東南大學(xué)考研固態(tài)電子器件20xx-20xxcha-資料下載頁(yè)
2025-08-11 16:05本頁(yè)面
【正文】 ??)()()/()/(/1222122112112221???? nBnAnBdtdndtdndtdns t a t es t ea d yf o rstsp????)(/)()。(/)(。/)(12121112122122212221????BndtdnWBndtdnWndtdnAststsp????? A21: spontaneous emission probability。 W21 ： stimulated emission probability。 W12： stimulated absorption probability A21,B21 and B12 are called Einstein coefficients optical resonant cavity (FabryPerot)法布里 珀羅共振腔 ) )()( 12212122112221 ????ABnAnBr a t ess p ont aneour a t ee m i s s i ons t i m ul at e d ??The way to enhance the stimulated emission is to have a very large photon field energy density ?(?12) : an optical resonant cavity in which the photon density can build up to a large value through multiple internal reflections at certain frequencies(?12 ). 2?m?LHow to build up? There must be the medium in the cavity to provide the gain. population inversion(分布反轉(zhuǎn) ) 1122211211212221)()(nBnBnBnBr a t ea b s o r p t i o nr a t ee m i s s i o ns t i m u l a t e d??????If stimulated emission is to dominate over absorption of photons from the radiation field, we must have a way of maintaining more electrons in the upper level than in the lower level, that is n2n1. How to maintain n2n1? Pump!! ?Gain Medium ?Optical Resonant Cavity ?Pum
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