三输出功率与能量. In section 4.1 we derived an expression for thethreshold population inversion at which the lasergain becomes equal to the losses. We wouldexpect that as the pumping intensity is increasedbeyond the point at which N,-N,=N, the laserwill break into oscillation and emit power. In thissection we obtain the expression relating thelaser power output to the pumping intensity. Wealso treat the problem of optimum coupling-thatis, of the mirror transmission that results in themaximum power output
三 输出功率与能量 • In section 4.1 we derived an expression for the threshold population inversion at which the laser gain becomes equal to the losses. We would expect that as the pumping intensity is increased beyond the point at which N2 -N1 =Nt the laser will break into oscillation and emit power. In this section we obtain the expression relating the laser power output to the pumping intensity. We also treat the problem of optimum coupling-that is, of the mirror transmission that results in the maximum power output
·激光器稳态工作的建立·连续或长脉冲激光器的输出功率(output power)·短脉冲激光器的输出能量(output energy)
• 激光器稳态工作的建立 • 连续或长脉冲激光器的输出功率 (output power) • 短脉冲激光器的输出能量(output energy)
In chapter 3 we found that an atomic mediumwith an inverted population (N,>N) is capableof amplifying an electromagnetic wave if thelatter's frequency falls within the transitionlineshape. Consider next the case in which thelaser medium is placed inside an opticalresonator
• In chapter 3 we found that an atomic medium with an inverted population (N2>N1 ) is capable of amplifying an electromagnetic wave if the latter’s frequency falls within the transition lineshape. Consider next the case in which the laser medium is placed inside an optical resonator
: As the electromagnetic wave bounces back andforth between the two reflectors it passed troughthe laser medium and is amplified. If theamplification exceeds the losses caused byimperfect reflection in the mirrors and scatteringin the laser medium, the energy stored in theresonator will increase with time. This causesthe amplification constant to decrease as a resultof gain saturation
• As the electromagnetic wave bounces back and forth between the two reflectors it passed trough the laser medium and is amplified. If the amplification exceeds the losses caused by imperfect reflection in the mirrors and scattering in the laser medium, the energy stored in the resonator will increase with time. This causes the amplification constant to decrease as a result of gain saturation
: The oscillation level will keep increasing untilthe saturated gain per pass just equals thelosses. At this point the net gain per pass isunity and no further increase in the radiationintensity is possible-that is, steady stateoscillation obtains
• The oscillation level will keep increasing until the saturated gain per pass just equals the losses. At this point the net gain per pass is unity and no further increase in the radiation intensity is possible-that is, steady state oscillation obtains