Modern lasers come in a seemingly endless variety ranging from diode lasers as small as a grain of rice to CO2 lasers the size of a refrigerator. The one thing that all of these lasers have in common is that they contain the three basic components of a laser: gain medium, resonator, and excitation source. If any of these three components are missing, it would be impossible to achieve threshold and start the lasing process. In this blog post, we are going to examine what happens when the resonator is removed from this equation, resulting in a device called an optical amplifier.
In both a laser and an optical amplifier, energy (the excitation source) is pumped into a gain material until there are more molecules or atoms in an excited energy state than the ground state, as shown in the figure below. Once this condition, known as population inversion, is satisfied the gain medium is now cable of supporting stimulated emission, which allows photons with energy equal to the energy level gap to be amplified. While a detailed analysis of how stimulated emission works, is beyond the scope of this blog post, a simplified explanation is that the incident photon “knocks” the atom or molecule down to a lower level causing an identical photon to be emitted by the medium in accordance with the laws of conservation of energy and momentum.
The difference between lasers and amplifiers comes in when we look at where the incident photon comes from. In a laser, the resonator “catches” a spontaneously emitted photon and then redirects it back into the gain medium over and over again until the laser gain threshold is reached initiating the lasing process. In an optical amplifier though there is no resonator, instead the photons come from an outside source known as a seed laser, which is then amplified via stimulated emission as it passes through the length of the amplifier. As a result, you can now take a lower power laser with your desired properties (linewidth, pulse width, beam profile, …) and increase its power without affecting it’s overall performance.
There are a wide variety of optical amplifiers available on the market including semiconductor tapered amplifiers, erbium-doped fiber amplifiers, and diode pumped solid state (DPSS) amplifiers just to name a few. While each of them has their advantages and disadvantages, DPSS amplifiers are typical viewed as the most versatile because they can be used with a very wide range of seed lasers ranging from high peak power q-switched lasers to single frequency continues wave lasers sources.
Here at RPMC Lasers we offer the neoVAN optical amplifier from neoLASE, in Germany, which is capable of producing up to 50W of output power at 1064nm. The neoVAN is available with up to 4 amplification stages, allowing you to produce up to 5x amplification while still maintain a TEM00 beam profile. The neoVAN series is an OEM type DPSS optical amplifier system to boost the pulse energy or average output power for a variety of applications. ranging from high peak power, short pulse picosecond lasers for micromachining applications or single frequency lasers for gravational wave detection.
For detailed technical specifications on our neoVAN series of optical amplifiers from neoLASE click here or talk to one of our laser experts today by calling 1-636-272-7227.