3rd quarter 2010
4th quarter 2010
A Fabry-Pérot arrangement may enhance the transmission of light through sub-wavelength holes in metal films
by a factor of 20 or more.
Appl. Phys. B 100, 169-172 (2010) 100, 169-172 (2010)
A Whispering-Gallery-Mode Resonator is fabricated out of a 500-µm-thick lithium niobate crystal on a lathe at 40 000 rpm. The diamond blade is shifted along the horizontal axis, while the rotating crystal is moved along the vertical axis.
1st quarter 2010
2nd quarter 2010
Cascaded nonlinear processes in optical parametric oscillators based on
periodically-poled lithium niobate allow to generate narrow-band,
tunable, and diffraction-limited continuous-wave terahertz radiation
with more than 2 µW power.
Optics
Express 17, 22303-22310 (2009)
Newly discovered absorption bands between 2500 and 2800 nm in congruent lithium niobate crystals in the as-grown state and after high-temperature
annealing for extraordinarily polarized light. As an application of these low-loss annealed crystals, the operation of a 1550-nm-pumped singly-resonant
continuous-wave optical parametric oscillator, resonant around 2600 nm, was demonstrated for the first time (collaborative project with
Stanford University and Crystal Technology, Inc.).
Optics
Letters 35, 1070-1072 (2010)
3rd quarter 2009
4th quarter 2009
Cascaded nonlinear processes are observable in optical parametrical
oscillators at high pump powers. Here the primary signal wave acts as the
pump wave for the generation of terahertz radiation.
Optics
Express
17, 87-91 (2009)
A light brush cleans nonlinear crystals, suppresses
optical damage, and hence enables efficient generation of high-power laser
light.
Nature
Photonics 3, 510-512 (2009)
(Download
information)
1st quarter 2009
2nd quarter 2009
Image of a whispering-gallery mode (WGM) coupled out (left) and a
simulation of the corresponding mode in the resonator (right). The
simulation gives the intensity of the light along a vertical cut of the
resonator, whose surface is shown in white. It corresponds to the near
field of the outcoupled mode. The values q, l, m are the quantum numbers
of the mode.
3rd quarter 2008
4th quarter 2008
Tunable continuous-wave terahertz radiation is generated by photomixing
the signal waves of a dual crystal optical parametric oscillator.
New J.
Phys.
10, 073003 (2008)
Ultraslow shock-waves of electron density are
obtained through
thermo-electrical oxidization of iron-doped lithium niobate crystals.
Click onto the image in order to start the movie.
Phys. Rev. Lett. 101,
116601 (2008)
1st quarter 2008
2nd quarter 2008
In December 2007 two laser beams were sent over the
city of Bonn for one week to promote the Heinrich-Hertz-Day.
The green one was directed to the Telekom headquarters. (Photo: Jens Kießling)
An intra-cavity amplifier, being pumped incoherently (pump power PD), is able to lower the
threshold of an optical parametric
oscillator by more than one order of magnitude.
Opt.
Express
16, 5662-5666 (2008)
3rd quarter 2007
4th quarter 2007
Wavelength of light of a high-power laser diode
stabilized with the help of a Bragg grating. This Bragg grating stabilizes
the emission wavelength over a large range of diode currents and diode
temperatures.
Cage for light. The bright round disk is a WGM-resonator made of a lithium niobate crystal. Once light is inserted into the resonator by a prism, it is kept inside by total internal reflection, and very high intensities can be achieved.
1st quarter 2007
2nd quarter 2007
Transmission of a focussed 5 W beam of 532 nm wavelength through
undoped congruent LiNbO3 super-oxidized
(left) and as-grown (right); the treatment avoids the so-called "optical
damage".
Transmission of blue light (wavelength 488 nm) through a hole of 150 nm
diameter in a silver film on top of a lithium niobate crystal. A hologram
in the crystal confines the light by the so-called phase conjugation such
that it is transmitted through the hole (photograph: Diploma Thesis
Thorsten Hoffmann).
3rd quarter 2006
4th quarter 2006
All-optical switching: A red light beam propagates through a suspension of
silver nano particles. Without blue light (left) the red beam is not
affected, but with blue light
turned on (right) the liquid acts as a defocussing lens. Optical
nonlinearities of the nanoparticle suspension are the origin of this
effect [J. R. Adleman, H. A. Eggert,
K. Buse, D. Psaltis
(a) Photorefractive ferroelectric crystals (e. g., Cu:PPLN = Copper-doped Periodically-Poled Lithium Niobate) allow multiplexing of rectangular domain gratings, that contain many Fourier orders with well-defined spatial frequencies, with sinusoidal space charge gratings generated by interference of two plane waves. The Fourier spectrum of the multiplexed grating includes sum and difference frequencies. (b) The components of the mixed grating are detected by Bragg diffraction: several diffracted beams are observed (numbered by s). The angular distance between neighboring beams is determined by the PPLN grating vector whereas the holographic grating vector defines the center position of the diffraction pattern. The graph shows the diffraction efficiencies ηs of the diffracted beams as a function of the angle of incidence θ relative to the normal of the crystal surface. The results are of relevance for, e.g., nonlinear-optical components with integrated refractive index gratings [Opt. Lett. 31, 583 (2006)].
1st quarter 2006
2nd quarter 2006
Photon division: Op
tical parametric oscillator (pump beam: 1030 nm,
17 W, signal beam: 1470 nm, idler beam: 3440 nm, 1.8 W). The nonlinear
material is periodically poled lithium niobate. Additionally, various
visible light lines are created due to sum frequency mixing.
Scanning force microscopy images (6 x 3.5 µm²) of the vertical (a) and lateral forces (b) observed at domains of a
LiNbO3 crystal. The measured movements of the cantilever (c) result from the converse
piezoelectric effect (domain faces in a) and electrical field gradients at the crystal surface (domain boundaries in a, b)
http://arxiv.org/abs/cond-mat/0602414
