Watt-level ultrahigh-optical signal-to-noise ratio single-longitudinal-mode tunable Brillouin fiber laser

Abstract

A watt-level ultrahigh optical signal-to-noise ratio (OSNR) single-longitudinal-mode (SLM) tunable Brillouin fiber laser (BFL) has been demonstrated. By optimizing the length of the single mode fiber (SMF) cavity at 11m and its output ratio at sixty percent, 1.04 W output power, as well as stable SLM operation is obtained at 2.24 W pump power. The single pass cavity BFL has the advantage that Brillouin pump frequency doesn't need to match the cavity mode, thus the stability is greatly improved. As only SMF is used in the cavity, the operate wavelength can be tunable without the restriction from self lasing cavity mode. Furthermore, it proves that core-pumped single frequency fiber laser is able to generate watt-level power. The laser has excellent performance in terms of noise, linewidth, and stability. © 2012 Optical Society of America OCIS code: 060.3510, 140.3510, 190.2640. High power single-longitudinal-mode (SLM) fiber lasers with high optical signal-to-noise ratio (OSNR) have enormous applications such as remote sensing, ladar, coherent detection, and nonlinear optics. Recently, the output power of fiber lasers grew quickly, but SLM fiber lasers did not [1]. SLM fiber lasers can be boosted to watt-level [2,3], but it is still a challenge to preserve high OSNR. Besides, the output power of SLM fiber laser is also limited by the backward stimulated Brillouin scattering (SBS) [3,4]. Owing to narrow band gain of SBS, Brillouin fiber lasers (BFLs) with ~10m cavity can operate at SLM status. Though the threshold of BFLs [5] can be reduced to submilliwatt level, but the pump frequency has to match the cavity mode. This causes a big trouble for practical operation owing to the inevitable fluctuation of pump frequency. Moreover, it is difficult to output large power as the cavity is critically coupled [5]. Hybrid BFLs including active media don't need the critically coupled resonator [6], and they are able to achieve large power. A 1 W SLM Brillouin/ytterbium fiber laser with 60 dB OSNR has been demonstrated [7]. However, for a hybrid BFL, the wavelength tunability is limited at the self-lasing range [8]. Besides, it inevitably introduces amplified spontaneous emission (ASE) noise from active fibers. Different than hybrid BFLs, the BFLs without active fibers have wider tunable range, higher OSNR, and narrower linewidth. A SLM BFL with 12 m length cavity has been reported and shown stable output power [9]. In this letter, only SMF is used in the single pass cavity. By exploiting the high efficiency of SBS in fibers and the large output ratio of the lasing cavity, we demonstrate a wattlevel SLM tunable BFL with 75dB OSNR.Figure1 shows the configuration of the BFL, which consists of a tunable laser source (TLS) with 100 kHz linewidth, an erbium-doped fiber amplifier (EDFA), a polarization controller (PC), an optical circulator (OC) with 20% power loss, a 60/40 coupler with 5% loss. The cavity length is 11 m, corresponding to 18 MHz free spectral range. The laser from TLS is amplified by the EDFA as the input Brill...

Inducing and harnessing stimulated Brillouin scattering in photonic integrated circuits

“…Brillouin amplifiers with low noise figures ∼4 dB [103,104], however, have been reported in slow-light demonstrations. Brillouin lasers, which use the generator configuration, have also been reported with large signal-to-noise ratio of ∼75 dB [105]. Therefore, by choosing appropriate pump and signal power and cavity configuration, good signal-to-noise ratio can be obtained for the SBS.…”

Single Longitudinal Mode Brillouin Fiber Laser With Cascaded Ring Fabry–Pérot Resonator

“…In the BFL, suppose that pump and SBS are polarized along the same direction, the threshold input power P th is inversely proportional to the effective cavity length L eff = [1 − exp(−2αL t )]/2α . P th is given by [7], [13] R exp(g P th L ef f /A − αL t ) = 1…”

“…Circulator based single ring cavity has the advantage that the Brillouin pump frequency does not need to match the cavity mode. On the other hand, when the cavity mode spacing of about 10 m or 20 m cavity length [7]- [13] is comparable to the Brillouin gain, the BFL easily operates in SLM (single longitudinal mode) status. However, because of length limitation of SLM operation, it is difficult to improve the threshold power and linewidth.…”

A Novel Technique for Designing High Power Semiconductor Optical Amplifier (SOA)-Based Tunable Fiber Compound-Ring Lasers Using Low Power Optical Components

“…The power fluctuations during the stability measurement can be minimized by properly packaging the proposed fiber compound-ring laser system. The obtained OSNR spectrum is in the range that is comparable to the OSNR levels for fiber lasers used in remote sensing [69,70], fiber sensors that utilize wavelength-peak measurement method [62] and optical communication systems [71].…”