We present a framework to optimize the design of grating chips to maximize the atom number in a g... more We present a framework to optimize the design of grating chips to maximize the atom number in a grating-based magneto-optical trap (MOT). We evaluate the robustness of a grating-MOT against experimental parameters such as magnetic fields, laser intensity, etc. We also demonstrate a fast fabrication process for grating chips using laser lithography.
Light propagating in a moving medium is subject to light drag. While the light drag effect due to... more Light propagating in a moving medium is subject to light drag. While the light drag effect due to the linear refractive index is often negligibly small, the light drag can be enhanced in materials with a large group index. Here we show that the nonlinear refractive index can also play a crucial role in the propagation of light in moving media and results in a beam deflection. We perform an experiment with a rotating ruby crystal that exhibits a very large negative group index and a positive nonlinear refractive index. The negative group index drags the light opposite to the motion of the medium. However, the positive nonlinear refractive index deflects the beam along with the motion of the medium and hinders the observation of the negative drag effect. Hence, we show that it is necessary to measure not only the transverse shift of the beam but also its output angle to discriminate the light drag effect from beam deflection. Our work provides insight into applications for all-optical...
We propose tunable nonlinear antennas based on an epsilon-near-zero material with a large optical... more We propose tunable nonlinear antennas based on an epsilon-near-zero material with a large optical nonlinearity. We show that the absorption and scattering cross sections of the antennas can be controlled dynamically from a nearly superscatterer to a nearly superabsorber by changing the intensity of the laser beam. Moreover, we demonstrate that a hybrid nonlinear antenna, composed of epsilon-near-zero and high-index dielectric materials, exhibits nonreciprocal radiation patterns because of broken spatial inversion symmetry and large optical nonlinearity of the epsilon-near-zero material. By changing the intensity of the laser, the radiation pattern of the antenna can be tuned between a bidirectional and a unidirectional emission known as a Huygens source. Our study provides a novel approach toward ultrafast dynamical control of metamaterials, for applications such as beam steering and optical limiting.
Terahertz (THz) nonlinear optics is an emerging field enabled by recent developments in the gener... more Terahertz (THz) nonlinear optics is an emerging field enabled by recent developments in the generation of THz pulses with higher intensities. THz radiation can interact with the vibrational/rotational resonances of molecules. For example, vapour in the atmosphere shows a very rich absorption spectrum with hundreds of sharp resonances below 3 THz. We report on the first experimental demonstration of the nonlinear interaction of THz pulses with water vapour. We observed a strong nonlinear response of the vibration/rotation resonances to the THz pulses in the form of reverse saturation of absorption.
We investigate the propagation of light in different conditions that lead to exotic propagation o... more We investigate the propagation of light in different conditions that lead to exotic propagation of photons and use near-resonant light-matter interactions to enhance these effects. First, we study the propagation of light in a moving highly dispersive medium, namely rubidium atoms. Based on the special relativity the speed of light changes with the speed of the medium. However, this drag effect in a non-dispersive medium is very small and thus difficult to measure. We show that the drag effect is enhanced significantly when the moving medium is highly dispersive. Thus, with this enhancement even a slow motion can be detected. Next, we employ the large nonlinear response of rubidium atoms to accentuate the formation of optical caustics. Caustics are important as nature uses caustics to concentrate the energy of waves. Moreover, caustics can be formed in many physical systems such as water waves in oceans to amplify tsunamis or generate rogue waves. The connection of our study to thes...
Terahertz (THz) nonlinear optics is an emerging field thanks to recent developments in the genera... more Terahertz (THz) nonlinear optics is an emerging field thanks to recent developments in the generation of intense THz pulses. THz radiation interacts with the vibrational/rotational resonances of molecules. For example, water molecules in the atmosphere show a very rich absorption spectrum with hundreds of sharp resonances below 3 THz. We report on the first experimental demonstration of the nonlinear interaction of THz pulses with water vapor. We observed a strong nonlinear response of the vibration/rotation resonances to the THz pulses. The frequency response of the nonlinear Kerr coefficient is extracted from the experimental results.
We report on the nonlinear spectroscopy of water vapor at THz frequencies. Atmospheric water vapo... more We report on the nonlinear spectroscopy of water vapor at THz frequencies. Atmospheric water vapor has a rich spectrum with several strong resonances at frequencies below 3 THz, falling within the range of operation of most existing THz sources. We observe an extremely large nonlinear response to THz radiation at the positions of these resonances. Using the optical Kerr model for the nonlinear response, we estimate a minimum nonlinear refractive index of the order of 10^2 m^2/W. Our results provide insight into the energy levels of the water molecule and give a more accurate picture of its response to electromagnetic radiation, paving the way to more accurate THz spectroscopy, imaging and sensing systems, and thereby facilitating future emerging THz technologies.
A dense cloud of atoms with randomly changing positions exhibits coherent and incoherent scatteri... more A dense cloud of atoms with randomly changing positions exhibits coherent and incoherent scattering. We show that an atomic cloud of subwavelength dimensions can be modeled as a single scatterer where both coherent and incoherent components of the scattered photons can be fully explained based on effective multipole moments. This model allows us to arrive at a relation between the coherent and incoherent components of scattering based on the conservation of energy. Furthermore, using superposition of four plane waves, we show that one can selectively excite different multipole moments and thus tailor the scattering of the atomic cloud to control the cooperative shift, resonance linewidth, and the radiation pattern. Our approach provides a new insight into the scattering phenomena in atomic ensembles and opens a pathway towards controlling scattering for applications such as generation and manipulation of single-photon states.
Although some non-trivial photon number resolving detectors exist, it may still be convenient to ... more Although some non-trivial photon number resolving detectors exist, it may still be convenient to discriminate photon number states with the method of multiplexed detection. Multiplexing can be performed with paths in real space, with paths in time, and in principle with any degree of freedom that has a sufficient number of eigenstates and that can be coupled to the photon number. Previous works have addressed the probabilities involved in these measurements with Monte Carlo simulations, or by restricting the number of detectors to powers of 2, or without including quantum efficiency or noise. In this work we find an analytical expression of the detection probabilities for any number of input photons and any number of on/off photon detectors with a quantum efficiency $0\%\leq\eta\leq100\%$ and a false count probability $\varepsilon\geq0$. This allows us to retrodict the number of photons that we had at the input in the least unbiased way possible. We conclude our work with some examp...
We present a framework to optimize the design of grating chips to maximize the atom number in a g... more We present a framework to optimize the design of grating chips to maximize the atom number in a grating-based magneto-optical trap (MOT). We evaluate the robustness of a grating-MOT against experimental parameters such as magnetic fields, laser intensity, etc. We also demonstrate a fast fabrication process for grating chips using laser lithography.
Light propagating in a moving medium is subject to light drag. While the light drag effect due to... more Light propagating in a moving medium is subject to light drag. While the light drag effect due to the linear refractive index is often negligibly small, the light drag can be enhanced in materials with a large group index. Here we show that the nonlinear refractive index can also play a crucial role in the propagation of light in moving media and results in a beam deflection. We perform an experiment with a rotating ruby crystal that exhibits a very large negative group index and a positive nonlinear refractive index. The negative group index drags the light opposite to the motion of the medium. However, the positive nonlinear refractive index deflects the beam along with the motion of the medium and hinders the observation of the negative drag effect. Hence, we show that it is necessary to measure not only the transverse shift of the beam but also its output angle to discriminate the light drag effect from beam deflection. Our work provides insight into applications for all-optical...
We propose tunable nonlinear antennas based on an epsilon-near-zero material with a large optical... more We propose tunable nonlinear antennas based on an epsilon-near-zero material with a large optical nonlinearity. We show that the absorption and scattering cross sections of the antennas can be controlled dynamically from a nearly superscatterer to a nearly superabsorber by changing the intensity of the laser beam. Moreover, we demonstrate that a hybrid nonlinear antenna, composed of epsilon-near-zero and high-index dielectric materials, exhibits nonreciprocal radiation patterns because of broken spatial inversion symmetry and large optical nonlinearity of the epsilon-near-zero material. By changing the intensity of the laser, the radiation pattern of the antenna can be tuned between a bidirectional and a unidirectional emission known as a Huygens source. Our study provides a novel approach toward ultrafast dynamical control of metamaterials, for applications such as beam steering and optical limiting.
Terahertz (THz) nonlinear optics is an emerging field enabled by recent developments in the gener... more Terahertz (THz) nonlinear optics is an emerging field enabled by recent developments in the generation of THz pulses with higher intensities. THz radiation can interact with the vibrational/rotational resonances of molecules. For example, vapour in the atmosphere shows a very rich absorption spectrum with hundreds of sharp resonances below 3 THz. We report on the first experimental demonstration of the nonlinear interaction of THz pulses with water vapour. We observed a strong nonlinear response of the vibration/rotation resonances to the THz pulses in the form of reverse saturation of absorption.
We investigate the propagation of light in different conditions that lead to exotic propagation o... more We investigate the propagation of light in different conditions that lead to exotic propagation of photons and use near-resonant light-matter interactions to enhance these effects. First, we study the propagation of light in a moving highly dispersive medium, namely rubidium atoms. Based on the special relativity the speed of light changes with the speed of the medium. However, this drag effect in a non-dispersive medium is very small and thus difficult to measure. We show that the drag effect is enhanced significantly when the moving medium is highly dispersive. Thus, with this enhancement even a slow motion can be detected. Next, we employ the large nonlinear response of rubidium atoms to accentuate the formation of optical caustics. Caustics are important as nature uses caustics to concentrate the energy of waves. Moreover, caustics can be formed in many physical systems such as water waves in oceans to amplify tsunamis or generate rogue waves. The connection of our study to thes...
Terahertz (THz) nonlinear optics is an emerging field thanks to recent developments in the genera... more Terahertz (THz) nonlinear optics is an emerging field thanks to recent developments in the generation of intense THz pulses. THz radiation interacts with the vibrational/rotational resonances of molecules. For example, water molecules in the atmosphere show a very rich absorption spectrum with hundreds of sharp resonances below 3 THz. We report on the first experimental demonstration of the nonlinear interaction of THz pulses with water vapor. We observed a strong nonlinear response of the vibration/rotation resonances to the THz pulses. The frequency response of the nonlinear Kerr coefficient is extracted from the experimental results.
We report on the nonlinear spectroscopy of water vapor at THz frequencies. Atmospheric water vapo... more We report on the nonlinear spectroscopy of water vapor at THz frequencies. Atmospheric water vapor has a rich spectrum with several strong resonances at frequencies below 3 THz, falling within the range of operation of most existing THz sources. We observe an extremely large nonlinear response to THz radiation at the positions of these resonances. Using the optical Kerr model for the nonlinear response, we estimate a minimum nonlinear refractive index of the order of 10^2 m^2/W. Our results provide insight into the energy levels of the water molecule and give a more accurate picture of its response to electromagnetic radiation, paving the way to more accurate THz spectroscopy, imaging and sensing systems, and thereby facilitating future emerging THz technologies.
A dense cloud of atoms with randomly changing positions exhibits coherent and incoherent scatteri... more A dense cloud of atoms with randomly changing positions exhibits coherent and incoherent scattering. We show that an atomic cloud of subwavelength dimensions can be modeled as a single scatterer where both coherent and incoherent components of the scattered photons can be fully explained based on effective multipole moments. This model allows us to arrive at a relation between the coherent and incoherent components of scattering based on the conservation of energy. Furthermore, using superposition of four plane waves, we show that one can selectively excite different multipole moments and thus tailor the scattering of the atomic cloud to control the cooperative shift, resonance linewidth, and the radiation pattern. Our approach provides a new insight into the scattering phenomena in atomic ensembles and opens a pathway towards controlling scattering for applications such as generation and manipulation of single-photon states.
Although some non-trivial photon number resolving detectors exist, it may still be convenient to ... more Although some non-trivial photon number resolving detectors exist, it may still be convenient to discriminate photon number states with the method of multiplexed detection. Multiplexing can be performed with paths in real space, with paths in time, and in principle with any degree of freedom that has a sufficient number of eigenstates and that can be coupled to the photon number. Previous works have addressed the probabilities involved in these measurements with Monte Carlo simulations, or by restricting the number of detectors to powers of 2, or without including quantum efficiency or noise. In this work we find an analytical expression of the detection probabilities for any number of input photons and any number of on/off photon detectors with a quantum efficiency $0\%\leq\eta\leq100\%$ and a false count probability $\varepsilon\geq0$. This allows us to retrodict the number of photons that we had at the input in the least unbiased way possible. We conclude our work with some examp...
Uploads