Smartphone technology is getting better and cheaper with each passing day. People have developed interesting apps and technologies smartly using the hardware. The smartphone app industry is projected to be at least $77 billion industry by the end of 2017 (1). This burgeoning market has greatly influenced and instigated a sense of competition among other industries as well. The development of Smart TV’s can serve as a good example to how versatile and useful modern day smartphones have become (2).
Diffraction has been considered historically as a nuisance for the optics enthusiast, from Galileo to the designers of the Hubble telescope. Refractive and reflective optics have been used as the de facto tools in the optical designer’s toolbox for centuries, along with accurate modeling techniques using light as a particle such as Snell’s law of refraction. But light has a dual nature and can be also considered as a wave, which opens new design and modeling windows based on diffraction of light rather than refraction.
Diffractive and Holographic optical elements (respectively DOEs and HOEs) are used today in numerous consumer electronic devices such as CD/DVD reader heads, gesture sensors such as Kinect for Xbox, anti-counterfeiting tags, and even in augmented reality (AR) headsets such as Hololens.
The industry sector has also been embracing the use of diffractive optics such as in CWDM Mux/Demux for optical telecom, dispersion gratings in spectroscopy or high resolution optical encoders for motion control applications.
By structuring a substrate directly at the micrometric or even nanometric scale, through Integrated Circuits (IC) manufacturing process such as optical lithography and dry etching, one can produce very interesting diffractive elements. The picture below is an Atomic Force Microscope (AFM) scan of typical diffractive micro-structures. The lateral dimension of the AFM scan below is 10 microns.
If you play a guitar string, you will hear a note, whose tone will depend on the string diameter and on the string tension. This sound is not just made of a pure (“single”) vibration, which would sound rather ugly and boring, but rather to the overlap of several acoustic frequencies playing simultaneously, which makes the note “round” and pleasant. More than that: it makes the note unique. You will be able, in fact, to tell it’s a guitar and not a piano, or even which kind of guitar. The very same concept applies to the voice of people: you can easily distinguish two persons pronouncing the same sentence at the phone because they have a different tone. The ensemble of the vibrating frequencies that form the sound and the voice is called the timbre. In physics, we call it spectrum, and it not only applies to sound but also to light, indicating its various frequency components, i.e. its colors!
Supernova explosions are one of the most powerful events in the known universe—the violent death of a star. They radiate tremendous energy, outshine entire galaxies, and release elements that make up our physical bodies. Supernovas are also an important birthplace for primordial, “grandparent”, magnetic fields that played a crucial role in the formation of large-scale objects such as our own galaxy. However, the origin of these fields is one of the greatest mysteries facing contemporary astronomers.
Ultrafast, high-power lasers produce very short pulses, as short as one tenth of one millionth of one million of a second. At the speed of light, this time corresponds to the thickness of a hair! Due to this very short duration, these lasers concentrate their energy into a very high power, that allow very spectacular applications.
Among these applications, one can mention the influence of lasers on high-voltage discharges. Recently, it was shown that an adequate choice of the light phase across the laser beam (known as «Airy beams») allow to generate curved self-guided filaments of light . Furthermore, these curved light filaments can self-heal if they hit an obstacle. They are also ionized, hence electrically conducting. Based on these properties, researchers from several groups around the world demonstrated the possibility to guide discharges over a curved path, and to circumvent an obstacle, as shown in the picture below .