Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Clamping down on causality by probing laser cavities

30.08.2017

By monitoring the optical response of an externally probed laser cavity before and after gain clamping, a University of Central Florida and Yale collaboration reveals the underlying mechanisms driving the cavity's responses

Since the realization of the first laser cavity countless questions have been asked for which laser light has provided the answer. Numerous questions have also been posed in an effort to improve on our abilities to produce lasers with various performance specifications and wavelengths. A question that was not asked until recently is - what happens if you shine a laser beam through another laser cavity? It may not seem a practical question to ask experimentally, but after studying how externally incident light interacts with an active laser cavity in quantitative detail, the answer turns out to offer devices with new, seemingly paradoxical optical capabilities.


a) A lasing cavity is probed with an external signal. (b) Measured reflection from and transmission through the cavity as a function of gain, showing an increase until lases commences followed abruptly by clamping. The device becomes a transparent perfect mirror a pre-lasing gain value: reflection in 100 percent but the transmission is finite.

Credit: Ayman Abouraddy, University of Central Florida's CREOL

Now, an even closer look at these capabilities has provided a unique window into fundamental physics and optical behaviors. The collaboration researching these laser cavity interactions, from the University of Central Florida's College of Optics and Photonics (CREOL) and Yale University, developed a perfectly reflecting one-way mirror, offering truly concealed observation windows; something passive materials can only approximate.

Probing deeper into the mechanism of this paradoxical behavior, they have also now revealed fundamental aspects of what governs the optical responses and a direct view of causality's role. Ayman Abouraddy, University of Central Florida's CREOL - Multi-Material Optical Fiber Devices group, will present their group's findings at Frontiers in Optics + Laser Science APS/DLS (FIO + LS), held 17-21 September 2017 in Washington, DC.

... more about:
»APS »DLS »FiO »Laser »OSA »energy flow »fundamental physics »mirror »optics

"A cavity is one of the fundamental components we have in optics - it's basically two mirrors in front of each other," Abouraddy said. "We've been looking at what would happen if I send a beam of light through such a cavity with gain inside as I gradually crank up the amount of gain. We're studying what happens to light that is sent through a cavity if the cavity is active."

By changing the amount of gain, the cavity's optical response to a separate incident laser (of a different wavelength) also changes. This active component measurably changes the reflection and transmission, depending the active gain level of the cavity.

"As we increase the amount of gain, the cavity will lase on its own. For our research today, we are more interested in what happens to a signal that I am sending through that cavity," Abouraddy said.

When the cavity does begin to lase, however, a fascinating and important shift in the behavior appears. At that point, both reflection and transmission amplification top out, although the power of the probing signal remains linearly related to the output. This also demonstrates the effect is not near saturation.

"The cavity is not allowed to amplify beyond a certain limit after you hit lasing," said Abouraddy. This effect, known as gain clamping, is part-and-parcel to stable functioning of the laser. The similar response to externally incident light, however, which lends to a truly transparent perfect mirror, is not only novel but offers new insight into fundamental physics.

The team's experimental demonstration used a fiber optic cavity in which they separated the forward and backwards travelling light. When they closely investigated the dynamics of directional energy flow in the cavity as that gain was increased, what they found related to fundamental physical principles.

Abouraddy explains that at sufficient gain, as light makes trips in the cavity in both directions, a null in the energy flow where the two directions cancel gradually creeps deeper into the cavity. The behavior of this null links a laser's fundamental threshold to a direct demonstration of causality's limits.

"At the lasing threshold, that null reaches midway in the cavity. It turns out increasing the gain further, that null refuses to move ahead, and it's pinned to the middle of the cavity," he said. "That is why when we increase the gain, we don't see further amplification. Now the beauty of this whole thing is it turns out that it is connected to causality. If that null were to move further beyond the midway of the cavity, which would be a violation of causality. In this case, one would get an output from it before you sent an input."

###

About the Presentation

The presentation entitled "Gain-Clamping for an Externally-Incident Field Passing through a Laser Cavity," by Ali Kazemi Jahromi, will take place from on Tuesday, 19 September at the Washington Hilton, Washington DC, USA.

Media Registration

A media room for credentialed media and analysts will be located on-site. Media interested in attending the event should register on the FiO + LS website: Media Center.

About FiO + LS

Frontiers in Optics is The Optical Society's (OSA) Annual Meeting and held together with Laser Science, a meeting sponsored by the American Physical Society's Division of Laser Science (DLS). The two meetings unite the OSA and APS communities for five days of quality, cutting-edge presentations, in-demand invited speakers and a variety of special events spanning a broad range of topics in optics and photonics--the science of light--across the disciplines of physics, biology and chemistry. The exhibit floor will feature leading optics companies, technology products and programs. More information at: FrontiersinOptics.org.

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.

Media Contacts:
Rebecca B. Andersen
The Optical Society
randersen@osa.org
+1 202.416.1443

Joshua Miller
The Optical Society
jmiller@osa.org
+1 202.416.1435

http://www.osa.org 

Joshua Miller | EurekAlert!

Further reports about: APS DLS FiO Laser OSA energy flow fundamental physics mirror optics

More articles from Physics and Astronomy:

nachricht Researchers discover link between magnetic field strength and temperature
21.08.2018 | American Institute of Physics

nachricht Smallest transistor worldwide switches current with a single atom in solid electrolyte
17.08.2018 | Karlsruher Institut für Technologie (KIT)

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: It’s All in the Mix: Jülich Researchers are Developing Fast-Charging Solid-State Batteries

There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.

The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

A paper battery powered by bacteria

21.08.2018 | Power and Electrical Engineering

Protein interaction helps Yersinia cause disease

21.08.2018 | Life Sciences

Biosensor allows real-time oxygen monitoring for 'organs-on-a-chip'

21.08.2018 | Medical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>