Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The seeing power of frogs

26.01.2015

A quantum light source proves that light-sensitive cells in frog eyes can detect single photons

Miniature light detectors in frog eyes known as retinal rod cells are directly and unambiguously shown to detect single photons of light — an astounding sensitivity considering that a humble 60 watt light bulb spews out a staggering 1020 photons per second. Using a specially developed light source that generates single photons, a new A*STAR study finds that a rod cell has an almost one-in-three chance of detecting an incoming photon.


Single photons from a tapered optical fiber (right) are directed at a pipette holding a rod cell taken from a frog’s retina.

Reproduced, with permission, from Ref. 1 © 2014 American Physical Society

Scientists have known for some time that rod cells are sensitive to single photons. This was inferred based on statistical modeling in studies that used classical light sources such as lamps, lasers and light-emitting diodes that generate a statistical distribution of photons. In contrast, the light source developed by Leonid Krivitsky and co-workers at the A*STAR Data Storage Institute and A*STAR Institute of Medical Biology is a truly single-photon source and hence eliminates the need to statistically analyze measurement results, thus enhancing measurement accuracy1.

“Our method is both direct and universal,” notes Krivitsky, “as it is not based on any particular statistical model of the cell response and thus does not involve any indirect assumptions.”

In the developed light source, a nonlinear optical crystal is irradiated with light from an ultraviolet laser. Most photons pass directly through the crystal, but approximately one in a million is split into two visible-light photons having twice the wavelength (532 nanometers) of the original photon (266 nanometers). One of these two photons is detected by a photodiode and used to trigger an acousto-optical modulator, causing it to divert the second photon to a tapered optical fiber directed at a pipette containing a rod cell from a frog’s eye (see image). Any signal produced by the rod cell is then detected.

Racing against the clock, since rod cells lose their viability after one to two hours, the researchers measured ten rods cells taken from ten different frogs. They found an average quantum efficiency of approximately 30 per cent — very close to that of human rod cells estimated from behavioral experiments. Krivitsky notes that rod-cell efficiency is comparable to the quantum efficiencies of state-of-the-art man-made single-photon detectors such as photomultipliers (40 per cent) and avalanche photodiodes (50 per cent); remarkably, rod cells occupy an area of only 5 by 50 micrometers and contain their own power supply.

The new light source could be further used to investigate how the quantum efficiency varies with wavelength, since it is easy to vary the wavelength of the generated single photons.

The A*STAR-affiliated researchers contributing to this research are from the Data Storage Institute and the Institute of Medical Biology. More information about the group’s research can be found at the Advanced Concepts & Nanotechnology webpage.

Reference:
[1] Phan, N. M., Cheng, M. F., Bessarab, D. A. & Krivitsky, L. A. Interaction of fixed number of photons with retinal rod cells. Physics Review Letters 112, 213601 (2014).


Associated links
A*STAR article

A*STAR Research | ResearchSEA
Further information:
http://www.researchsea.com

More articles from Physics and Astronomy:

nachricht APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie

nachricht First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied Science

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>