YAG stands for yttrium aluminum garnet, which is a synthetic crystal. Nd:YAG is an artificial cubic garnet crystal. YAG crystals were created shortly after ruby laser discovery. They have high gain and other unique properties which make them universal for a lot of different applications. YAG crystals increase the stability of the source, its efficiency and lifespan, reduce size and power consumption.
There are certain limitations connected with the high gain and the safety of the operating fluence. Mode-lock property creates pulses of very different widths – nanosecond to picoseconds, which enables it to make wide-ranging peak power for various applications.
YAG laser is a solid state diode pumped laser, its beam is in mid infra-red range and its wavelength is 1064 nm. Nd:YAG is an outstanding solution for scientific laser systems because it can reach extremely high powers in a pulsed mode, which is used in the oscillators to produce series of very short pulses to perform research with femtosecond time resolution.
Nd:YAG laser may be used with a frequency doubler, in this case its wavelength is 532 nm and its output power is lower.
In terms of applications, yag laser systems are very versatile. It has been widely used in the military, for example, for rangefinding or for target designation.
On the other hand, as mentioned before its pulse width and high power, it is extremely useful for scientific purposes, or as a pumping source for other lasers.
Medicine is another field where Nd:YAG is frequently used, namely dermatology and ophthalmology. Commercial purposes include applications such as ablation, spectroscopy, marking, nondestructive testing and others. Moreover, it is an optimal cost-efficient laser.
Key feature of the YAG lasers is its resilience to different environmental conditions; hence it suits perfectly well for remote sensing, bathymetry, gated imaging illumination, atmospheric and ocean studies, etc.
Other lasers or nonphotonic techniques may be used for most of the applications mentioned above, for example, diode or CO2 lasers. Nd:YAG allows to perform a broad range of applications, because of its one-of-a-kind properties, and also, not many lasers have an ability to function efficiently with diode pumping and to switch between pulsed or CW mode.
Advanced laser systems, technology and equipment for LIDAR
LIDAR (light detection and ranging) is a laser technology used for optical remote sensing which allows one to analyze scattered light properties in order to obtain certain information about a distant object.
These advanced laser systems are often used, for example, to collect precise information about Earth surface and its characteristics. The sensor sends out a pulse of light to travel to an object, it reflects off the object and travels back. When the light clashes into an object, the sensor detects the reflected pulse. Then it measures the time necessary for the reflected pulse to return. The light pulse travels with the speed of light which is known and constant; hence, the time is easily converted into distance or as it is called – the range. The information on the position and angle of the laser equipment allows calculating exact coordinates of the object reflected.
LIDAR technology can be applied in a lot of different areas, from geographical mapping to robotics due to its high configuration capabilities and wavelengths.
There are different types of LIDARs: rangefinder, DIAL and Doppler.
Rangefinders measure a distance between a sensor and a solid object.
DIAL (differential absorption) measures chemical concentrations in the atmosphere (ozone, water vapor, pollution). It emits pulses with two different wavelengths which are set in a specific way, so that a molecule can absorb one of them, but the other can’t. This way the molecule concentration is deduced.
Doppler technique measures an object velocity. When a light pulse travels to a moving object, its wavelength changes a little, and it is called Doppler shift. When the object is moving away from the sensor, the reflected wavelength will be longer, and when the object is moving towards the sensor, the reflected wavelength will be shorter.