating. Peak powers can be quite high. Our UF.25 Ultrafast 45° mirror has been laboratory tested and found to have a damage threshold of 1 TW/cm2 with 100 fsec pulses at 5 Hz at 800 nm.
출처 : Newport "Technical Notes"