| 摘要 |
A tunable semiconductor laser comprises a propagation region in which a waveform can exist, the propagation region comprising sequential gain and control regions, the gain region comprising a light amplification region supplied by a source of excitation, and the control region comprising a periodic structure through which the waveform propagates. The control region can be linked to a source of current thereby to enable changes to be made to the refractive index thereof. It is preferred that the material of the propagation region is (Ga,In)(N,As). As a result, in the gain region the waveform will be less tightly confined and hence a higher gain can be produced without suffering from saturation of the gain material. Ideally, there will be tight confinement of the waveform in the control region to allow maximum advantage to be made of the change in refractive index. This can be achieved by controlling the physical configuration of the control region, such as by forming the propagation region with a lesser transverse width in the control region, and/or including non-semiconducting regions to confine the waveform. One way of achieving the latter is to include Al-containing layers in the propagation region; these can be oxidised to produce Al2O3.
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