We demonstrate a pulsed Er-doped ZBLAN fiber laser at 3750 nm based on the gain-switching scheme. A diffraction grating was introduced as a wavelength selection component to enable stable lasing in this long-wavelength region, which has deviated from the emission peak of 4F9/2→ 4I9/2 transition in Er3+. Different from the convention gain-switching behavior where the Pulse Repetition Frequency (PRF) of output laser is same as the that of the pump, three switchable gain-switched temporal states with 1/n (n=4,3,2) pump PRF rates are observed in experiment. The pulse evolution, including average output power, PRF, pulse duration, and peak power, in response to the 1950 nm pump power are investigated in detail. Over 200 mW average output power at 3750 nm was obtained under 12 W of 1950 nm pump power. The pulse repetition frequency, pulse energy and pulse duration were 35.4 kHz, 6.7 μJ and 1.2 μs, respectively. This work represents the longest pulsed emission wavelength generated from rare-earth doped fiber lasers.
In this work, we demonstrated that a single pump source in the 1.57-1.72 μm band can enable mid-infrared 2.8 μm lasing in Er-doped fluoride fiber via ground state absorption and excited-state absorption. The efficiency evolution of 2.8-μm fiber lasers with respect to pump wavelength was experimentally investigated. The high slope efficiency of ⪆50% and low laser threshold of ⪅0.1 W have been achieved with optimized fiber doping concentration and pump wavelength. This pioneer work paves the way for the further power scaling of mid-infrared 3 μm Er fiber lasers pumped by near-infrared fiber lasers.
The efficient Nd:YVO4/KGW Continuous-Wave (CW) intracavity Raman lasers in linear and folded cavities were demonstrated. The coupled cavity scheme was utilized to control the beam sizes in the laser crystal and Raman crystal, to alleviate the thermal issues and enhance the Raman gain. With the 1064 nm fundamental laser polarized along Nm axis of the Np-cut KGW crystal, 6.63 W of linear cavity and 9.33 W of folded cavity Stokes output at 1177.3 nm were obtained under an incident laser diode pump power of 36.65 W, with an optical efficiency of 18.1% and 25.5%, respectively. Our results show that the compact intracavity Raman laser is capable of generating multi-watt CW output efficiently by proper cavity arrangement. 10-watt level Raman output can be realized in the V-shaped cavity through parameter design. In contrast, the folded cavity scheme is more favorable for higher Stokes output power as well as efficiency compared with the linear cavity scheme because of its better mode matching.
In this work, the effect of 2 μm core pump wavelength on the quenching behavior of 3.5 μm Er-doped ZBLAN fiber laser are experimentally investigated in detail. Pumped at an optimized wavelength of 1990 nm, a maximum 3.47 μm output power of approximately 7.2 W was obtained with 6.5 m Er-doped ZBLAN fiber, where the slope efficiency (with respect of launched 1990 nm pump power) and overall optical efficiency are 36% and 26.5%, respectively. Numerical simulation was implemented to reproduce the experimental results and determine the cross section of ESA via a theoretical fitting.
A single-frequency Tm-doped fiber laser operating at 2050 nm is demonstrated with a ring cavity scheme. A piece of unpumped Tm/Ho-coped fiber saturable absorber incorporating a high reflectivity fiber Bragg grating, which serves as a narrow bandwidth filter, were inserted inside the cavity to select single longitudinal mode and suppress the mode hopping. By optimizing the length of Tm/Ho-codoped fiber, stable single-frequency lasing at 2050 nm was realized. Under 2 W 1570 nm pump power, 215 mW single-frequency output power was obtained, while the slope efficiency with respect to the launched pump power was 22%. This work shows that using Tm/Ho-codoped fiber or Ho-doped fiber as the saturable absorber, which has a higher absorption above 2 μm, could enhance the mode selection capability thus improve the singlefrequency output power.
High-power single-frequency fiber lasers have attracted great attention in the applications of high-resolution spectroscopy, long-distance coherent communication, gravitational wave detection and some other areas, due to the advantage on narrow linewidth, low noise and so on. In this paper, we systematically summarize the recent achievements of high-power singlefrequency fiber laser oscillators and amplifiers as well as performance improvement on noise suppression, linewidth narrowing, and wavelength extension. Besides, the next development of SFFLs has been prospected.
We propose and demonstrate a novel method to achieve pulsed operation of thulium-doped fiber lasers at 1.7 μm. In our design, the thulium-doped fiber laser cavity was embedded within the cavity of an erbium/ytterbium-codoped fiber laser operating at 1.5 μm. The thulium-doped fiber in the erbium/ytterbium-codoped fiber laser cavity served as a saturable absorber, forcing the 1.5 μm laser to operate in a passively Q-switched scheme. The 1.7 μm thulium-doped fiber laser was in-turn pumped by the Q-switched 1.5 μm laser and was gain-switched. This resulted in the pulse duration of 1.7 μm emission was much shorter than that of 1.5 μm emission. 1.02 W average output power at 1720 nm was obtained for 10 W of pump power at 976 nm. The pulse repetition frequency, pulse energy and pulse duration were 134 kHz, 7.6 μJ and 102 ns, respectively.
Saturable absorption effect of unpumped active fiber can be used as a method of achieving single-frequency operation from an all-fiber oscillator. Here, the effect was studied when the signal was highly absorbed by unpumped thulium-doped fiber and the laser threshold was beyond the available pump power. We proved that the oscillator could be manipulated to the “oscillating state” by injecting auxiliary pump light to the saturable absorber fiber. This allowed using unpumped thulium-doped fiber with higher absorption to enhance the frequency selecting capability. A record single-frequency output power of 2.56 W at 1720 nm was obtained, with a slope efficiency of 44% and a linewidth of 3.3 kHz, the power scaling of which was only limited by the available power of the single-mode 1570 nm pump source. This work offers new insights into how high-power, single-frequency fiber oscillators can be produced.
We have demonstrated an efficient 1720-nm all-fiber laser with ring-cavity configuration based on commercial Tmdoped silica fiber and 1570-nm in-band pump source. The rate equation model was built up to analyze the laser performance of Tm-doped fiber, which exhibits strong absorption in 1.7-μm region. The results show that efficient laser operation can be achieved through the optimization of output coupling and the length of Tm-doped fiber. By using homemade couplers, we experimentally achieved 2.36-W laser output power under 6-W launched pump power. The slope efficiency with respect to the absorbed pump power and optical efficiency were 50.2% and 39.3%, respectively. Due to the employment of ring resonator, a narrow laser linewidth of ~4 GHz at maximum output power was observed.
We observed a large optical bistability in a single-frequency thulium fiber laser with ring cavity configuration. A piece of unpumped Tm-doped fiber served as nonlinear saturable absorber (SA), which also acted as a narrow-bandpass filter by forming self-induced gratings with counter-propagate lasers and enabled single-frequency laser operation at 1720 nm. Due to the large absorption cross section of thulium ions at 1720 nm, the unpumped Tm-doped fiber has large variable losses, hence resulting in strong optical bistability. With 0.75-m SA fiber, a 4.8-W wide bistable region was achieved. The evolution of bistable region with different lengths of SA fibers was investigated. The bistable region became narrower with decreasing SA fiber length, and totally disappeared at a SA fiber length of 0.15 m. To the best of our knowledge, this is the first observation of optical bistability in thulium fiber lasers.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.