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OPTICS LETTERS / Vol. 36, No. 18 / September 15, 2011
400 mW ultrashort cavity low-noise single-frequency Yb3 -doped phosphate fiber laser Shanhui Xu, Zhongmin Yang,* Weinan Zhang, Xiaoming Wei, Qi Qian, Dongdan Chen, Qinyuan Zhang, Shaoxiong Shen, Mingying Peng, and Jianrong Qiu State Key Laboratory of Luminescent Materials and Devices and Institute of Optical Communication Materials, South China University of Technology, Guangzhou 510640, China *Corresponding author:
[email protected] Received June 23, 2011; revised August 22, 2011; accepted August 22, 2011; posted August 24, 2011 (Doc. ID 149805); published September 15, 2011 A compact, low-noise, single-frequency fiber laser by using a newly developed Yb3þ heavily doped single-mode phosphate glass fiber has been demonstrated. Over 400 mW stable continuous wave single transverse and longitudinal mode laser at 1:06 μm was achieved from a 0:8 cm long active fiber. The measured slope efficiency and estimated quantum efficiency of laser emission are 72.7% and 93%, respectively. The signal-to-noise ratio is higher than 72 dB, and the linewidth of the fiber laser is less than 7 kHz, while the measured relative intensity noise is less than −130 dB=Hz at frequencies of over 1:5 MHz. © 2011 Optical Society of America OCIS codes: 140.3510, 060.2280, 140.3615.
A single-frequency fiber laser at 1:06 μm has experienced intense research in the past few years for applications, such as laser interferometric gravitational-wave observatory, advanced remote sensing, coherent beam combining, kilowatt-class high power laser with a master oscillator power amplifier technique, and laser LIDAR [1–4]. Especially in the application of multiple paths coherent beam combining, a low-noise single-frequency laser with hundreds of milliwatt output power is required. Although optical amplifiers can boost the singlefrequency output power, it is still preferable to obtain the hundreds milliwatt level, high signal-to-noise ratio laser directly from fiber oscillators. A short linear resonance cavity configuration, such as a distributed Bragg reflector (DBR), is beneficial to single-frequency laser emission for mode-hop-free, narrower linewidth, lower noise, and all in a compact all-fiber design [5–7]. Y. Kaneda et al. have reported a DBR laser at 1:06 μm with >200 mW output power in a Yb3þ -doped phosphate glass fiber for first time [8]. A single-frequency laser with the linewidth of 72 dB
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Intensity (arb. units)
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1064nm fiber laser Slope efficiency: 72.7%
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power of 570 mW, which is the highest output power from this kind of fiber lasers reported to date [8,15–17]. The slope efficiency against the launched pump power is measured to be 72.7%, and the experimental quantum efficiency of the laser emission related to the absorbed pump power is estimated to be 93%, since only 85% of the pump power was coupled into the phosphate fiber core due to the coupling loss, scattering, and pump leakage. From our understanding, these are also the highest slope efficiency and quantum efficiency from this kind of single-frequency fiber laser [8,15–17]. The stabilities of the output power at 300 mW in an hour were investigated and the result is shown in Fig. 2(d). The power instability of
