Hundred-hertz Single-frequency Fiber Lasers

Lasers with a linewidth of <1kHz can find various applications in optical atomic clocks,high-resolution laser spectroscopy, measurements of fundamental constants, and tests offundamental physics. Short-linear-cavity (SLC) single-frequency fiber lasers are consideredto be a promising candidate for the above-mentioned applications due to its narrow linewidthsand compact sizes. However, the laser linewidth of a free-running SLC fiber laser everreported is typically a few kilo hertz. Complicated techniques were employed to suppress thelaser linewidth to less than1kHz.After a theoretical analysis of the elements that deteriorate laser linewidth, weintroduced a method to extend the intra-cavity life time by using the delay of fiber-Bragg-grating F-P filter. And we introduced the twisted-mode technique for the elimination ofspatial hole burning effect. Laser linewidth measurement with loss-compensated recirculatingdelay self-heterodyne detection method was also discussed in Chapter2.In Chapter3, it was experimentally testified that virtual-folded-ring single-frequency(VFR-SF) fiber laser operated in single-mode condition under thermal controlled. Theeffective cavity length was2times of the physical length of the oscillator. Laser output with alinewidth of820Hz was obtained with the reduction of spatial hole burning effect.In Chapter4, we studied the characteristic of the slow-light single-frequency (SL-SF)fiber laser. The photon lifetime was extended due to the slow light effect of the filter. Thelinewidth of the output of the SL-SF fiber laser was measured to be around780Hz. Weobserved dual-wavelength lasing during the experiment of the SL-SF fiber laser. We modifiedthe structure of the cavity and achieve simultaneous dual-wavelength lasing. Microwavesignals centered at~12GHz with <3kHz linewidth were demonstrate with the heterodynedetection of the dual-wavelength single-longitudinal-mode fiber laser. Later, by perfecting theexperimental setup, a switchable microwave signal output centered at~15GHz,~22GHz and~25GHz with <10kHz linewidth was obtained.In Chapter5, slow-light virtual-folded-ring single-frequency (SL-VFR-SF) fiber laser was proposed and demonstrated. The SL-VFR-SF fiber laser had both the advantages broughtby slow light effect and the reduction of SHB effect. The linewidth of the output of theSL-VFR-SF fiber laser was measured to be around600Hz.