Pulsed Fiber Lasers
Frequently Asked Questions
Pulsed Fiber Lasers typically use either active or passive Q-switching to generate a train of laser pulses with durations in the order of 10s to100s of nanoseconds. In a typical Q-switching architecture intracavity lasing is modulated, thus curating the time windows where the resonator is open for lasing. This allows accumulation of population inversion in the off time and generation of high-energy laser pulses with short temporal profile when the gates are open. There is also a subset of pulsed fiber lasers that achieve pulsing through mode-locking that allows achieving sub-picosecond temporal domains in the creation of ultrashort pulses. We have a dedicated category for such ultrafast fiber lasers, which you can browse by selecting that particular category above.
A special component such as a saturable absorber is typically integrated with the design to achieve passive mode-locking in ultrafast fiber lasers. In some cases, the birefringence of the fiber itself is used. Mode-locking is the technique behind generating ultrafast laser pulses.
Unlike free-space lasers, many pulsed fiber lasers tend to emit unpolarized or partially polarized light. Unfortunately, for such lasers fixing it through external optics might also prove to be difficult since the polarization state of lasing modes might show inherent instability and can drift with temperature and other environmental factors.
In fiber lasers, Bragg grating mirrors are added to the fiber in order to amplify the signal. Therefore, the fiber itself acts as both the laser cavity and the gain medium. Fiber Bragg grating (FBG) is a periodic structure (segment of periodic variation of optical index) created inside the fiber core that causes the light to diffract, reflect or transmit based on the phase and wavelength. These periodic structures applied to the core of the optical fibers are typically a few millimeters or centimeters long with a period that is on the order of a wavelength or hundreds of nanometers. FBG acts as an effective optical filter in fiber optic devices including fiber lasers.
Compared to free-space pulsed lasers, fiber lasers are very compact and because the light is confined in a fiber, it can be easily coupled to other fibers and devices with minimal loss. Fiber lasers are also lighter than free-space lasers. This makes them easy to move around and work with. Given their compact and robust architecture fiber lasers have become a formidable competitor to other DPSS lasers for many applications including laser machine processing systems (laser engravers, laser cutters, laser welding machines, etc.).
Thanks to their flexibility, high pulse powers, and wide wavelength range pulsed fiber lasers are used in laser cutting, cleaning, marking, welding, and engraving. Some of the less popular applications of pulsed fiber lasers include LiDAR systems, sensing, and mapping.
Both types of lasers are commonly used in many machining applications including marking and cutting. However, the main difference lies in the quality of their performance and wavelength. Pulsed fiber lasers exhibit an overall higher performance and precision when it comes to cutting materials like copper and aluminum. The cost of operation is another huge difference between the two types of lasers. It is estimated that fiber lasers’ cost of operation is half that of CO2 lasers. This is primarily due to the longevity of fiber lasers compared with that of CO2 lasers which naturally age as the CO2 gas mixture deteriorates over time.
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