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The observation and control of ultrafast phenomena is of growing importance in photonics, providing new insights into science as well as industrial research. The latest issue of Technology Focus delves into the topic with articles on shaping of ultrashort laser pulses, laser-based X-ray generation and time-gated imaging.
By exploiting the Stark manifold resonance in a crystalline host, scientists report laser cooling of ytterbium-doped LiYF4 crystals from room temperature to ∼155 K, with a cooling power of 90 mW. This is the lowest temperature achieved without using cryogens or mechanical refrigeration, surpassing the performance of multistage Peltier coolers.
Researchers have constructed a terahertz quantum cascade laser using quasi-periodic distributed feedback gratings based on the Fibonacci sequence. Features that go beyond traditional distributed feedback lasers are demonstrated, such as directional output independent of the emission frequency and multicolour operation.
The first enhancement cavity for femtosecond ultraviolet pulses is demonstrated. More than 7 W of average ultraviolet power at an 81 MHz repetition rate, available to pump a nonlinear crystal inside the cavity, is exploited in an implementation of a powerful source for high-rate experiments with entangled multiphoton states.
The lack of effcient solid-state sources of single photons is impeding the further development of many fields including quantum communication, quantum information processing and metrology. Using an InAs quantum dot embedded in a GaAs photonic nanowire with carefully tailored ends, researchers demonstrate a record single-photon source effciency of 0.72 under optical pumping.
Distillation of entangled photons is essential for applications such as long-distance quantum communication and high-fidelity quantum teleportation. Distillation from Gaussian input states is experimentally realized, resulting in a large gain in entanglement.
Scientists demonstrate that a single 7.5-μm-diameter microdisk laser coupled to a silicon-on-insulator wire waveguide can work as an all-optical flip-flop memory. Under a continuous bias of 3.5 mA, flip-flop operation is demonstrated using optical triggering pulses of 1.8 fJ and with a switching time of 60 ps. This device is attractive for on-chip all-optical signal buffering, switching, and processing.
Fine control over the material structure within a volume gives rise to new physical phenomena and more freedom for designing spatial, spectral and temporal functions. A three-dimensional scattering approach to the design of aperiodic volume optical elements is presented, expanding the traditional capabilities of volume holography, photonic crystals and diffractive optics.
The optical Kerr effect is a well-known phenomenon in which an electric field creates birefringence in a material. Researchers have now demonstrated this effect using single-cycle terahertz pulses — instead of optical pulses — in a variety of liquids.
On-demand single-photon sources with high efficiency are required to realize many of the applications of quantum optics. By exploiting photonic mode transformation in a tapered nanowire, researchers have created a source that has an unprecedented extraction efficiency over an extremely broad spectral range.
Ferroelectrics may have a bright future for solar-energy generation, following the report that the domain walls of such materials can be engineered to exhibit a photovoltaic effect with an impressively high voltage output.
Optical loss degrades quantum correlations, hindering the use of quantum quadrature entanglement for many applications. Researchers have now experimentally demonstrated that this entanglement can be recovered using photon subtraction.
The use of a specially designed cavity to enhance the intensity of femtosecond ultraviolet pulses dramatically increases the rate at which non-classical states of light can be produced.
Researchers in Germany have set up a company to manufacture custom-made optics for ultrafast applications. Nadya Anscombe finds out about the company's products and its plans for the future.
Table-top sources that generate both extreme ultraviolet light and soft X-rays through high-harmonic generation of ultrafast infrared laser pulses look set to perform tasks previously accessible using only large-scale synchrotrons.
Cameras equipped with an image intensifier make it possible to image ultrafast and low-light events and are proving of particular importance for combustion studies.
The use of pulse-shaping technology to optimize the temporal and spectral properties of ultrashort light pulses can enhance their utility in many applications.
Andreas Stingl, CEO of Austrian company Femtolasers, talks to Nadya Anscombe about the market for femtosecond lasers and their wide variety of applications.
A new method for designing aperiodic volume optical elements will offer researchers more degrees of freedom in the design of optical devices. Rafael Piestun explained to Nature Photonics how this method may lead to a myriad of applications in beam-shaping and imaging.
