High-efficiency hybrid brillouin/ytterbium fiber laser

Abstract

A high-efficiency hybrid Brillouin/ytterbium fiber laser (BYFL) is demonstrated using a 41.5-cm-long highly ytterbium-doped fiber and a 10-m-long single-mode optical fiber. The BYFL operates at 1 052.92 nm, and the difference between it and the Brillouin pump (BP) wavelength matches the expected stimulated Brillouin scattering (SBS) Stokes shift. Its output power reaches 70.1 mW, which is more than seven times higher than the seeded BP power. The BYFL has an optical signal-to-noise ratio that is greater than 65 dB and has many potential applications, such as in controllable optical delay lines, sensing, and RF photonics.OCIS , optical carrier amplitude control [3] , gyroscopes [4] , and lasers [5] . Brillouin fiber lasers (BFLs) have attracted significant interest for decades due to their linewidth narrowing effect. The free-running spectral linewidth of the singlefrequency Brillouin ring fiber laser has been reported to be only a few hertz [6] , which can be several orders of magnitude narrower than that of their single-frequency pump beams. Moreover, the BFL exhibits low relative intensity and frequency noises. All these advantages make the BFL applicable in controllable optical delay lines, sensing [7] , and radio frequency (RF) photonics [8] . For a conventional ring-cavity Brillouin laser, the pump-coupling ratio depends on the cavity loss and the round-trip phase shift in the cavity, which must be an integer number of 2π to achieve the intensity enhancement. Although the conventional BFL exhibits useful characteristics, it has disadvantages such as the small output power, the requirement of cavity matching to the pump signal, and the difficulty in incorporating intracavity elements because of their associated loss. The hybrid Brillouin/ytterbium fiber laser (BYFL) can overcome these disadvantages by using an ytterbium-doped fiber amplifier to compensate for the resonator losses while still commencing a lasing action from the Brillouin gain.A high-efficiency BYFL based on Ref.[9] is demonstrated in this letter. When the Brillouin pump (BP) power is 9.68 mW, the laser output power reaches 70.1 mW at a 980-nm pump power of 383 mW, compared with that of Guan's work, which obtains only 40 mW of laser output. This BYFL has an optical signal-to-noise ratio (OSNR) that is greater than 65 dB. Figure 1 shows the BYFL configuration. The BP, a distributed feedback laser diode with a linewidth of less than 70 kHz at 1 052.86 nm, was amplified by a fiber amplifier and then seeded into the laser cavity through a circulator and a 70/30 coupler. The BP was first amplified by a 41.5-cm-long highly ytterbium-doped fiber (HYDF) with a pump absorption rate of 975 dB/m. Then, the BP entered into a 10-m-long single-mode fiber (SMF), which functions as the Brillouin gain medium. The Stokes wave was generated in the SMF and circulated clockwise, and a 1 053-nm isolator was inserted in the cavity to prevent the laser from injection locking to the BP. The 70/30 coupler coupled the laser out of the cavity through the 70% port, wherea...

325 MHz and near transform-limited pulse output directly from an Er:fiber ring laser

“…Nonlinear polarization evolution (NPE) [10] relies on a rapid saturation absorption mechanism and takes advantage of very short pulse generation. Unfortunately, NPE is only applicable to ring lasers [11] , which limits the achievable frequency spacing.…”