Measuring the lasing threshold of a passively Q-switched diode-pumped pulsed solid-state laser

Pulse interval jitter of a diode-pumped solid-state laser with instantaneous Q-switching of the resonator

“…(12). For β = 10 −15 , the times τ inY and τ inC for the YAG:Nd and CGGG:Nd lasers [13], which are determined by the quantum fluctuations of spontaneous emission, are 15 and 31 ns, respectively, which is higher than the pulse interval jitter of the diode-pumped solid-state laser considered in [16] by three orders of magnitude. The latter circumstance shows the necessity to allow for the influence of the quantum fluctuations of spontaneous emission on the laser pulse-interval stability during the laser-parameter optimization.…”

“…For the CGGG:Nd laser [13], similar quantities are equal to n C = 2.0 · 10 20 cm −3 , τ C = 220 μs, σ C = 1.4 · 10 −19 cm 2 , and d C = 1.5 mm, respectively. The effective diameter D of the mode in an active element is the same and equals 90 μm for both lasers [13]. For n a = 1.5, q = 1, β = 10 −5 [11], and the inverted population density n i , which is equal to the neodymium-ion concentration, we obtain τ inY = 1.5 · 10 −13 s and τ inC = 3.1 · 10 −13 s. The 586 obtained values for τ inY and τ inC are smaller than the typical values of pulse interval jitter for the YAG:Nd and CGGG:Nd lasers [14] by several orders and seem to be the lowest possible jitter for these devices.…”

“…Let us estimate this time for lasers on neodymium-activated crystals of yttrium aluminum garnet (YAG:Nd) and calcium gallium germanium garnet (CGGG:Nd) [13]. For the YAG:Nd laser [13], the neodymium-ion concentration n Y = 0.8 · 10 20 cm −3 , the radiation lifetime of the upper laser level is equal to τ Y = 230 μs, the effective cross section of the induced transitions σ Y = 3.2 · 10 −19 cm 2 , and the active-element thickness d Y = 4.1 mm. For the CGGG:Nd laser [13], similar quantities are equal to n C = 2.0 · 10 20 cm −3 , τ C = 220 μs, σ C = 1.4 · 10 −19 cm 2 , and d C = 1.5 mm, respectively.…”

“…For the YAG:Nd laser [13], the neodymium-ion concentration n Y = 0.8 · 10 20 cm −3 , the radiation lifetime of the upper laser level is equal to τ Y = 230 μs, the effective cross section of the induced transitions σ Y = 3.2 · 10 −19 cm 2 , and the active-element thickness d Y = 4.1 mm. For the CGGG:Nd laser [13], similar quantities are equal to n C = 2.0 · 10 20 cm −3 , τ C = 220 μs, σ C = 1.4 · 10 −19 cm 2 , and d C = 1.5 mm, respectively. The effective diameter D of the mode in an active element is the same and equals 90 μm for both lasers [13].…”

“…Approximate analytical expressions (13) and (14), which are obtained within the framework of the above analysis, simplify estimation and optimization of the laser parameters in order to reduce the pulse intervals jitter. To improve the accuracy of the results, one should use the quantum-electrodynamic approach [17,18].…”