Laser Light Amplification by Stimulated Emission of Radiation

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???????(Laser) Light Amplification by
Stimulated Emission of Radiation
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???????????????? (Emission)
?????????????????????????? (Spontaneous
Emission) ????????????????????????????????????????
???????????????????????????????????????????????
E2 -E1 ??????????????????????????????????????????
???????
E2
E1
Spontaneous Emission
??????????????????????????????????? (Stimulated
Emission) ?????????????????????????????
??????????????????????????????? E2 -E1
?????????????????????? ??????????????????????????
??????????????????????????????? E2 -E1
?????????????????????????????????
???????????????????? ??????
E2
E1
Stimulated Emission
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Lasers
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????????????????
If a medium has many excited molecules, one
photon can become many. Stimulated emission leads
to a chain reaction and laser emission.
Excited medium
This is the essence of the laser. The factor by
which an input beam is amplified by a medium is
called the gain and is represented by G.
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??????????????
Laser medium
1. ??????????????(Active medium ) --gt
??????????? ???? ?????(dye) ????
????????????,.. ?????
Population inversion
2. ?????????????????(Energy source) --gt
???????????????????????? ???? ?????? ????
????????? ???? ?????.

• 3. ?????????? (Resonator) --gt ????????????????????
  100 ??????????????? lt100

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L
Laser medium
M1
M2
Energy pump

• ?????????????????????????????????
  ?????????????????????????????????
• ??????????????????????????????
• ????????????????????????????????????????normal
  mode ???????????????
• ??????????????????????stimulated emission
  ?????????????????????????????-??
• ??????????????????????????????????????????????????
  ????????????????????
• ???????????????????????????????????????-??????????
  ? ??????? Steady state

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Ruby Laser
?????? ???????????
??????????
???????? ?????????????
???????? ?????? 100
????? ?????????
???????
???????
Spontaneous Emission
Power source
???????????????????????????????
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He-Ne Laser
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Laser Diode

• F.B. ???? pn junction ?????????? e ??? hole ??
  recombine ???? ???
• ????? 2 ?????????? L ????????????????????????-??
  ???? Fabry-Perot ??? 2 ??????????????????????????
  ??????????????? ????????????????? resonance
  modes ????????????????????????????????

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