Optical sciences are the central theme of the 2014 Nobel Prizes in both Physics and Chemistry. The prizes were announced on 7 and 8 October respectively. Two Nobel Prizes were announced on two consecutive days, to novel technologies, both based on optical sciences. Isamu Akasaki and Hiroshi Amano at Nagoya University, Japan, and Shuji Nakamura of the University of California at Santa Barbara have won the Nobel Prize in Physics for the invention of blue light-emitting diodes (LED, an energy-efficient and environment-friendly light source).
The prize citation honours the trio for “the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”. LEDs are used in numerous devices such as the very familiar blinking lights in computers and mobile phones. As if one Nobel Prize in optical sciences for 2014 was not enough, the Nobel Prize for Chemistry was awarded to Eric Betzig (USA), Stefan W. Hell (Germany) and William E. Moerner (USA) “for the development of super-resolved fluorescence microscopy”. The traditional optical microscopy has strict limitations to the highest magnification it can offer (based on some laws in optics). The award winners were able to develop a new type of microscopy, which enables to see objects far beyond the reach of the traditional optical microscopes.
It is to be recalled that in December 2013, the United Nations proclaimed 2015 as the International Year of Light and Light-based Technologies (see the article, in Radiance Viewsweekly, Vol. LI, No. 40, pp. 21-22, January 5-11, 2014). It is a very remarkable coincidence that both the Physics and Chemistry Nobel Prizes for 2014 have been awarded to light sciences. This is a tremendous boost to the year-long celebrations of light that will highlight to the citizens of the world the importance of light and optical technologies in their lives, for their futures, and for the development of society.
In the context of human vision, the three basic or primary colours are red, green and blue. These can be combined to produce a wide range of colours. The white light is made of red, blue and green. In other situations the primary colours can be different. For instance, in colour printing the primaries normally used are cyan, magenta, and yellow; for painters the primaries are generally red, yellow and blue.
In the familiar light bulbs, the light comes from a heated filament and the heating is done by electric current. Most of the electrical energy is consumed in producing heat. LEDs produce light by an entirely different mechanism (movement of electrons in a special semiconductor material). LEDs are energy efficient and have a much longer life than the light bulbs. LEDs have been around since the 1950s and emitted red and green light. Over the years the efficiency and the applications of the LEDs grew but the much needed blue LED could not be produced for three decades. The much awaited blue LED was created in 1993 after decades of research and development. Entirely new class semiconductor materials had to be created using new physics and the tailor made technologies.
We need the white light to illuminate the world around us. With the blue LED there are two distinct ways to produce white light lamps. A lamp made from red, blue and green LEDs collectively produces white light. Alternately, blue LED light acting on certain special materials called phosphor produces green and red light, which combines with the blue to produce white light. Both the methods are in use today. The blue LEDs have revolutionised the field of illumination technology. Compared to the light bulbs, the LED lamps consume less energy and last much longer. It is to be noted that about a quarter of the electricity is consumed for lighting. So, a wide-spread usage of LED lamps will save a lot of power worldwide. LED Lamps are more suited to work on solar power.
The optical microscopes have been around since the 17th century (or even earlier). They were used for studying the living organisms giving birth to the field of microbiology. Optical microscopes are the basic tools used by biologists. They are also used in medical laboratories to examine the blood and other tissues. Since the beginning there were efforts to improve the resolution of the microscope, that is to distinguish smaller and smaller objects.
In the meantime, scientists working in optical sciences were coming up with new results to understand the nature of light. This contributed to the development of new optical instruments and the improvement of existing ones including the microscopes. But there was one result which heavily disappointed all the users of microscope: the optical microscope had a natural limitation of 0.2 microns (one micron is a thousandth of a millimetre) on the resolution. In practice what it means that the optical microscope is good to see the cells but not the inner structure of the cells. The viruses and molecules are still smaller. This calculation was done by Ernst Abbe (1873) and Lord Rayleigh (1896) and is part of the regular college curriculum. Other microscopy methods (developed in the 20th century), such as electron microscopy, require preparatory measures that eventually kill the cell.
For many decades, it was thought that optical microscopy is bound by 0.2 micron resolution. Abbe’s equation is still valid for the traditional optical microscope which uses the ordinary white light for illuminating the sample and seeing the magnified image.
A new type of microscopy called fluorescence microscopy works on an entirely different principle, and does not violate the Abbe’s limit. The fluorescence microscope is based on the phenomenon that certain materials emit energy detectable as visible light when the light of a specific wavelength (colour) shines on them. Fluorescence microscopy has a much higher resolution. Fluorescence microscopy developed by the three Nobel laureates is being used worldwide. It has been used to study the movement of proteins within the tiny cells; tracked cell division inside embryos; look closely at the nerve cells. Such studies are bound to have a deep impact on our understanding of medicine and diseases at a cellular and molecular level.
[SAMEEN AHMED KHAN is on the Engineering Department, Salalah College of Technology (SCOT), Salalah, Oman. [email protected]]