What is “Photonics” and why do we need it?
The term ‘Photonics’ appeared first in the late 1960s and gradually became a unique throughout late 20th century. From the name, this much can be guessed that it has something to do with ‘Electronics’ but where photons are involved. Actually, photonics is a unique field comprising technology, modern devices and research to make use of light in the functions that traditionally fall under electronics. Long story short, it uses photons instead of electrons. The applications are numerous but it can be defined as the practical science of generation, detection and manipulation of photons and use them for information processing, signal processing, modulation, computing, signal amplification etc.
Photons are particles like electrons but they are of bosonic type which means they are massless and have full integer spin. They are the smallest entity that form light. Although, light is made of countless photons, it has dual characters, wave and particles.
In photonics, not the light but the photon particles are used. The photons are controlled and manipulated to do various kinds of things. They are generated and harnessed in a controlled environment. Although photonic applications use all sorts of radiant energies that are formed by photons but the most used are visible and near-infrared photons in the electromagnetic spectrum. The desired photons are generated by stimulated emission. So, LASERs form the basic device requirements for photonics. In LASER, photons are created by stimulated emission. Photons are pumped to a metastable layer and forced to go to an upper level that causes the population inversion. When they are released to go to a lower level, stimulated emission occurs. A cavity resonator is used which keeps the beam in a desired coherence and frequency. So, in photonic applications, LASERs are the basic devices to generate photons. Then some other arrangements are used to bring the photonic signal to a desired outcome. Mainly, semiconductor-based light sources are used in generating light. Beside LASERs, LEDs and superluminescent diodes are also used.
As mentioned above, the applications of photonics are numerous. In everyday life, we use photonic principles. The simplest and known of them can be X-Ray photography, lighting, telecommunications etc. Optical fibers that revolutionized the world of communications use photonic principles. Photonics is the science that created the basic structure of the ‘Internet’. Like electronics, photonic applications have been rising dramatically since the invention of LASER.
Amplification and modulation are two another important applications that now are done with optical signals. They were previously owned by electronics only. Light modulation is done to encode information in the signal. They can be done with light source directly which was not possible with electrons. Also, they can be efficiently modulated by optical modulators. The simplest of light modulation can be thought as using a flashlight to send Morse code.
Light amplification is done by optical amplifiers that include fiber amplifiers, semiconductor amplifiers, Raman amplifiers and parametric amplifiers. The amplified signal is much more efficient than an electronic one.
Light detection is already done by photodiodes. Other devices include charge coupled devices (CCD) that work in a medium speed and solar cells that are extremely slow in detecting photons and thus amplifying them which is used in harvesting energy from sunlight. CCDs are used in digital cameras.
The newly emerging devices are photonic integrated circuits (PICs) that include a wide array of applications. The circuits have two main parts, a gain medium and a mirror with desired grating like in a LASER. They are used in data centers, analog RF signal applications, sensors and a new kind of image processing named light imaging, detection and ranging (LIDAR) which enable a sort of 3D imaging of light signals which gives a certain level of precision in information processing. This enables a machine to measure and process certain data and use to ensure the users’ needs. This new form of machine vision is already being used in various applications like driverless cars.
After all the applications of photonics, the question still arises “Why do we need it?” To start, we need photonics because it replaces electrons in the field of modern devices. Electrons are also particles but they are Fermions, which means they have mass and half-integer spin. The mass of electrons create a problem. The electrons can’t get a super speed even if they want to. That will violate the law of physics. But photons are massless. They are thus super-speedy. The photons promise higher bandwidth than electrons.
A report of US National Resources and Defense Council in 2013 calculated that the data centers of the tech companies in America alone consumed 34 large 500-MW coal-fired power plants which is now approximately doubled. This enormous data traffic is if handled with the photonic integrated circuits which will enable the greater Tbit/s rate with half as much power dramatically reducing the cost.
The photonic devices’ enormous bandwidth are advantageous to the end users without increasing their significant costs. This is due to the exotic properties of photonic devices. Moreover, the PICs’s GHz precision information processing can manipulate RF signals with high fidelity and send the signals over a long range of distance. The PICs are also more efficient in filtering noise from information.
This is a very promising field. Also, it will gain more applications and the technology will be more efficient when Si photonics and quantum dot research are successful which will mark the majestic emergence of Quantum Computing.
