High optical gain in erbium-doped potassium double tungstate channel waveguide amplifiers

Abstract

Abstract:We report on the optical-gain properties of channel waveguides patterned into lattice-matched KGd x Lu y Er 1-x-y (WO 4 ) 2 layers grown onto undoped KY(WO 4 ) 2 substrates by liquid phase epitaxy. A systematic investigation of gain is performed for five different Er 3+ concentrations in the range of 0.75 to 10at.% and different pump powers and signal wavelengths. In pump-probe-beam experiments, relative internal gain, i.e., signal enhancement minus absorption loss of light propagating in the channel waveguide, is experimentally demonstrated, with a maximum value of 12 ± 5 dB/cm for signals at the peakemission wavelength of 1534.7 nm.

Energy-transfer upconversion and excited-state absorption in KGdxLuyEr1-x-y(WO4)2 waveguide amplifiers

“…The branching ratios, in which we consider fast multiphonon-relaxation processes 4 F 9/2 → 4 I 9/2 → 4 I 11/2 in the intermediate levels, are calculated from the electric-dipole radiative-transition rate constants, radiative lifetimes, and branching ratios given in [29] cm −3 ( = 6.3at.%), a maximum gain of ∼15 dB/cm is calculated, slightly depending on the assumed value of the propagation loss. The simulation overestimates the experimentally achieved gain of ∼12 dB/cm [47] by approximately 25%, which may be due to (i) a non-negligible influence of the ETU 2 and CR processes, (ii) errors in the approximation of the relevant parameter values, and most likely (iii) heating of the waveguide when pumping in the experiment, which leads to a temperature increase and, consequently, a reduction of transitions cross sections. This reduction, which leads to line broadening, is a fundamental process in rare-earth ions.…”

“…(a) Simulated internal net gain per unit length (equalling the stimulated-emission coefficient γ minus the propagation loss coefficient α loss ) versus Er 3+ concentration in potassium double tungstate channel waveguides at the peak gain wavelength for three different propagation losses (lines). Comparison with experimental results (data points) from [47]. (b) Simulated internal gain assuming a high propagation loss (α loss = 4 dB/cm), including ESA and ETU (black continuous line), excluding ESA and including ETU (red dashed line), and including ESA and excluding ETU (blue dotted line).…”

Erbium-doped hybrid waveguide amplifiers with net optical gain on a fully industrial 300 mm silicon nitride photonic platform

“…Yet, the erbium-doping can be increased up to a certain limit as the high erbium-incorporation introduces unwanted transitions and quenching of active ions within the gain medium, which ultimately lead to diminishing returns in the amplifier performance. To optimize the performance of erbium-based integrated amplifier devices, various host materials and different fabrication methods have been studied to achieve high erbium-incorporation inside different compounds [7][8][9][10][11][12][13][14][15][16][17][18][19]. Additionally, unique waveguide geometries have also been proposed to maximize the interaction of the guided beams with the active layer [20][21][22][23][24][25].…”

Erbium-doped polymer waveguide amplifiers for PCB-integrated optical links

“…It has been identified however, that for such devices much higher ion concentrations are needed due their desired much shorter lengths than EDFAs, on the order of a few centimetres for practical applications [14]. As a result, in order to reach the required erbium concentrations with minimal ion clustering and gain quenching a number of fabrication techniques have been employed, such as atomic layer deposition [15], liquid phase epitaxy [16] or RF-sputtering [17] with some good results. Out of these, ultra-fast laser plasma implantation (ULPI) appears to be most promising [18].…”