M.L. Sundheimer

Characterization of efficient dual-wavelength (1050 + 800 nm) pumping scheme for thulium-doped fiber amplifiers

We report on the characterization of a recently introduced dual-wavelength pumping scheme for thulium-doped fiber amplifiers using 800 and 1050 nm. Using a counterpropagating pump configuration, 180 mW of total pump power yielded 27-dB small-signal gain and less than 5-dB noise figure. Furthermore, using optical frequency domain reflectometry, the distributed gain in this configuration was evaluated, allowing for optimization of the doped fiber length.

Optimization of spectrally flat and broadband single-pump fiber optic parametric amplifiers

Abstract Using well-known theory for fiber optical parametric amplifiers in the no-depletion approximation, a simple condition relating the second- and fourth-order dispersion parameters β 2 and β 4 is demonstrated which ensures ripple-free, broadband gain spectra using realistic fiber parameters. Inclusion of pump depletion gives rise to expressions which enable optimization of fiber length and the maximum achievable ripple-free gain.

Dual-wavelength (1050 nm +1550 nm) pumped thulium-doped fiber amplifier characterization by optical frequency-domain reflectometry

We present experimental results of distributed gain measurements from a dual-pumped (1050 nm +1550 nm) thulium-doped fiber amplifier using optical frequency-domain reflectometry. We show that significant reductions in total pump power and/or fiber length are realized with the addition of a few milliwatts at 1550 nm. For our experimental conditions, the addition of 5 mW of 1550 nm allows for a reduction of 100 mW of pump power at 1050 nm or a reduction of 44% of doped fiber length to reach the same gain as with 1050-nm pumping alone.

Ferroelectric domain inversion in congruent lithium niobate

We present results of ferroelectric domain inversion studies in congruent lithium niobate which clarify some important aspects of the dynamics of the process such as the alignment of the internal electric field, initiation of poling, switching time, conditions for spontaneous backswitching and stabilization of inverted domains, and the influence of the impedance of the poling apparatus. These results are of practical interest for designing poling processes for the fabrication of periodically-poled lithium niobate.

Black box model for thulium doped fiber amplifiers

We present and experimentally validate a black box model for TDFAs. The gain at any wavelength is predicted from measurements of three spectral functions and the gain at two reference wavelengths.

Low pump power, short-fiber dual-pumped (800 nm+1050 nm) TDFA

A 5-m long 2000-ppm Tm-doped fiber pumped with 145-mW total at 800 nm+1050 nm wavelengths produced 18-dB gain. Optical frequency domain reflectometry revealed the gain distribution and permitted optimizing the system.

The Internal Electric Field and Backswitching in Congruent Lithium Niobate

We present experimental results showing the correlation between the internal electric field and the backswitching phenomenon in congruent lithium niobate. The large internal electric field, responsible for the offset of the hysteresis loop, is shown to have reoriented parallel to the new spontaneous polarization after two months at room temperature and is shown not to be the cause of backswitching. The reduction and recovery of the poling field after a backswitching event are presented, showing that the coercive field for the domains that were involved in the backswitching is significantly reduced, recovering to its nominal value after approximately 200 ms. These results indicate the presence of a fast component to the internal electric field which decays with a time constant of 50 ms. The dependence of backswitching on the impedance of the poling circuit is also shown.

Comparison of distributed gain in 800 nm+1050 nm or 800 nm+1410 nm pumping schemes for thulium-doped fiber amplifiers using optical frequency domain reflectometry

Distributed gain in thulium-doped fiber amplifiers using 800 nm+1050 nm or 800 nm+1410 nm pumps was studied. We show that the former is advantageous over the later primarily due to ground state absorption.