Output-coupling optimization of Nd-doped fiber lasers

Design of rare-earth-doped microbottle lasers

Coupling strength in taper-coupled microbottle resonators can be tuned by offsetting the taper along the resonator profile, similar to controlling the air-gap in microsphere excitation, and hence, achieve desired coupling characteristics for a specific mode. Such flexibility makes microbottles attractive and adaptable laser cavities. In this paper, lasing characteristics of Yb³⁺-doped microbottle laser (MBL) coupled to tapered fiber are theoretically investigated. It is demonstrated that desired lasing characteristics for a particular mode are achievable by controlling the taper-resonator coupling, intrinsic quality factor (Q) and dopant concentration. Although, high Q whispering gallery cavities provide high internal powers, which is favorable especially for low gain materials, they lack high output powers. Hence, care should be taken in designing MBLs to attain the highest possible output power. Here, we address such issues, and optimized the required resonator parameters (for both pump and signal) for a low threshold pump power, high efficiency and desired lasing wavelength.

Investigation on the effect of output mirror transmission in WS2-based red-light passively Q-switched Pr:ZBLAN all-fiber lasers

We report the experimental investigation of visible passively Q-switched Pr³⁺-doped all-fiber lasers with tungsten disulfide (WS₂) saturable absorber, where red-light short-pulse generations from different output mirror transmissions are systemically characterized. The proposed simple and compact all-fiber linear cavity was constructed by a fiber-pigtail-based blue laser-diode pump, a Pr³⁺-doped fluorozirconate glass active fiber, and the fiber end-facet mirrors. Integrating a free-standing layered WS₂ film into the laser cavity initiated the Q-switching operation. Stable microsecond-duration output pulses with kilohertz repetition rates are achieved, corresponding to a few mW/nJ average output power and single-pulse energy. The comparisons on red-light Q-switched output parameters for output transmissions of both ∼40% and ∼80% are performed. This work could provide a useful guideline to manipulate the output performance of visible pulsed all-fiber lasers for various practical applications.

1.6 μm emission based on linear loss control in a Er:Yb doped double-clad fiber laser

Based on the control of the linear losses of the cavity, we demonstrate the possibility to achieve filterless laser emission above 1.6 μm, from a C-band double-clad Er:Yb doped fiber amplifier. The concept is validated in both continuous wave and mode-locked regimes, using a figure-of-eight geometry. A unidirectional ring cavity is also tested in the continuous regime. Spectral properties of laser emissions are characterized as a function of the intracavity linear losses.

Dual-wavelength continuous-wave cascade oscillation at 3 and 2 mum with a holmium-doped fluoride-glass fiber laser

We have demonstrated dual-wavelength continuous-wave oscillation at 3 and 2 mum with a Ho-doped ZrF(4)- BaF(2)- LaF(3)- AlF(3)- NaF fluoride-glass fiber laser by use of a cascade oscillation scheme. We have shown that the fiber laser operates with a high slope efficiency of 52% (at 3 and 2microm) with respect to the absorbed pump power. With a 6.5-m-long fiber we achieved an output power of 90 mW at each of the wavelengths that was limited only by the pump power, and the 3-microm output power is to our knowledge higher than any previously reported level with 3-mum Ho(3+) -doped fiber lasers.