We use patterned 3D multi-spot illumination to perform neuronal multi-site stimulation in rat brain tissue. Using a spatial
light modulator, we holograpically project 3D light fields for multi-site two-photon photolysis of caged neurotransmitters
to generate synaptic inputs to a neuron. Controlled photostimulation of multiple synapses from various locations in the
dendritic tree provides a way to analyze how neurons integrate multiple inputs. Our holographic projection setup is
incorporated into a two-photon 3D imaging microscope for visualization and for accurate positioning of specific
uncaging sites along the neuron's dendritic tree. We show two-photon images and the neuron's response to holographic
photostimulation of synapses along dendrites.
We demonstrate a multi-functional system capable of multiple-site two-photon excitation of photo-sensitive compounds
as well as transfer of optical mechanical properties on an array of mesoscopic particles. We use holographic projection of
a single Ti:Sapphire laser operating in femtosecond pulse mode to show that the projected three-dimensional light
patterns have sufficient spatiotemporal photon density for multi-site two-photon excitation of biological fluorescent
markers and caged neurotransmitters. Using the same laser operating in continuous-wave mode, we can use the same
light patterns for non-invasive transfer of both linear and orbital angular momentum on a variety of mesoscopic particles.
The system also incorporates high-speed scanning using acousto-optic modulators to rapidly render 3D images of neuron
samples via two-photon microscopy.
We present simulations and experimental results on encoding information both in the longitudinal and transverse
directions of an optical beam reflected from an asymmetric pit. The method does not require interferometric
detection but is based on intensity measurements using a simple quadrant detector. In addition, we also discuss
the implementation of this scheme in an optical recording setup and make an analysis of the crosstalk between
We use the holographic method to project an arbitrary array of diffraction-limited focal spots suitable for multi-site twophoton
excitation. The spot array can be projected arbitrarily within a three-dimensional (3D) volume, while the fourth
dimension in time is attributed to high temporal resolution via high-speed non-iterative calculation of the hologram using
a video graphics accelerator board. We show that the spots have sufficient energy and spatiotemporal photon density for
localized two-photon excitation at individual spots in the array. The significance of this work points to 3D microscopy,
non-linear micro-fabrication, volume holographic optical storage and biomedical instrumentation. In neuroscience, timecritical
release of neurotransmitters at multiple sites within complex dendritic trees of neurons can lead to insights on the
mechanisms of information processing in the brain.
Quantum correlations and entanglement are an important addition to the conventional properties of continuous
laser beams. They allow us to avoid, at least in principle, the limitations imposed by quantum noise and they
open new opportunities for the transfer and processing of quantum information. This manuscript reviews the
state of art in the creation, detection of quantum correlations and entanglement, shows the analogy to the
techniques based on single photons. It summarizes some of the recent advances in optical sensing and quantum
The quantum nature of light imposes a limit to the detection of all properties of a laser beam. We show how we can reduce this limit for a measurement of the position of a light beam on a quadrant detector, simultaneously in two tranverse directions. This quantum laser pointer can measure the beam direction with greater precision than a usual laser. We achieve this by combining three beams, one intense coherent and two vacuum squeeezed beams, with minimum losses into one spatially multimode beam optimized for this application.
We present methods of transforming the standard quadrature amplitude squeezing of a continuous-wave light beam to its Stokes parameters and transverse spatial modes statistics. These two states of light are called polarization squeezing and spatial squeezing, respectively. We present experimental results of the quadrature amplitude, polarization and spatial squeezing obtained with a common experimental setup based on optical parametric amplifiers. The transformations from quadrature amplitude to polarization and spatial squeezing are achieved with only simple linear optics.
Photons and laser beams provide an ideal situation to discuss some of the mysteries of quantum physics. There are many additional fundamental features which are not accessible with a classical system such as an electric current, which include: quantum noise, the uncertainty relation and correlations between different laser beams. Not only is the difference between the quantum behavior of photons and classical waves a curious effect, it is also important in many technical applications and forms the basis of future technologies, such as improved optical sensors or quantum cryptography. Using the example of a simple beam splitter and its effect on a laser beam one can explore these mysterious quantum effect with undergraduate students. We will discuss a systematic series of cases, using the beam splitter, which identify the difference between the quantum and the classical world. We will present the technical details of an experiment suitable for third year students that demonstrate genuine quantum noise effects.
Solid state laser sources, such as diode-laser pumped Nd:YAG lasers, have given us a cw laser light of high power with unprecedented stability and low noise performance. In these lasers most of the technical sources of noise can be eliminated and thereby allow operation close to the theoretical limit set by the quantum properties of the light. We present progress in the experimental realization of such lasers. These investigations include the control of noise by electronic feedback, passive external cavities; and the reliable generation of amplitude squeezed light through second harmonic generation. At the same time we have developed theoretical models describing the quantum noise properties of coupled systems of lasers and cavities. The agreement between our experimental results with noise spectra calculated with our realistic theoretical models demonstrates the ability to predict the performance of various laser systems.