Switchable Ytterbium Fiber Laser Based on a Symmetrical Long-Period Fiber Grating

In this study, a switchable ytterbium-doped fiber laser based on symmetrical long-period fiber grating (LPFG) is presented. The LPFG is used as a wavelength-selective filter (WSF). Utilizing this WSF, the laser can emit one, two, or multiple stable output beams by adjusting the temperature on the LPFG from 20 °C to 600 °C. In addition, switching is also possible by adjusting the curvature of the LPFG from 0.399 to 0.709 m ^-1 . The symmetrical LPFG was fabricated by combining the cladding shaping with the thermal core expansion techniques by using a CO2-laser LZM-100 glass-processing system. The experimental results show a side-mode suppression ratio (SMSR) of 49 dB and a linewidth of 0.06 nm, within the range from 1038 to 1080 nm. In conclusion, the main achievement of this switchable laser is the high SMSR and stable output for high values of temperature, using a repeatable, simple, easy construction, and cost-effective laser tuning technique.