Photonics

What is the difference between optics and photonics?

Optics is a general area of physics covering a wide range of topics related to the study of light. Optics includes such subfields as geometrical optics, physical optics, and quantum optics. Photonics is a subset of the optics discipline. 

Geometrical optics, sometimes referred to as classical optics, is primarily concerned with the manipulation of light using devices such as lenses, mirrors and prisms. In geometrical optics, light is modeled using the ray approximation. In the ray approximation, light wavefronts are approximated as a collection of rays, each perpendicular to the wavefront of light and representing the energy flow through the system. A typical application of geometrical optics would be the design of an imaging lens for a camera. 

Physical optics is the study of light where the wave nature is predominant. In physical optics the ray approximation is not valid since interference and diffraction effects must be accounted for. Physical optics tends not to include effects caused by the particle nature of light. A typical application of physical optics would be the production of holographic images.

Quantum optics is the study of light phenomena where the particle, or quantum, nature of light is important. Quantum optics and photonics are closely related, but quantum optics tends to be more theoretical and photonics is more concerned with the design of practical applications. A typical area of study for quantum optics would be theoretical study of the physics of light creation at the p-n junction inside an LED. 

Why is photonics important to us today?

We are at the beginning of a photonics revolution. Photonic devices have become ubiquitous in everyday life but often go unnoticed. Light sources such as LEDs and laser diodes have found their way into countless applications where light must be created. These devices are relatively cheap, extremely lightweight and compact, and are quite rugged with a long usable life span. In addition, these solid-state sources generate less heat and require less power compared with more traditional light sources. LEDs are being deployed widely as a replacement source technology due to their significant energy and replacement cost savings.

Photonics represent a growing opportunity for designing and manufacturing devices, systems and integrated circuits for applications in high-speed data communications, advanced sensing, and imaging. Photonic technologies promise orders-of-magnitude speed improvements with reduced power consumption for data transmission and ultrasensitive sensing capabilities in multiple domains.

Photonic-based detectors such as CMOS image sensors (CIS) have transformed how we take photographs and have all but replaced film as a media for capturing images. CIS share some of the same benefits as solid state sources in that they are small, rugged, and lightweight. One of the biggest advantages over traditional film is their light sensitivity and compact size. This allows for much smaller optics to create a usable image on the detector. This has enabled compact, high-quality cameras being added to everything from cell phones to automobiles.

By combining sources and detectors with other means of manipulating light, photonics engineers have transformed our digital world with fiber optic communications, scanners, medical devices, agricultural advances and a whole host of other applications.

What are some real-world photonic applications?

Photonics devices effect a very wide range of applications. Telecommunications is heavily dependent on photonics devices for fiber optic networks that greatly increase the capacity and speed of internet communications all the way down to the home. Lighting has been transformed with the advent of affordable, powerful LEDs that cut power consumption while providing high-quality, flexible lighting solutions. Solid-state lasers are now commonly found in applications from medical to industrial. Light weight, compact light sensors are found in devices as diverse as cellphone cameras, bar code scanners, printers, DVD players and automotive sensors. Finally, the emerging field of photonic computing is working towards the goal of supplementing or replacing traditional electronic-based printed circuit boards and integrated circuits with optoelectronic circuits.

What does a photonics engineer do?

Photonics engineers design photonics devices, circuits, and systems used for a wide range of applications. The complexity of photonic design problems require photonics engineers to have a thorough understanding of quantum and physical optics and often geometrical optics. The work is both creative and demanding. Photonics engineers must keep up with the latest research and techniques as well as maintain a good familiarity with the limits of manufacturability.

Effective design of photonics devices requires the use of specialized software tools used in the modeling of the behavior of light. The photonics engineer uses these tools to build virtual prototypes of the system under design and then uses the simulation tools built into the software to analyze the behavior of light as it interacts with the device. The engineer then optimizes the design to achieve the desired performance in a buildable package.