Manufacturing Bits: May 26

Table-top EUV
Swinburne University of Technology has developed a table-top extreme ultraviolet (EUV) laser power source. The source could be used to develop a system for use in metrology and other applications.

The table-top setup is a new way to generate bright beams of coherent EUV radiation. It may offer a cost-effective alternative to large-scale facilities, such as synchrotrons or free-electron lasers. For example, researchers at the SLAC National Accelerator Laboratory are exploring the development of a high-power EUV source based on a storage ring technology.

Swinburne’s table-top EUV source technology is based on a “lensless” imaging technique called coherent diffractive imaging. In this technique, the images are reconstructed by a computer.

Table-top EUV system (Source: Swinburne University of Technology)

Researchers used the table-top laser setup to illuminate a gas cell of argon with two short laser pulses at different wavelengths. One beam generates harmonics in the EUV range. The second beam amplifies the radiation, based on a technology called optical parametric amplification.

Researchers used two multiple-cycle high-intensity laser pulses at 800nm and 1,400nm to generate EUV radiation. When the two pulses are applied, researchers have been able to enhance the flux of the coherent EUV radiation in the photon energy range.

Metrology is one application for the technology. “The ability to image nano-scale features with a conventional optical microscope is limited by the wavelength of the light used to illuminate the sample,” said Lap van Dao, a professor, on the university’s Web site. “One way to achieve higher spatial resolution is to use radiation with shorter wavelengths such as extreme UV radiation or ‘soft’ X-rays.”

Emeritus Professor Peter Hannaford added: “This research paves the way for the generation of intense radiation at still shorter wavelengths and ultimately to apply coherent diffractive imaging techniques to nano-scale structures and to biological samples in the water window region.”

Laser printer DSA
Swinburne University of Technology and the University of Science and Technology of China have developed a novel directed self-assembly (DSA) process.

The technology, called laser printing capillary-assisted self-assembly (LPCS), can be used to fabricate regular periodic structures. LPCS combines the advantages of fast laser printing and capillary force. Applications include chemistry, biomedicine, and microfluidic engineering.

In simple terms, vertical nanorods are devised using fast laser printing. The nanorods have various heights. Then, the material is washed in a solvent. The capillary force creates pillars. The pillars have unequal physical properties along different axes. “Using laser printing techniques we can control the size, geometry, elasticity and distance between tiny pillars – narrower than the width of a human hair – to get the self-assembly that we want,” said Swinburne researcher Yanlei Hu on the university’s Web site.

“A possible application of these structures is in on-chip micro-object trap-release systems which are in demand in chemical analysis and biomedical devices,” added researcher Ben Cumming.

Tiny beamsplitters
The University of Utah has developed what it claims is the world’s smallest beamsplitter.

The ultra-compact beamsplitter can divide light waves into two separate channels. The technology can be used in silicon photonics. Silicon photonics is an emerging technology, which makes optical devices out of silicon. It uses light to move large amounts of data at high speeds over a thin optical fiber, as opposed to using electrical signals over a copper cable.

Researchers from the University of Utah have fabricated a beamsplitter, based on a nanophotonics and polarization technology. The beamsplitter, which has a footprint of 2.4- × 2.4μm2, can be fabricated in a single lithography step. “A nonlinear optimization algorithm was used to design the device for λ0 = 1,550nm,” according to the University of Utah.

The overhead view of a new beamsplitter for silicon photonics. (Source: University of Utah)

The beamsplitter has an average transmission efficiency of greater than 70%, with a peak transmission efficiency of about 80%, according to researchers. It has an extinction ratio greater than 10dB within a bandwidth of 32nm.

This type of beamsplitter could be used in computers in about three years, thereby advancing the world of silicon photonics. “Light is the fastest thing you can use to transmit information,” said Rajesh Menon, a professor on the university’s Web site. “But that information has to be converted to electrons when it comes into your laptop. In that conversion, you’re slowing things down. The vision is to do everything in light. With all light, computing can eventually be millions of times faster.”