Semiconductor light sources

Although Nature Photonics may have had a face-lift, its mission to bring you a selection of the most exciting research findings in all areas of optics and optoelectronics remains the same.

The application of a very strong magnetic field is experimentally demonstrated to enable operation of terahertz quantum cascade lasers at much higher temperatures than usual. Lasing at a frequency of 3 THz is reported at up to 225 K when a field of 19.3 T is applied. The results validate theoretical predictions that quantum confinement is a route towards room temperature operation.

Applications of microdisk lasers are intrinsically limited by their planar and isotropic emission. Now, by implementing appropriate diffraction gratings along the disk circumference, scientists present a vertically emitting terahertz quantum-cascade microdisk laser, shedding light on the fabrication of arrays of single-mode, highly collimated and powerful terahertz sources.

Scientists report a dual-wavelength quantum cascade laser that lases at wave factors k ≈ 0 and k ≈ 3.6 × 10⁸ m⁻¹. The finding may change the conventional idea that population inversion of lasing occurs only at k ≈ 0 and give ways on designing intersub-band devices with high k-space.

The ability to modulate optical plasmons, propagating along a metal–dielectric waveguide, on the femtosecond time scale suggests that plasmons may be a suitable data carrier for future ultrasfast communication applications.

A monolithically grown Ge/Si avalanche photodetectors (APD) with a gain–bandwidth product of 340 GHz, the highest value for any APDs operating at 1,300 nm, and a sensitivity equivalent to commercially available III-V compound APDs is reported. The excellent performance paves the way to achieving low-cost, CMOS-based, Ge/Si APDs operating at data rates of 40 Gb s⁻¹ or higher, where the performance of III-V APDs is severely limited.

The European Commission has identified photonics as a key technology for the future health of European industry. Nature Photonics spoke to Gustav Kalbe, Head of Sector at the Photonics Unit, about how he and his colleagues are influencing photonics research.

Larry Coldren from the University of California at Santa Barbara, USA, speaks to Nadya Anscombe about recent progress in the performance of semiconductor light sources.

The demonstration in this issue that strong magnetic confinement of electrons can dramatically increase the operating temperature of terahertz quantum cascade lasers is good news for the dream of reaching room temperature. Nature Photonics spoke with Qing Hu about the result and the future prospects.

Optical communication makes good use of sensitive avalanche photodiodes, typically made from group III–V semiconductor compounds. New research shows that silicon may be a viable alternative material for realizing such detectors with better performance.

How can we capture ultrafast optical signals in real time? A time lens is one possibility — able to image the temporal profile of a short optical signal, analogous to a conventional lens. Such a device has now been created on a silicon chip.

The demonstration that lasing at high-k wavevectors is possible in a quantum cascade laser may open new avenues for the design of intersub-band devices.

Recent research suggests that plasmonics may offer a route to the development of modulators with terahertz bandwidths, many orders of magnitude faster than today's devices.

By applying an extremely large magnetic field to break a semiconductor's energy bands into discrete levels, researchers have shown that it is possible for terahertz quantum cascade lasers to operate at unprecedented temperatures and wavelengths.

Using clever device engineering, European researchers have created vertically emitting microcavity lasers, potentially paving the way towards powerful terahertz sources and detectors useful for imaging and biological sensing.

German company M2K Laser was the first in the world to successfully commercialize tapered diode lasers, and is currently the only one making gallium antimonide devices. The company's managing director speaks to Nadya Anscombe about its strategy and future.

The commercialization of long-wavelength vertical-cavity surface-emitting lasers (VCSELs) is gaining new momentum as the telecoms market shifts from long-haul applications to local and access networks. These small, power-efficient devices offer several advantages over traditional edge-emitters.

The world's first full-scale production-line for quantum dot lasers is due to come on-stream this year, promising to deliver devices, which, unlike conventional semiconductor sources, will function at high temperatures.

The unique structure and properties of the quantum cascade laser have enabled scientists to gain access to a valuable region of the electromagnetic spectrum — the mid-infrared.