Large-mode-area (LMA) photonic crystal fiber (PCF) amplifiers are attractive for high-power amplification of single-mode (SM) narrow-linewidth light. Traditionally, LMA PCF designs include air holes but splicing and interfacing of fibers with air holes is complicated. Recently, this was addressed with the development of a LMA PCF amplifier fiber without air holes but with SM operation maintained. This all-solid fiber can be spliced with standard splicers and thus enables integration of PCFs into all-fiber monolithic laser systems. The new fiber, named DC-250/30-PM-Yb-FUD, is demonstrated in a free-space configuration for high-power amplification of 1064 nm light with a narrow linewidth of less than 20 kHz. A seed power of 380 mW is amplified to 40 W, corresponding to a single-stage gain of 20 dB, with an optical to optical efficiency of 69%. No indication of stimulated Brillouin scattering is observed, and the output is stable during frequency modulation of the seed laser.
In this work, an all-solid Ytterbium doped double-clad single-mode (SM) large-mode-area (LMA) photonic crystal fiber (PCF) is characterized in a monolithic amplifier setup. The characterized all-solid PCF combines the SM operation of LMA PCFs while maintaining simple splicing of all-solid fibers. The fiber has been tested in a pulsed monolithic forward pumped amplifier system achieving excellent modal properties. The fiber is polarization maintaining and has a mode field diameter of approximately 24 μm. At optimal fiber length the output signal power of the amplifier was measured to 43 W limited by pump power with an optical to optical efficiency of 61 %. Polarization extinction ratios (PER) above 18 dB was observed for all fiber lengths. Simple splicing with splice losses < 0.2 dB and maintained polarization are reported using a standard Fujikura fusion splicer.
Photonic crystal fiber (PCF) technology has radically impacted the scientific and industrial ultrafast laser market. Reducing platform dimensions are important to decrease cost and footprint while maintaining high optical efficiency. We present our recent work on short 85 μm core ROD-type fiber amplifiers that maintain single-mode performance and excellent beam quality. Robust long-term performance at 100 W average power and 250 kW peak power in 20 ps pulses at 1030 nm wavelength is presented, exceeding 500 h with stable performance in terms of both polarization and power. In addition, we present our recent results on hollow-core ultrafast fiber delivery maintaining high beam quality and polarization purity.
Photonic crystal fiber (PCF) technology for ultrafast fiber amplifiers traditionally uses air holes as key elements for large mode area (LMA) fiber designs. These air holes are crucial for the performance of high-end LMA PCFs, but makes splicing and interfacing more complex. To reduce this complexity in mid-range amplifiers, we present single-mode polarization-maintaining Yb-doped LMA PCFs without air holes for easier splicing into monolithic all-fiber amplifier designs. <p> </p>A 30 μm core all-solid spliceable PCF is presented, and amplification of 1064 nm light above 50 W with an optical to optical efficiency of 80 % is demonstrated.<p> </p> Furthermore, to demonstrate the excellent reliability of PCF based monolithic amplifiers, we demonstrate ultra-longterm performance data of > 35 khrs on a 14 μm core step-index type PCF amplifier with low long-term power degradation slope of < 1.5 % / 10,000 h.