Fiber Optic Tutorials

This is a continuation from the previous tutorial - vertical-cavity surface-emitting lasers (VCSELs).   1. Background Information Optical amplifier, as the name implies, is a device that amplifies an input optical signal. The amplification factor or gain can be higher than 1,000 (>30 dB) in some devices. There are two principal types of optical amplifier: the semiconductor-laser amplifier (SLA), and the fiber amplifier. In an SLA, light is amplified when it propagates through a semiconductor medium fabricated in the form of a waveguide. In a fiber amplifier, light is amplified when it travels through a fiber doped with rare-earth ions...

This is a continuation from the previous tutorial - quantum well semiconductor lasers.   1. Background Information Semiconductor lasers described in the previous tutorials have cleaned facets that form the optical cavity. The facets are perpendicular to the surface of the wafer and light is emitted parallel to the surface of the wafer. For many applications requiring a two-dimensional laser array or monolithic integration of lasers with electronic components (e.g., optical interconnects), it is desirable to have the laser output normal to the surface of the wafer. Such lasers are known as surface-emitting lasers (SEL). There is a class of...

This is a continuation from the previous tutorial - diverse applications of coupled-cavity semiconductor lasers.   1. Energy Levels A double-heterostructure laser consists of an active layer sandwiched between two higher-gap cladding layers. The active-layer thickness is typically in the range of 0.1-0.3 μm. In recent years, double-heterostructure lasers with an active-layer thickness of ~ 10 nm have been fabricated. The carrier (electron or hole) motion normal to the active layer in these structures is restricted. As a result, the kinetic energy of the carriers moving in that direction is quantized into discrete energy levels similar to the well-known quantum-mechanical problem...

This is a continuation from the previous tutorial - operating characteristics of coupled-cavity semiconductor lasers.   In the operating characteristics of coupled-cavity semiconductor lasers tutorial the performance of coupled-cavity semiconductor lasers was discussed from the standpoint of their applications in optical fiber communications as a single-frequency optical source. However, such lasers exhibit features that are useful for many other applications as well. This is particular true for active-active three-terminal devices, and many interesting applications of these have already been proposed an demonstrated. In this tutorial we briefly describe some of the diverse applications of \(\text{C}^3\) lasers.   Optical Bistability The...

This is a continuation from the previous tutorial - coupled-cavity semiconductor lasers.   In this tutorial we present the experimental results for coupled-cavity lasers with particular attention paid to active-active \(\text{C}^3\) devices. The properties considered are longitudinal-mode selectivity under CW operation, wavelength tuning with current adjustment, domains of single-mode operation under modulation, and the frequency chirp. A few transmission experiments employing \(\text{C}^3\) lasers are also briefly described. Finally, we discuss the performance of external-cavity semiconductor lasers and their potential applications in optical fiber communications.   1. Longitudinal-Mode Control Figure 8-8 shows an example of the \(L-I\) curves obtained at room...