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The term quantum defect is ambiguous. Various meanings are discussed below. Characteristic is that the defect deals with the loss on the smallest energy scale of light: that of the quantum. ==Quantum defect in laser science== In laser science, the term quantum defect refers to the fact that the energy of a pump photon is generally higher than that of a ''signal photon'' (photon of the output radiation). The difference of energies goes to the heat; this heat may carry away the excess of entropy delivered with the multimode uncoherent pump. The quantum defect of a laser can be defined as part of the energy of the pumping photon, which is lost (not turned into photons at the lasing wavelength) in the gain medium at the lasing. At given frequency of pump and given frequency of lasing, the quantum defect . Such quantum defect has dimension of energy; for the efficient operation, the temperature of the gain medium (measured in units of energy) should be small compared to the quantum defect. At a fixed pump frequency, the higher the quantum defect, the lower is the upper bound for the power efficiency. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「quantum defect」の詳細全文を読む スポンサード リンク
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