486nm blue laser operating at 500 kHz pulse repetition frequency

Abstract

Compact, high power blue light in the 470-490nm region is difficult to generate due to the lack of laser sources which are easily convertible (through parametric processes) to those wavelengths. By using a pulsed Tm-doped fiber laser as a pump source for a 2-stage second harmonic generation (SHG) scheme, we have generated ~2W of 486.5nm light at 500kHz pulse repetition frequency (PRF). To our knowledge, this is the highest PRF and output power achieved in the blue region based on a frequency converted, monolithic fiber laser. This pump laser is a pulsed Tm-doped fiber laser/amplifier which generates 12.8W of 1946nm power at 500kHz PRF with diffraction-limited output from a purely single-mode fiber. The output from this laser is converted to 973nm through second harmonic generation (SHG). The 973nm is then converted to 486.5nm via another SHG stage. This architecture operates with very low peak power, which can be challenging from a nonlinear conversion standpoint. However, the low peak power enables the use of a single-mode monolithic fiber amplifier without undergoing nonlinear effects in the fiber. This also eliminates the need for novel fiber designs, large-mode area fiber, or free-space coupling to rod-type amplifiers, improving reliability and robustness of the laser source. Higher power and conversion efficiency are possible through the addition of Tm-doped fiber amplification stages as well as optimization of the nonlinear conversion process and nonlinear materials. In this paper, we discuss the laser layout, results, and challenges with generating blue light using a low peak power approach.

High-power 1560 nm single-frequency erbium fiber amplifier core-pumped at 1480 nm

“…Then, large-mode area EYDFs, which can raise the SBS threshold and moderate thermal accumulation, are used to generate a high-power SF laser at 1.5 μm. In 2016, Creeden et al [ 14 ] reported a 207 W 1560 nm SF fiber amplifier with a measured M 2 of 1.05 using EYDF of a core/cladding diameter of 25/300 μm, which to our knowledge is the highest power SF laser at 1.5 μm up to now. Although the M 2 of less than 1.1 is good for the majority of applications, it still corresponds to higher order modes content of up to 30% [ 15 ] .…”

Nonlinear chirped pulse amplification for a 100-W-class GHz femtosecond all-fiber laser system at 1.5 m

“…The slope efficiency of the main fiber amplifier is about 36.28%, and 23.21% and 25.38% for the third and fourth pre-amplifiers, respectively. It should be pointed out that although the EYDF has a lower pump absorption at 940 nm (typically, four times lower than that of 974 nm) that may lead to a larger length of gain fiber, the use of a 940-nm pumping strategy can effectively reduce the thermal effect [ 42 ] and suppress the amplified spontaneous emission (ASE) [ 43 ] . The autocorrelation trace, as shown in Figure 5(b), exhibits a pulsewidth of 293 fs, assuming a sech 2 -pulse shape.…”

Highly efficient frequency doubling and quadrupling of a short-pulsed thulium fiber laser

“…In this paper, we investigate the frequency doubling of a picosecond (ps) Tm-doped fiber laser and demonstrate a conversion efficiency as high as 75% which is, to the best of our knowledge, the highest efficiency yet for a frequency-doubled Tm-doped fiber laser. Furthermore, we explored the frequency quadrupling of the ps Tm-doped fiber laser to generate blue light for potential applications such as data storage, displays and spectroscopy [13]. An output power of 690 mW is obtained at a wavelength of 488 nm.…”