P2O5-doped Fiber Research Articles

Active Compensation of Differential Group Delay in a Dual-Wavelength Pulsed Fiber Laser Driven by Quasi-Synchronous Pumping

We report on synchronized dual-wavelength (1.07 μm and 1.24 μm) pulsed lasing driven by a quasi-synchronous primary pumping (at 0.98 μm) of an Yb-doped fiber laser, which incorporates also a P2O5-doped fiber as an intracavity Raman converter. The original method developed for such lasing does not require saturable absorbers (or optical modulators) and dispersion management. We demonstrated that the mechanism of the quasi-synchronous pumping enables the aforesaid stationary lasing in spite of significant differential group delay (DGD) inevitably acquired by light pulses with such different wavelengths during an intracavity round trip due to large normal chromatic dispersion. This DGD can be actively compensated at every round trip by the forced “acceleration” of the pulses at 1.07 μm in the Yb-doped active fiber due to the overrated frequency of the quasi-synchronous pumping at 0.98 μm. This mechanism is related to the particular pulse amplification dynamics in a such gain-modulated active fiber. The demonstrated approach to synchronized dual-wavelength pulsed lasing in a single-cavity fiber laser features remarkable simplicity and reliability. Our proof-of-concept setup enabled the stable two-wavelength generation of regular trains of nanosecond pulses with energy up to 34 nJ at equal repetition rates.

Acoustic coefficients of P_2O_5-doped silica fiber: the strain-optic and strain-acoustic coefficients

We present measurements and modeling of the effect of P2O5 doping on the strain sensitivity coefficients of silica fibers. In particular, the Brillouin gain spectrum of a heavily P2O5-doped fiber is measured and investigated at different strains. We provide measurements of the strain-optic coefficient (SOC) and the strain-acoustic coefficient (SAC), obtained to be + 0.139 and + 9854m/sec/e, respectively, both of which are less than the pure silica values. The Pockels’ coefficients p11 and p12 for bulk P2O5 are also estimated via Brillouin gain measurements. Using the strain coefficients, the modeled and unique slopes of the Stokes’-shift-versus-strain curves for the four observed acoustic modes in the fiber each lie within 2% of the measured values.

Characterization of an Intra-Cavity Pumped P2O5-Doped Silica Raman Fiber Laser

We examine the characteristics of a P2O5-doped Raman fiber laser pumped by a double-clad ytterbium-doped fiber laser in an intra-cavity configuration. The double-clad fiber laser consists of two high reflection fiber Bragg gratings at 1092 nm, with an active length of 17 m, where the output grating is located at the end of the 400m P2O5-doped fiber. The Raman cavity is formed by a 1278-nm-high reflection fiber Bragg grating spliced to the double-clad fiber, and a 50% output coupler. The maximum conversion efficiency at 1278 nm with respect to the input pump power at 915 nm was 26.9%.

Numerical Modeling and Experimental Confirmation of an Efficient Phosphosilicate-Fiber Raman Laser

A model for a fiber Raman laser has been numerically solved including all the interactions between forward and backward travelling waves. The predicted numerical results are experimentally confirmed using a fiber Raman laser with P2O5-doped fiber. The maximum output power of 3.1 W at 1483.5 nm with a slope efficiency of 46% is experimentally obtained using a 300 m P2O5-doped fiber. Numerical results suggest that an output power of as much as 4 W with a slope efficiency of 57% can be achieved if the Raman cavity is optimized for the same input pump power.

Output characteristics of a fibre Raman laser with a composite GeO2 and P2O5-doped silica fibre

A new type of fibre Raman laser composed of a GeO2- and P2O5-doped silica fibre was investigated experimentally and theoretically. The output of the laser displays two difference characteristics depending on the type of fibre being used as the input end. Using the P2O5-doped fibre as the input end, the Raman Stokes line of 1320cm−1 shift was enhanced by the latter GeO2-doped fibre. While the GeO2-doped fibre used as the input end, a wideband continuous spectrum was obtained. A model including effects of bandwidth of the Raman gain, four-wave mixing and the mutual influence of the GeO2- and P2O5-doped silica fibre was constructed to illustrate the experimental observation.