What are DPSS Lasers?
A diode-pumped solid-state laser or DPSS Laser uses a solid-state gain medium to amplify the laser light when pumped by a laser diode (or array of diodes). The gain medium used is usually a thin rod or in the form of a thin disk. DPSS lasers can operate in both CW and Pulsed modes with output powers from a few mW to kW. The gain medium used in DPSS laser is formed by doping the crystal/glass with rare-earth ions such as neodymium, ytterbium, erbium, thulium, or praseodymium. The beam from DPSS lasers can have multiple colors based on the operation wavelength and can be used in a wide range of applications that include ablation, LIDAR, spectroscopy, particle imaging velocimetry (PIV), micromachining, and medical.
DPSS lasers provide a high beam quality, a long operational lifetime and are available in compact packages.
The internal structure of a DPSS laser
How does a DPSS laser work?
The pumping light from a laser diode is focused on the Solid State Gain Medium through a cylindrical lens (collimator). This cylindrical lens transforms the strongly diverging light beam into an aligned beam in a specific direction, i.e., into collimated light or parallel rays. The purpose of this cylindrical lens is to reduce the divergence and to reduce the spatial cross-section of the beam.
Erbium metastable state
Now, the ions (for example, Er3+ ions of the Erbium-doped gain medium) in the ground state absorb the optical energy and jump into higher energy states. From these higher states, the ions rapidly transit to a metastable state, which is the energy state between the ground state and higher energy states.
Sufficient optical pumping ensures the population inversion between the ground state and the metastable state and release more photons by striking ions in the metastable state. These photons will also reflect back and forth between the reflective surfaces and strikes more ions leads to more photons release. As the photon activity goes on increasing, there comes a time when a strong beam of laser light is obtained.
Specification of DPSS Lasers
Wavelength: Represents the wavelength of laser light emitted from a DPSS laser. The DPSS lasers are available in infrared to the ultraviolet range. The wavelength is represented in a nanometer (nm).
Tunable: Represents the wavelength tune-ability of the DPSS laser. The DPSS lasers are available both in tuneable and non-tuneable options.
Fiber-coupled: The DPSS lasers are available both in fiber couple or non-fiber couple options.
Operation mode: Represents the operation mode. The DPSS lasers are available both in continuous wave (CW) and pulsed mode operation.
Laser color: DPSS lasers are available from IR to deep UV spectrum.
Mode: Represents the mode of operation of laser light. It can be single-mode or multi-mode.
Laser gain medium: Represents the type of material used as the laser gain medium. It can be Nd: AG/ Nd:YLF/ Nd:YVo4/ Ti: Sapphire/ Erbium-doped. Mostly, the Nd:YAG is used as the laser gain medium.
Power: Represents the power output of the DPSS laser in the range of milliwatts to multiple kilowatts.
Pulse width: Represents the pulse duration of the DPSS laser working in pulsed mode of operation. Usually, it is a nanosecond.
Pulse energy: Represents the pulse energy of the DPSS laser working in pulsed mode of operation. Usually, it is represented in mJ (milli-joule)
Beam quality factor (M2): It is the measure of beam quality.