new green and blue laser sources

The lighting technology in our kitchen comes from Nichia LEDs. It required quite a bit of research, because the main light source in the kitchen is a large skylight oriented to south-east. Therefore, to work in the twilight of dawn and dusk, we needed both high efficiency in terms a luminance and a smooth spectrum compatible with D illuminants.

Recently, Nichia has developed laser technology that could make LCD televisions 25% more energy efficient than LED-based TVs. The major maker of LEDs has created a way to produce laser light that is 1,000 times stronger than laser light created through conventional methods, but which uses less power.

The company implemented semiconductor design changes that made it possible to create a laser system capable of emitting stronger blue and green light. The semiconductor device is made of gallium nitride, the same material used in LEDs. Green and blue laser light has traditionally been relatively weak and therefore is not used in many commercially available products.

Unlike light created by LEDs, laser light does not get diffused and thus can illuminate liquid crystal display TVs and PC monitors with far less power when used as backlighting — up to 50% in the case of PCs. Mitsubishi Electric and other companies have already developed red semiconductor lasers that can emit a strong light, but until now there had been no such system for green and blue lasers.

Nichia's breakthrough means semiconductor laser light is now available in the three primary colors. Nichia has begun shipping samples to consumer electronics makers and aims to commercialize the technology by 2016.

Source: Nikkei

non-locality

Researchers at the University of Tokyo have succeeded for the first time in verifying Einstein’s proposal of the non-locality of a single quantum: the idea that a single photon diffracted by a slit can spread over arbitrarily large distances, but is never detected in two or more places simultaneously.

This elusive phenomenon of non-locality in quantum mechanics, which has been termed “spooky action at a distance,” spurred a hundred years’ debate among physicists with Einstein’s proposal in 1909. Ever since, physicists have been making zealous efforts towards rigorous confirmation by highly efficient measurement devices. However, detection methods used so far have been for detecting photons as particles. In addition to low detection efficiency, since these methods can only detect the presence or absence of photons, it was theoretically impossible to rigorously verify Einstein’s proposal.

Graduate School of Engineering Professor Akira Furusawa, doctoral student Maria Fuwa and their collaborators utilized the wave-like degree of a photon as an electromagnetic wave and used a homodyne measurement technique to measure the photon amplitude and phase with high efficiency. They demonstrate it by splitting a single photon between two laboratories and experimentally testing whether the choice of measurement in one laboratory really causes a change in the local quantum state in the other laboratory.

This enabled the group to successfully verify the non-locality of a single photon with high precision and rigor. The experiment also verifies the entanglement of the split single photon even when one side is untrusted.

M. Fuwa, S. Takeda, M. Zwierz, H. M. Wiseman, and A. Furusawa. Experimental proof of nonlocal wave function collapse for a single particle using homodyne measurements. Nat Commun, 6, 03 2015.