Influence of energy-transfer upconversion on the performance of high-power diode-end-pumped CW lasers

Abstract

The influence of energy-transfer upconversion (ETU) on the performance of diode-end-pumped lasers is studied by including ETU effects into the space-dependent rate equations. The dependence of ETU rates on the mode-to-pump size ratio and on the output mirror transmission is derived. Experiments for Nd : YAG and Nd : YVO 4 crystals are performed to validate the present model. It is found that the ETU process increases the sensitivity of the output power to the output mirror transmission but its influence on the output power is not significant for low output transmission.

Modeling of high-power continuous-wave Tm:YAG side-pumped double-clad waveguide lasers

“…Our experimental observation that we were unable to obtain lasing with a 50% output coupler is, therefore, attributed to the presence of upconversion. Similar effects due to energy-transfer upconversion have also recently been described in CW -doped lasers [13]. The main reason for the drop in output power at low reflectivity for the case where no upconversion is present is depletion of the ground state, leading to a smaller absorption efficiency.…”

Stokes and anti‐Stokes blue light emissions of thermal‐evaporated silica sub‐micron wires

“…On the basis of analysis above, it is suggested that the emission from ODCs might be caused by multistep energy transfer from NBOHCs to ODCs, the schematic of which is shown in Fig. 3c, thus the possible upconversion mechanism for anti‐Stokes emission above is interpreted to be energy transfer 24–26.…”

Diode-end-pumped continuous wave single-longitudinal-mode Nd:GdVO4laser at 1342 nm

“…For a single transverse mode and an ideal four-level Nd-doped laser, we can write the rate equation of population densities in the upper laser level N (r, z) and the total laser photons number in the cavity Φ in the steady state as [12,14] dNr; z dt…”

“…A number of papers have shown that the influence of energy-transfer upconversion (ETU) may be a detrimental effect in Nd-doped lasers [8][9][10][11][12][13][14][15][16][17][18][19][20]. The ETU process involves two nearby ions in the 4 F 3∕2 upper laser level; one ion relaxes down to a lower-lying level and transfers its energy to the other ion, which thereby upconverts to a higher level.…”