1540nm Lasers

Laser range finding is a term used to describe the process of determining the distance to a fixed object.  This process is essentially a simplified version of laser radar, and therefore has many of the same requirements as LiDAR lasers.  Since we are only considering stationary targets and distance is the only thing being measured, range finding lasers are always pulsed to measure the roundtrip time-of-flight and calculate the distance to the target. Eye safety is a concern for range finding, since they are typically operating over shorter distances and in more populated areas.  As a result, most of these lasers operate around 1.5 microns in wavelength, which is considered to be eye-safe because of the extremely high-water absorption.

Night vision active imaging is a process that combines traditional infrared imaging, with time-of-flight (TOF) lidar to produce 3-dimensional images without the need for visible lighting.  Active night vision imaging is typically used in high-end surveillance for both military and commercial security systems.  In this application, night vision lasers are usually pulsed, 1.5-micron sources with an internal photodiode. The integral photodiode allows for the InGaAs camera to be triggered each time a pulse is fired, ensuring accurate TOF measurements. Additionally, 1.5 microns is the ideal wavelength for night vision lasers because it is considered eye-safe, and therefore does not pose an optical hazard to any individuals who happen to pass through the beam path.

Similar to laser radar, 3D laser scanning is a non-contact, non-destructive technology that digitally captures the shape of objects creating a point cloud of data from the surface of an object.  The primary differentiator between laser radar and 3D scanning is the distance from the target. In this application, the laser is typically only few inches from the object under investigation. Short-pulsed lasers are typically used for this application, since the distance to the object is measured by looking at the roundtrip time-of-flight of each pulse, but frequency-modulated single-frequency fiber lasers can also be used for select applications.

LiDAR is the optical analog to traditional radar and allows for much higher bandwidth signals and therefore much higher resolution, due to the higher optical frequencies, compared to their radio wave counterparts. For stationary targets, where distance is the only thing being measured, short-pulsed LiDAR lasers are used to measure the roundtrip time-of-flight of each pulse and therefore calculate the distance to the target.  But, if a target is moving and you need to measure its speed, single frequency LiDAR lasers are required in order to accurately measure the Doppler shift and calculate the object’s speed.

Laser-induced breakdown spectroscopy (LIBS), is an atomic spectroscopy technique where a small portion of the material is ablated by a laser and the resultant plasma emission plume is analyzed by a spectrometer to determine its atomic structure.  LIBS is commonly used in mining, forensics, and scrap metal applications for sorting metals and other samples which can’t be analyzed using molecular techniques.  This process requires that the LIBS lasers have high pulse energy in order to vaporize the sample and induce the plasma emission.