激光二极管是一种激光产生器，其工作物质是半导体，属于固体激光产生器，大部份激光二极管在结讲上与一般二极管相似。由于激光二极管的运作中，电子的能量转变过程只涉及两个能阶，没有间接带隙造成的能量损失，所以效率相对高。能发光的半导体电子组件，透过三价与五价元素所组成的复合光源。此种电子组件早在1962年出现，早期只能够发出低光度的红光，被惠普买下专利后当作指示灯利用。及后发展出其他单色光的版本，时至今日，能够发出的光已经遍及可见光、红外线及紫外线，光度亦提高到相当高的程度。用途由初时的指示灯及显示板等；随著白光发光二极管的出现，近年逐渐发展至被普遍用作照明用途。

A laser diode, or LD, is an electrically pumped semiconductor laser in which the active laser medium is formed by a p-n junction of a semiconductor diode similar to that found in a light-emitting diode.

The laser diode is the most common type of laser produced with a wide range of uses that include fiber optic communications, barcode readers, laser pointers, CD/DVD/Blu-ray Disc reading and recording, laser printing, laser scanning and increasingly directional lighting sources.