| RESEARCH HIGHLIGHTS |


Their electrothermal element is called a


thermal unimorph and it consists of a comb- like set of silicon teeth interlaced with polymer expanders. Yang says: “Silicon has high thermal conductivity but small thermal expansion, while the polymer expander has a large thermal expansion coefficient, but low thermal conduc- tivity. When we resistively heat the element by applying electricity to the silicon, the polymer


expands, causing the silicon comb to bend.” Although the thermal unimorph can be


controlled with nanometer precision, its range of motion was previously too limited to be of practical use. Yang and his team overcame this limitation by adding a rotary lever action that magnified the stroke length by six times. “We are now exploring possible approaches to improve actuation speed performance,


such as designing a more efficient heat path, investigating new thermally active materials, and further miniaturization of the actuator footprint,” says Yang.


1. Lau, G. K., Yang, J., Tan, C. P. & Chong, N. B. An electro-thermally activated rotary micro- positioner for slider-level dual-stage positioning in hard disk drives. Journal of Micromechanics and Microengineering 26, 035016 (2016).


Spectroscopy: GHOSTLY MEASUREMENTS


A QUANTUM EFFECT ALLOWS INFRARED MEASUREMENTS TO BE PERFORMED BY DETECTING VISIBLE LIGHT, BRINGING OPPORTUNITIES FOR CHEAPER, BETTER PERFORMANCE SPECTROSCOPY


By weaving some quantum wizardry, A*STAR researchers have achieved something that appears to be a contradiction in terms — using visible light to perform spectroscopy at infrared wavelengths1. Even more mysterious is that the visible light does not even pass through the sample being measured. Infrared spectroscopy is widely used by


chemists to identify chemicals from their unique ‘fingerprints’ in the infrared region. However, infrared-light sources, elements and detectors


Crystal 1 Visible light


tend to have inferior performances and be more expensive than their visible-light counterparts. Now, Dmitry Kalashnikov at A*STAR Data


Storage Institute and his co-workers have hit on a way to overcome this problem and realize the best of both worlds — using visible light to perform measurements in the infrared region. They achieved this by exploiting a


quantum effect known as entanglement. In this phenomenon, two quantum particles (in this case, particles of light known as


Crystal 2


photons) are so intimately connected that changing the quantum state of one particle simultaneously alters the state of the other particle, even when the two particles are separated in space. This is the “spooky action at a distance” that Einstein famously objected to. Kalashnikov and his team used a special


Laser beam Infrared light Sample


By creating an entangled pair of one infrared photon and one visible light photon, A*STAR researchers can perform infrared measure- ments on a sample by detecting only the visible light photon.


22 A*STAR RESEARCH


Visible-light detector


crystal to create a pair of entangled photons, a visible one and an infrared one (see image). The infrared photon passed through a sample, whereas the optical one did not. The two photons then crossed at a second crystal and the visible photon was detected. Since any changes that the sample induced in the infrared photon were reflected in the visible photon, the team could infer information about the sample’s infrared properties by measuring only the visible photon. The researchers demonstrated the potential


of this technique by using it to measure the presence and concentration of carbon dioxide in samples of air. “We are confident that this method


will find a broad variety of practical applica- tions, for example in environmental monitoring and health diagnostics,” says Kalashnikov.


ISSUE 5 | OCTOBER – DECEMBER 2016


Modified by permission from Macmillan Publishers Ltd: Nature Photonics (Ref 2), copyright (2016)


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