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Optical Electronics, Fall 2022 Laser characteristics ? spectrally broad ? divergent ? can’t be focused tightly ? not very intense ? incoherent ? very monochromatic ? does not diverge as fast ? can be focused tightly ? can be extremely intense ? spatial coherence (interference) ? temporally coherent (beat notes) What is needed ? More generally: ? gain medium ? pump far from thermal equilibrium ? feedback (resonator, mirrors, cavity) 發(fā)散 非相干 單色 干涉 反饋(諧振器,鏡子,腔) :光束的選擇性 增益物質(zhì)(激活物質(zhì)) :?jiǎn)喂? 泵浦源(激勵(lì)源) :粒子數(shù)反轉(zhuǎn) Optical Electronics, Fall 2022 1897年發(fā)明法布里 — 珀羅空腔諧振器 20世紀(jì) 50年代中期,肖洛與美國著名物理學(xué)家湯斯共同研究微波激射問題。 當(dāng)湯斯提出受激輻射放大原理時(shí),肖洛第一個(gè)提出運(yùn)用沒有側(cè)壁的 開放式法 布里 珀羅腔作振蕩器 的設(shè)想。 1960年,他和湯斯研制出 第一臺(tái)激光器 。 FabryPerot Etalon Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 增益飽和,粒子數(shù)不再反轉(zhuǎn)的時(shí)候 Gain? 當(dāng)受激輻射超過受激吸收和自發(fā)輻射的時(shí)候,即粒子數(shù)發(fā)生反轉(zhuǎn) 固體(氣體、液體)增益物質(zhì):三能級(jí),四能級(jí) 半導(dǎo)體增益物質(zhì):直接帶隙,間接帶隙 Optical Electronics, Fall 2022 Loss:損耗 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 簡(jiǎn)稱開腔,全稱:開放式光學(xué)諧振腔 共軸球面腔:穩(wěn)定腔、不穩(wěn)腔、臨界腔, Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 *不同分子、原子及半導(dǎo)體材料中的電子有不同的 Δ E,其中半導(dǎo)體材料的 Δ E可變范圍很大 Optical Electronics, Fall 2022 Optical Electronics, Fall 2022 Diffe