The research field of optical spectroscopy has already attracted attention of generations of scientists, starting with Fraunhofer's discovery of dark lines in the sun spectrum in 1814 followed by the work of Kirchhoff and Bunsen in 1859 explaining these lines as absorption of light in atoms and molecules.
Light confinement in microcavities: Quartz glass microresonators on a silicon chip allow to store light for long times corresponding to more than 1 million round trips of photons within the resonator. Depending on its wavelengths (color), the light is confined closer to the rim or more inside the resonator, respectively.
Within the last decade, the invention of optical frequency combs has revolutionized the field of spectroscopy and enabled measurements with previously unattainable precision. Now, MPQ scientists (from the "Laboratory of Photonics & Quantum Measurements" lead by EPFL tenure track professor T.J. Kippenberg) developed a novel measurement scheme for broadband and fast measurements of optical spectra utilizing the accuracy of an optical frequency comb and transferring it to an easy-to-use tunable diode laser. (Nature Photonics, AOP, August 2009, DOI:10.1038/nphoton.2009.138)
These tunable diode lasers can be swept in frequency (i.e. the "color" of the laser can be changed) to measure the spectral response of anything of interest, for example light absorption in gases but also the response of photonic elements in the growing field of nano-photonics. However, sweeping the frequency of a tunable diode laser alone does not allow for precise spectroscopic measurements, unless the instantaneous frequency of the diode laser at a certain time is known precisely.
Here, the new measurement scheme comes into play, enabling an "on-the-fly" calibration of the sweeping diode laser using an optical fiber laser based frequency comb. The achieved precision of the spectroscopic measurement is better than 1 MHz (note that the frequency of the laser light is around 200 THz, corresponding to a relative accuracy of 5x10 to the -9).As a first application, the newly developed spectroscopy scheme has been used by MPQ scientists Pascal Del'Haye and Dr. Arcizet to obtain absorption spectra of on-chip monolithic optical microresonators made of fused silica (so called microtoroids). These measurements allowed for the first time to analyze dispersion properties of these devices (conventional spectroscopy methods had so far failed due to the extremely narrow (sub-MHz) absorption lines of the microresonators). Numerical simulations as well as the experimental results show that the mode structure of microtoroids is extremely uniform, i.e. the optical modes that are supported by the device are nearly spaced equidistant. This surprising result is a consequence of the spatial shape of the optical modes within the resonator (leading to "red" modes at low frequencies being more confined inside the resonator than "blue" modes at high frequencies) that is partly compensated by a different material dispersion for different light frequencies (here, the "red" modes are travelling slower, i.e. the resonator seems to be larger for the "red" modes). "The small total dispersion of microtoroids makes them a well suited device for applications in microphotonics as well as for frequency comb generation via nonlinear optical
Nature Photonics, Advance Online Publication, August 2009, DOI:10.1038/nphoton.2009.138
Dr. Olivia Meyer-Streng | Max-Planck-Institut
Further reports about: > 1038/nphoton > Arcizet > MPQ > Max Planck Institute > Photonic > Quantum > absorption lines > conventional spectroscopy methods > high frequencies > optical microresonators > photonic elements > spectroscopic measurement > spectroscopy scheme > structure of microtoroids > sub-MHz
Applicability of dynamic facilitation theory to binary hard disk systems
08.12.2016 | Nagoya Institute of Technology
Will Earth still exist 5 billion years from now?
08.12.2016 | KU Leuven
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.
The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
08.12.2016 | Life Sciences
08.12.2016 | Physics and Astronomy
08.12.2016 | Materials Sciences