Laser damage threshold
In optical applications and experiments, an important factor in selecting optical components is whether they can withstand the effects of optical radiation, which is particularly important in high-power laser applications. There are three main types of damage to optical components caused by optical radiation: material chemical bond damage directly caused by extremely high peak power; The second is dielectric breakdown caused by short pulse laser radiation; The third is the thermal effect caused by light absorption. The parameter that determines the ability of an optical component to withstand light radiation under short pulse laser is called the laser damage threshold, which represents the maximum energy density (pulsed light source) or maximum optical power density (continuous light source) that the optical component can withstand. The unit is usually expressed in W/cm2 and J or cm2.
This article will discuss the laser damage threshold corresponding to different types of laser sources.
continuous-wave laser
The damage to optical components caused by continuous laser is mainly due to thermal reactions, and the laser damage threshold is represented by the highest tolerable laser density power. For example, the power density of a 50mw Nd: YAG laser with a wavelength of 1064nm and a beam diameter of 0.8mm was calculated.
First, calculate the spot area: Spot area=r2=3.14x (0.4mm) 2=5.024x10-3cm2.
Then calculate the laser power per unit area: power density=laser power/spot area=9.95W/cm2.
Compare it with the damage threshold of optical components to determine if the optical components are suitable.
It is worth mentioning that the laser damage threshold of optical components is directly proportional to the wavelength. The laser damage threshold at 532nm is approximately half of that at 1064nm.
pulsed laser
Under the action of pulsed laser, the damage threshold of optical components is usually represented by the maximum tolerable pulse energy density. For pulse lasers with pulse widths between microseconds and nanoseconds, the damage threshold is proportional to the square root of the pulse width in the time domain. For example, under a 1-second pulse, the damage threshold of optical components is 10 times higher than under a 10ns pulse. If the damage threshold of the optical element is 2j/cm2 under a 10ns pulse, then under the same wavelength of a 1s laser pulse, the damage threshold of the optical element is 2j/cm2 * (10-6sec/10x10-9sec) 1/2=20j/cm2.
ultrafast laser
For ultrafast lasers with time-domain widths of picoseconds and femtoseconds, laser pulses have high peak power and electric field strength, which can break the chemical bonds of irradiated materials and cause medium disintegration. The damage threshold of ultrafast laser cannot be calculated based on the damage threshold of nanosecond pulses, and the damage mechanism is closely related to the pulse width, making it difficult to characterize.
This article will discuss the laser damage threshold corresponding to different types of laser sources.
continuous-wave laser
The damage to optical components caused by continuous laser is mainly due to thermal reactions, and the laser damage threshold is represented by the highest tolerable laser density power. For example, the power density of a 50mw Nd: YAG laser with a wavelength of 1064nm and a beam diameter of 0.8mm was calculated.
First, calculate the spot area: Spot area=r2=3.14x (0.4mm) 2=5.024x10-3cm2.
Then calculate the laser power per unit area: power density=laser power/spot area=9.95W/cm2.
Compare it with the damage threshold of optical components to determine if the optical components are suitable.
It is worth mentioning that the laser damage threshold of optical components is directly proportional to the wavelength. The laser damage threshold at 532nm is approximately half of that at 1064nm.
pulsed laser
Under the action of pulsed laser, the damage threshold of optical components is usually represented by the maximum tolerable pulse energy density. For pulse lasers with pulse widths between microseconds and nanoseconds, the damage threshold is proportional to the square root of the pulse width in the time domain. For example, under a 1-second pulse, the damage threshold of optical components is 10 times higher than under a 10ns pulse. If the damage threshold of the optical element is 2j/cm2 under a 10ns pulse, then under the same wavelength of a 1s laser pulse, the damage threshold of the optical element is 2j/cm2 * (10-6sec/10x10-9sec) 1/2=20j/cm2.
ultrafast laser
For ultrafast lasers with time-domain widths of picoseconds and femtoseconds, laser pulses have high peak power and electric field strength, which can break the chemical bonds of irradiated materials and cause medium disintegration. The damage threshold of ultrafast laser cannot be calculated based on the damage threshold of nanosecond pulses, and the damage mechanism is closely related to the pulse width, making it difficult to characterize.