Single Mode and Multimode Pumps

Fiber Laser Pump Fundamentals:

Fiber laser pumps are used to excite electrons in the rare earth elements ytterbium, erbium and thulium after these elements have been doped into optical fiber. They are semiconductor laser diodes that are used to excite the electrons from their ground state to an increased energy state

Fiber laser pumps are coupled into rare earth element doped fiber in order to enable the fiber to act as an amplifying medium. This is the basis of the operation of a fiber laser. Multiple semiconductor laser diodes are coupled (spliced) into the fiber. These pumps are typically in the 915nm to 976nm range and can deliver from 500 milliwatts up to roughly 500 watts of optical power per laser diode. Pumps are typically categorized as either single mode or multimode pumps.

Single mode pump lasers are available with output power levels up to roughly 1 watt. They are typically stabilized using a fiber Bragg grating. This grating is embedded in the fiber. Single mode pumps offer much better beam quality than multimode pumps, but are limited in power and are far more expensive than multimode devices. They range in price from around $1,000 to $2,500 depending on the manufacturer and several packaging and optical parameters. They are usually offered in cooled butterfly packages and have single mode polarization maintaining fiber pigtails. Single mode pumps are used in the first amplification stage of a fiber laser.

Multimode fiber laser pumps offer optical output power levels up to 100's of watts. They are typically multi-chip emitters, meaning their are multiple laser diodes packaged into a single fiber coupled module. The multiple emitters are connected in series electrically. Optics are used to combine the multiple beams into a single high power output beam. Of course, multimode pumps have multimode fiber pigtails. They are far less expensive than their single mode counterparts. A single 50 watt fiber coupled multimode pump can be purchase for around $2,000.00 USD.