Tiny sensor lays groundwork for precision X-rays detection via endoscopy

March 28, 2017

WASHINGTON -- Using a tiny device known as an optical antenna, researchers have created an X-ray sensor that is integrated onto the end of an optical fiber just a few tens of microns in diameter. By detecting X-rays at an extremely small spatial scale, the sensor could be combined with X-ray delivering technologies to enable high-precision medical imaging and therapeutic applications.

"We want to develop this technology so that it could be used in radiotherapy, for example," said Thierry Grosjean, from FEMTO-ST Institute, The National Center for Scientific Research, France. "Specifically, the sensor could allow a real-time measurement of how much radiation is being delivered to a tumor via endoscopy."

In The Optical Society (OSA) journal Optics Letters, the researchers demonstrate their new X-ray sensor using low energy X-rays. They say that the same principle should work with the high-energy X-rays used for medical applications such as imaging and radiotherapy.

Controlling light

Like many of today's X-ray applications, the new sensor uses indirect detection. Rather than directly sensing X-rays, this method uses a special detector called a scintillator, which absorbs the X-rays and then emits light that is detected by an optical camera.

Achieving indirect X-ray detection on a small scale is challenging because scintillators emit photons in all directions. Scaling scintillators down to a very small size means that they will emit very few photons, making it almost impossible for the camera to catch enough photons at just the right angle. The researchers turned to optical antennas to help with this challenge.

Because optical antennas have been used to control the light emission from fluorescing molecules, the researchers thought they might also control light emitted by scintillators. "An optical antenna works much like a radio frequency antenna, offering a way to interconnect an emitter with free-space," said Grosjean. "We demonstrated that they can be used to control the directionality of the emission from scintillators."

Fabricating the sensor

To make the X-ray sensor, the researchers used an optical antenna to connect a single mode optical fiber with a tiny cluster of scintillators. They fabricated the optical antenna, just a few microns wide, onto the end of the fiber and grafted the scintillator cluster at its extremity. Light emitted from the scintillators hits the antenna and is directed into the fiber, where it travels to a remote optical detector. This setup keeps the electronics away from the X-rays, which protects electronics from damage after repeated use.

Although the X-ray sensor fabrication required a clean room facility, the researchers said it was not a difficult or expensive process. They are currently working on procedures that might make it even easier to graft the scintillators onto the fiber antenna.

From their experiments, the researchers estimated that the sensor has a spatial resolution on the order of 1 micron, which they are working to increase to about 100 nanometers. This improved resolution would allow the device to distinguish chemical components in composite materials by using the fiber tip to conduct low-energy X-ray scanning microscopy.

In addition to expanding the technology to work with the high-energy X-rays required for medical applications, the researchers are also investigating whether optical antennas could enable faster X-ray detectors. Since the devices have been shown to shorten the time between light absorption and light emission in fluorescence processes, the antennas might also shorten the time between X-ray absorption and light emission within scintillators - thus creating a faster way to detect X-rays.
Paper: Z. Xie, H. Maradj, M.-A. Suarez, L. Viau, V. Moutarlier, C. Filiatre, C. Fauquet, D. Tonneau, T. Grosjean, "Ultracompact X-ray dosimeter based on scintillators coupled to a nano-optical antenna," Opt. Lett., Volume 42, Issue 7, 1361-1364 (2017).
DOI: 10.1364/OL.42.001361.

About Optics Letters

Optics Letters offers rapid dissemination of new results in all areas of optics with short, original, peer-reviewed communications. Optics Letters covers the latest research in optical science, including optical measurements, optical components and devices, atmospheric optics, biomedical optics, Fourier optics, integrated optics, optical processing, optoelectronics, lasers, nonlinear optics, optical storage and holography, optical coherence, polarization, quantum electronics, ultrafast optical phenomena, photonic crystals and fiber optics.

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts. For more information, visit osa.org/100.

Media Contacts:

Rebecca B. Andersen
The Optical Society
+1 202.416.1443

Joshua Miller
The Optical Society
+1 202.416.1435 http://www.femto-st.fr/en/

The Optical Society

Related Optical Fiber Articles from Brightsurf:

Graphene controls laser frequency combs in fiber
Tuning laser frequency combs electrically can enrich diversity of comb outputs and help to stabilize them actively.

Asymmetric optical camouflage: Tuneable reflective color accompanied by optical Janus effect
Deliverying viewing-direction sensitive information display across single sheet of transreflective window is introduced.

Revealing the reason behind jet formation at the tip of laser optical fiber
When an optical fiber is immersed in liquid, a high temperature, high speed jet is discharged.

Rochester researchers document an optical fiber beyond compare
A new anti-resonant hollow core optical fiber produces a thousand times less ''noise'' interfering with signals it transmits compared to the single-mode fibers now widely used.

Brazilian researcher creates an ultra-simple inexpensive method to fabricate optical fiber
The conventional process requires costly large-scale equipment. The novel method can be executed in a single step by a device no larger than a microwave oven.

How bacteria adhere to fiber in the gut
Researchers have revealed a new molecular mechanism by which bacteria adhere to cellulose fibers in the human gut.

Brazilian researchers develop an optical fiber made of gel derived from marine algae
Edible, biocompatible and biodegradable, these fibers have potential for various medical applications.

A survey on optical memory and optical RAM technologies
The ability to store with light and built promising optical memories has been an intriguing research topic for more than two decades.

All-fiber optical wavelength converter
Wavelength conversion in all-fiber structure has extensive applications in new fiber-laser sources, signal processing, and multi-parameter sensors.

New design could make fiber communications more energy efficient
Researchers say a new discovery on a US Army project for optoelectronic devices could help make optical fiber communications more energy efficient.

Read More: Optical Fiber News and Optical Fiber Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.