There are many different wavelength tunable laser technologies, or Swept Sources, that combines Light Amplification by Stimulated Emission Radiation (LASER) with a wavelength selective feedback. The most common type of wavelength tunable laser is the External Cavity Laser (ECL) where the laser diode is combined with a diffraction grating that is external to the laser cavity. The ECL technology is well-established but has an inherent limitation on the scan rate. Lasing in ECLs is built from spontaneous emission as the wavelength is swept which causes a decrease in the imaging range (coherence length) as the scan rates increases.
The VCSEL technology is unique in its short optical cavity which results in a narrow linewidth and long coherence length. Together with the MEMS system this enables very rapid adiabatic wavelength tuning, thus maintaining the narrow linewidth and long coherence for sweep speeds up to several tens MHz. Hence to increase the imaging range and rate in 3D imaging the VCSEL technology can in many cases be an advantageous choice.