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Lithography is a critical fabrication process underlying the computer and microelectronics industry as well as other applications. This issue of Technology Focus explores how techniques such as extreme ultraviolet lithography, nanoimprint lithography and direct laser writing are evolving to meet the needs of manufacturers.
John Warlaumont, vice president of advanced technologies at SEMATECH, a consortium of the world's chip manufacturers, talks to Nadya Anscombe about the future of optical lithography.
Few-cycle light pulses are important for attosecond science and extremely nonlinear optics. Alfred Leitenstorfer from the University of Konstanz spoke to Nature Photonics about how erbium-doped fibre laser technology can generate single-cycle pulses at telecommunications wavelengths.
Based on a passively phase-locked superposition of a dispersive wave and a soliton from two branches of a femtosecond Er-doped fibre laser, researchers demonstrate that single cycles of light can be achieved using existing fibre technology and standard free-space components. The pulses have a pulse duration of 4.3 fs, close to the shortest possible value for a data bit of information transmitted in the near-infrared.
A monolithically integrated CMOS-compatible source is demonstrated using an optical parametric oscillator based on a silicon nitride ring resonator on silicon. Generating more than 100 wavelengths simultaneously and operating at powers below 50 mW, scientists say that it may form the basis of an on-chip high-bandwidth optical network.
Through optical ‘hyper-parametric’ oscillation in a high-index silica glass microring resonator, scientists demonstrate a fully integrated CMOS-compatible low-loss multiple-wavelength source that has high differential slope efficiency at only a few tens of milliwatts of continuous-wave power. The achievement has significant implications for telecommunications and on-chip optical interconnects in computers.
Utilizing a self-referenced detection scheme based on the mode-splitting in an ultrahigh-Q microresonator, scientists realize the real-time in situ detection and sizing of single nanoparticles with radii as small as 30 nm. Labelling of the particles and a priori information on the presence of nanoparticles in the medium are not required, thus providing an effective platform for studying nanoparticles at the single-particle resolution level.
Nanocavity plasmons are exploited as a coherent optical source with tunable energy and to actively control the radiative channels of molecules. Intense resonance enhancement of both excitation and emission, in an effect called resonant hot-electroluminescence, is demonstrated for porphyrin molecules confined inside a nanocavity.
By combining Fourier transform spectroscopy with two frequency-shifted combs and cavity ring-down spectroscopy, scientists demonstrate a powerful new tool for ultrahigh sensitivity spectroscopy. The scheme can measure broadband, high-resolution spectra in tens of microseconds, does not require detector arrays and may allow tuning from terahertz to ultraviolet frequencies.
The generation of random bit sequences at a data rate of up to 300 Gbit s−1 — a rate many orders of magnitude faster than previously achieved — is realized by exploiting the output of a chaotic semiconductor laser. The randomness of the generated bits is verified by standard statistical tests.
A transistor that operates with photons rather than electrons is often heralded as the next step in information processing, but optical technology must first prove itself to be a viable solution in many different respects.
It has long been known that the optical resonances of ultrahigh-Q whispering gallery mode resonators can split under the influence of particle scattering. Now scientists have exploited this splitting to accurately determine particle sizes.
Optical parametric oscillators (OPOs) have now been realized in a CMOS-style process by exploiting nonlinear four-wave mixing. Such multiwavelength sources bring the prospect of ultrafast chip-to-chip optical data communications a step closer.
The entanglement of squeezed light beams is critical for quantum optical applications, but has so far been achieved with only two light beams. Now, researchers have surpassed this restriction and achieved entanglement with three beams of different colours. They also report a finite loss level for disentanglement of one beam from the other two.
By combining the output from two synchronized light sources, single-cycle laser pulses at the telecommunications wavelength of 1.5 μm have been successfully generated. The achievement is set to benefit ultrafast optical spectroscopy and attosecond science.
Start-up company Nanoscribe has developed table-top systems that can write intricate 3D structures not possible through other lithographic technologies. Nadya Anscombe finds out how the company was founded and what its plans are for the future.
Extreme ultraviolet lithography extends photolithography to much shorter wavelengths and is a cost-effective method of producing more-advanced integrated circuits. Although some infrastructure challenges still remain, this technology is expected to begin high-volume microchip production within the next three years.
Advances in nano-imprint lithography have moved the technology out of the laboratory and onto the production floor for use in a wide variety of photonic applications.
