An off-center waveguide enables light to be efficiently extracted from nanoscale lasers.
Semiconductor optical devices are becoming increasingly commonplace. For example, light-emitting diodes, as they become more power efficient, are rapidly replacing conventional light bulbs. Lasers too are now found in every barcode scanner and compact-disc reader.
Computer simulations show that efficient light extraction from a nanoring plasmonic laser can occur when a waveguide is connected flush with one edge of the device. Modified from Ref. 1 and licensed under CC BY-NC 3.0
Copyright : 2014 C. Lee et al.
When designing these devices, a crucial consideration is how best to get the light generated within the solid material out into the real world. Chee-Wei Lee at the A*STAR Data Storage Institute, Singapore, and international colleagues have now proposed a light-extraction scheme that is capable of transferring over half the light created by a submicrometer-scale laser into a waveguide(1).
Plasmonic lasers are the smallest lasers created to date — they can even be smaller than the wavelength of the light they emit. This counterintuitive property results from plasmons, which are hybrid electron–light particles created by coupling light with electrons in a metal.
Lee and his team considered the simplest plasmonic laser: a ring of a light-emitting semiconductor coated with a thin silver layer. Light can travel round and round inside the ring, which provides the optical cavity required in most laser devices.
What is more, this tiny laser can be bonded onto a silicon substrate to make it compatible with compact photonics-on-a-chip technology. Lee and his team used computer simulations to demonstrate that high extraction efficiency is obtained when a waveguide (a light-carrying submicrometer-wide semiconductor strip) is directly connected to the side of the laser.
The team used a numerical simulation technique called finite-difference time-domain to study the performance of waveguides of different widths connected at different points on the laser. Their models revealed that the optimal structure is an asymmetric one.
When the extraction waveguide is displaced from the center of the ring — so that the waveguide is flush with the edge of the cavity — it produces a peak out-coupling efficiency of 56 per cent (see image). “Our scheme, based on directly joining a waveguide, enhances light extraction by splitting the plasmon mode,” explains Lee.
Scientists have previously extracted light from plasmonic lasers by running a waveguide extremely close to, but not touching, the cavity ring. Light can leak across the gap between the laser and the waveguide through an effect called evanescent coupling.
But this approach requires precise control over the gap size and the optical properties of the material in the gap. The method developed by the team, however, can be implemented using much simpler device fabrication. “We are now in the process of actually realizing such a device,” says Lee.
1. Lee, C.-W., Singh, G. & Wang, Q. Light extraction — a practical consideration for a plasmonic nano-ring laser. Nanoscale 5, 10835–10838 (2013).
Lee Swee Heng | Research SEA News
New process for cell transfection in high-throughput screening
21.03.2016 | Laser Zentrum Hannover e.V.
Sustainable products: Fraunhofer LBF investigates recycling of halogen-free flame retardant
17.02.2016 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Since the completion of the human genome an important goal has been to elucidate the function of the now known proteins: a new molecular method enables the investigation of the function for thousands of proteins in parallel. Applying this new method, an international team of researchers with leading participation of the Technical University of Munich (TUM) was able to identify hundreds of previously unknown interactions among proteins.
The human genome and those of most common crops have been decoded for many years. Soon it will be possible to sequence your personal genome for less than 1000...
3D printing revolutionized the manufacturing of complex shapes in the last few years. Using additive depositing of materials, where individual dots or lines...
R2D2, a joint project to analyze and development high-TRL processes and technologies for manufacture of flexible organic light-emitting diodes (OLEDs) funded by the German Federal Ministry of Education and Research (BMBF) has been successfully completed.
In contrast to point light sources like LEDs made of inorganic semiconductor crystals, organic light-emitting diodes (OLEDs) are light-emitting surfaces. Their...
High resolution rotational spectroscopy reveals an unprecedented number of conformations of an odorant molecule – a new world record!
In a recent publication in the journal Physical Chemistry Chemical Physics, researchers from the Max Planck Institute for the Structure and Dynamics of Matter...
Strands of cow cartilage substitute for ink in a 3D bioprinting process that may one day create cartilage patches for worn out joints, according to a team of engineers. "Our goal is to create tissue that can be used to replace large amounts of worn out tissue or design patches," said Ibrahim T. Ozbolat, associate professor of engineering science and mechanics. "Those who have osteoarthritis in their joints suffer a lot. We need a new alternative treatment for this."
Cartilage is a good tissue to target for scale-up bioprinting because it is made up of only one cell type and has no blood vessels within the tissue. It is...
30.06.2016 | Event News
28.06.2016 | Event News
09.06.2016 | Event News
30.06.2016 | Health and Medicine
30.06.2016 | Life Sciences
30.06.2016 | Physics and Astronomy