Visible-Light Laser Diodes and Superluminescent Diodes: Characteristics and Applications

Semiconductor light-emitting technology has seen tremendous strides in recent decades and a rapidly increasing interest in it. The unique advantages and characteristics of this form of light generation include compactness, high efficiency, and reliability. With these recent advancements, light-emitting diodes (LEDs), laser diodes, and superluminescent diodes (SLDs) have become an indispensable part of our homes, factories, and research facilities. In particular, the sensitivity of the human eye to the visible wavelengths of the electromagnetic spectrum extending from 400 to 700 nm, and the optical response of many materials to such spectrum, make visible light indispensable for a plethora of applications ranging from displays for entertainment, to imaging in the medical field, to light-based atomic clocks. While LEDs are the most commonly found type of semiconductor light sources, laser diodes and SLDs are of special interest due to their higher output optical power, spectral purity, and coherence. In this tutorial, we first go over the main unique characteristics of the different types and configurations of visible-light laser diodes and SLDs and their general structures with a focus on their advantages compared to LEDs. We then discuss the applications in which these characteristics are of great interest in the fields of displays, communication, instrumentation, and photonic integrated circuits.