Laser anniversary

This month sees the 50th anniversary of the laser, with a host of activities taking place in celebration.

Nadya Anscombe talks to Charles Townes, Nobel Prize winner and inventor of the maser, the forerunner to the laser, to find out how the invention of the laser came about and how he struggled to convince people of its importance.

Will graphene optoelectronics be able to displace silicon technology? Thomas Mueller explains that a new design of graphene photodetector is showing great promise.

A graphene-based photodetector with unprecedented photoresponsivity and the ability to perform error-free detection of 10 Gbit s⁻¹s data streams is demonstrated. The results suggest that graphene-based photonic devices have a bright future in telecommunications and other optical applications.

Entangled photons are efficiently generated from highly symmetric, site-controlled InGaAs/GaAs quantum dots grown in inverted pyramids. Fine-structure splitting of the intermediate exciton level is suppressed without the application of electric, magnetic or strain fields. Polarization entanglement is demonstrated by measurements of the two-photon density matrix and the confirmation of several entanglement criteria.

Scientists report a mode-locking regime of an erbium-doped fibre laser in which the laser pulse evolves as a similariton in the gain segment of the cavity and transforms into a soliton in the rest of the cavity. The findings constitute the first observation of amplifier similaritons in a laser cavity and are likely to be applicable to various other nonlinear systems.

A Yagi–Uda directional antenna — the work horse of radiofrequency communications for more than 60 years — has now been demonstrated at visible wavelengths. An array of appropriately tuned nanoparticles replicate the reflecting and directing elements of the original design. Directional control of radiation from the nano-optical Yagi–Uda antenna was experimentally shown.

A noiseless linear amplifier for quantum states of an optical field is demonstrated. The amplifier is also used to enhance entanglement through a technique known as distillation. Such amplification and distillation may be useful for quantum cloning, metrology and communications.

Light is scattered out of a focusing beam when an inhomogeneous medium is placed between the lens and the focal plane. Now, scientists experimentally demonstrate that scattering can be exploited to improve, rather than deteriorate, the focusing resolution of a lens by using wavefront shaping to compensate for scattering.

By exploiting stochastic resonance — in which nonlinear coupling allows signals to grow at the expense of noise — scientists show that they can recover noise-hidden images propagating in a self-focusing medium. The findings pave the way for a variety of nonlinear instability-driven imaging techniques.

Precise spatial characterization of the origin of light emission from organic light-emitting diodes is important for improving the design of future devices and gaining valuable insight into their operation. Here, a characterization scheme that achieves this task with a spatial resolution better than 5 nm is reported.

Could optical technology offer a solution to the heat generation and bandwidth limitations that the computing industry is starting to face? The benefits of energy-efficient passive components, low crosstalk and parallel processing suggest that the answer may be yes.

The demonstration of a Yagi–Uda nano-antenna that operates at visible wavelengths gives hope for a convenient means of directing radiation patterns from nanoscale light sources such as single molecules and quantum dots.

Contrary to intuition, a disordered scattering medium can be exploited to improve, rather than deteriorate, the focusing resolution of a lens.

The use of a fabrication scheme for controlling the symmetry, uniformity and location of quantum dots has resulted in a superior source of entangled photon pairs.

A new femtosecond fibre laser design combines two distinct regimes of nonlinear dynamic attraction within a single cavity to yield robust and low-noise performance.

The optics of disordered materials is rich and full of surprises. Researchers have now found a new form of stochastic resonance in which an image beam is resonantly amplified by noise.

A scheme for polishing glass to an angstrom-scale surface quality and an all-optical pH measurement technique were just two of the elegant ideas presented at this year's spring meeting of the Japan Society of Applied Physics.

The initial concept of the laser was pioneered at Bell Labs, as were many other technologies that are fundamental to the photonics industry. Nadya Anscombe finds out how the company has changed in recent years and what technologies are being researched at Bell Labs today.

The Nd:YAG was one of the first ever industrial lasers, and even today it still has many advantages over other laser technologies. Competition from newer laser technologies, however, has made its evolution critical to its survival.

The excimer laser is synonymous with precision. Today it is enabling the production of integrated circuits and nextgeneration displays, as well as new breakthroughs in eye surgery.

The semiconductor laser has revolutionized the way the world communicates, and it is continuously evolving with our ever-increasing demand for higher bandwidths.

When the Ti:Sapphire laser was first invented, it took the research community by storm. Today, it has an important role in imaging, spectroscopy and many other applications.

With its high wall-plug efficiency and record-breaking power output, the fibre laser has made the use of lasers in manufacturing more acceptable and cost-effective.

Since their invention, quantum cascade lasers have made considerable progress in terms of their wavelength range and efficiency. Today, they have important applications in environmental science, process control and medical diagnostics.