| 摘要 |
<p>A laser comprising a quantum cascade layer structure, said quantum cascade layer structure comprising n repeating periods of a plurality of layers, wherein n is an integer of at least 2, said plurality of layers being configured to primarily support a plurality of discrete energy states, adjacent periods being separated by a barrier layer, the laser being configured such that electrons, injected into an m<th> plurality of layers in a m<th> period, descend through at least one energy state of said m<th> plurality of layers into an energy state of a m+1<th> plurality of layers in an m+1<th> period, and an overlap condition (formula (I)) is satisfied, where m is an integer between 2 and n, Psi 2,m+1 is the normalised wave function in nm of a second state of the m+1<th> period, Psi 1,m is the normalised wave function in nm of a first state of the m<th> period and x is measured from the injection barrier which lies between the m<th> and m+1<th> periods, measured in the direction towards the m<th> period, the second state of the m+1<th> period is the state of the m+1<th> period which is closest in energy to the ground state of the m<th> period, the ground state of the m<th> period being defined as the state which has the largest amplitude of the states on the m+1<th> side of the barrier layer, and the first state of the m<th> period being defined as the state which forms the largest dipole within a period with the second state, wherein the dipole can be expressed mathematically as: (formula (II)).</p> |
