The growing need for accurate optical simulations is central to bridging real and virtual worlds. However, current simulations are either slow or accuracy-limited. Here, we utilize our cloud-GPU-based architecture to show beyond 100-fold run-time acceleration.
The plasma mirror (PM) is an ideal model system to study relativistic optics; its geometry is simple, and its dynamics is rich and non-linear. Emphasized by high-order harmonic generation (HHG), relativistic PMs are a promising next-generation EUV source, unbounded in brightness and band-width. The applicability of these sources, however, is impeded at present because of the stringent requirement on laser intensity and temporal contrast. To-date, PM-HHG at the relativistic regime are only generated using post-compression contrast enhancement, commonly in the form of a PM-optical-switch. The complexity and low efficiency of this approach impose even stronger requirement on laser peak-power.
I will present our progress towards PM-HHG in the relativistic regime using the newly commissioned 20 TW laser system at Tel-Aviv University. The laser’s architecture is based on Picosecond Optical Parametric Chirped Pulse Amplification (Ps-OPCPA) for most of the system gain, followed by a traditional Ti:Sapphire power amplifier. In Ps-OPCPA the seed pulse is amplified in a picosecond window, enhancing contrast and eliminating pre-pulses associated with the use of classic regenerative amplifiers. These result in temporal laser contrast better than 1010 on 50 picosecond time scale.
Owing to this pristine contrast, we demonstrated PM-HHG directly without post-compression contrast enhancement.
I will present our method for controlling the spatial phase properties of the harmonics by tailoring the focused laser intensity profile. This method is based on a beam shaping technique which employs a two-optical-paths mirror that adds a half-cycle phase to the center of the beam. A variable aperture controls the fraction of laser energy outside the phase-shifted region. By changing the aperture diameter, the focal spot profile can be manipulated from gaussian to flat-top to donut shape. Owing to strong correlation between laser intensity and HHG phase, the tailored intensity profile is mapped into the HHG spatial phase profile, changing the far field properties of the EUV beam. Our aim is to minimize the angular divergence of the generated harmonics, forming the next step towards making these sources applicable. Preliminary results towards this goal will be presented.
Here we report on an optical delay device for high-power laser, with a temporal range of 0-90 nanoseconds. The device is intended for studies of laser-electron acceleration using the exploding foil method. A compact 3D mounted optical design is implemented, which enables performance at a high repeatability and low beam- distortion.
In the past two decades, ultrashort pulse lasers oscillators and amplifiers became common equipment in the fundamental scientific exploration as well as in handful of industrial applications. Those sources, which by their nature are broadband and coherent, allow exploring processes and dynamics in nature at ultrafast time scale. Due to the extremely high peak power, nonlinear optics in the ultrashort regime results in efficient frequency conversion generation processes. Among the various nonlinear conversion processes, three wave mixing and especially second harmonic generation (SHG) became widely used. Yet, frequency conversion in the ultrashort regime usually exhibits a tradeoff between the conversion bandwidth and the conversion efficiency due to the phase mismatch between the interacting waves. In the last decade, adiabatic frequency conversion method has overcome the tradeoff between conversion efficiency and bandwidth for sum frequency generation, difference frequency generation, Optical parametric amplification and recently in SHG processes. Here, we experimentally demonstrate that an adiabatic design is capable of extremely robust and efficient SHG at power levels characteristic of high-rep-rate femtosecond oscillators. We show that with pulse peak energies of nJ, one can achieve above 50% of energy conversion efficiency for 70fs Ti-Sapphire pulses. Furthermore, the flat conversion response of the presented design allows performing broadband pulse shaping manipulations before the nonlinear optical conversion. More specifically, using a spatial light modulator in a 4-f configuration, we present a tunable pump-probe based on a varying spectral phase profile in the frequency domain. Additionally, we show that by applying a π-step spectral phase, coherent control of the SHG spectrum can be achieved.
Over the recent years, van der Waals (vdW) materials, a class of materials composed of weakly bound two-dimensional (2D), atomically thin, crystalline layers, have attracted great interest due to their ability to deeply confine light and therefore significantly enhance its interaction with matter. This interaction is embodied in coupled states between light and the polarization of the media, polaritons. The most studied type of polaritons, plasmon polariton, stems from the collective oscillations of conduction electrons. These, however, suffer great losses and therefore offer limited applications. Recently, among the several other types of polaritons supported by vdW materials, the exciton polariton (EP) has stimulated intense research efforts because it can sustain both strong light– matter interactions and long-distance propagation that is necessary for applications associated with energy harvesting or information manipulation and transfer. In this context, WSe2 is of particular interest for integrated applications since it supports EP modes in the Visible- Near Infrared (VIS-NIR) spectral region at room temperature due to its tightly bond excitonic state. In the quest to unravel the underlying physics, scanning near field optical microscope (SNOM) has provided valuable insights on the nature of the steady state EP modes sustained in vdW and in WSe2 in particular. However the dynamics of the EP formation, happening in the first few hundreds of femtoseconds subsequent to light absorption, remains largely unexplored. Here we employ a unique broadband ultrafast near-field pump-probe imaging method and observe for the first time, at femtosecond and nanometric spatiotemporal scale, the dynamics of the EP waves generation and propagation in WSe2 waveguides. Our observations suggest an important interplay between the waveguide EP mode and the tip-supported plasmon. Morever, we observe an intriguing ultrafast change in the EP waveguiding properties of the WSe2 waveguides happening in the first few hundreds of femtoseconds of the EP wave formation. Our method paves the way to in-situ ultrafast coherent control of EPs modes in vdW materials.
In this article we present preliminary results for the combination of two interesting fields in the last few years: 1) Compressed imaging (CI), which is a joint sensing and compressing process, that attempts to exploit the large redundancy in typical images in order to capture fewer samples than usual. 2) Millimeter Waves (MMW) imaging. MMW based imaging systems are required for a large variety of applications in many growing fields such as medical treatments, homeland security, concealed weapon detection, and space technology. Moreover, the possibility to create a reliable imaging in low visibility conditions such as heavy cloud, smoke, fog and sandstorms in the MMW region, generate high interest from military groups in order to be ready for new combat. The lack of inexpensive room temperature imaging sensors makes it difficult to provide a suitable MMW system for many of the above applications. A system based on Glow Discharge Detector (GDD) Focal Plane Arrays (FPA) can be very efficient in real time imaging with significant results. The GDD is located in free space and it can detect MMW radiation almost isotropically. In this article, we present a new approach of reconstruction MMW imaging by rotation scanning of the target. The Collection process here, based on Radon projections allows implementation of the compressive sensing principles into the MMW region. Feasibility of concept was obtained as radon line imaging results. MMW imaging results with our resent sensor are also presented for the first time. The multiplexing frame rate of 16×16 GDD FPA permits real time video rate imaging of 30 frames per second and comprehensive 3D MMW imaging. It uses commercial GDD lamps with 3mm diameter, Ne indicator lamps as pixel detectors. Combination of these two fields should make significant improvement in MMW region imaging research, and new various of possibilities in compressing sensing technique.
Millimeter (mm)and sub-mm wavelengths or terahertz (THz) band have several properties that motivate their use in imaging for security applications such as recognition of hidden objects, dangerous materials, aerosols, imaging through walls as in hostage situations, and also in bad weather conditions. There is no known ionization hazard for biological tissue, and atmospheric degradation of THz radiation is relatively low for practical imaging distances. We recently developed a new technology for the detection of THz radiation. This technology is based on very inexpensive plasma neon indicator lamps, also known as Glow Discharge Detector (GDD), that can be used as very sensitive THz radiation detectors. Using them, we designed and constructed a Focal Plane Array (FPA) and obtained recognizable2-dimensional THz images of both dielectric and metallic objects. Using THz wave it is shown here that even concealed weapons made of dielectric material can be detected. An example is an image of a knife concealed inside a leather bag and also under heavy clothing. Three-dimensional imaging using radar methods can enhance those images since it can allow the isolation of the concealed objects from the body and environmental clutter such as nearby furniture or other people. The GDDs enable direct heterodyning between the electric field of the target signal and the reference signal eliminating the requirement for expensive mixers, sources, and Low Noise Amplifiers (LNAs).We expanded the ability of the FPA so that we are able to obtain recognizable 2-dimensional THz images in real time. We show here that the THz detection of objects in three dimensions, using FMCW principles is also applicable in real time. This imaging system is also shown here to be capable of imaging objects from distances allowing standoff detection of suspicious objects and humans from large distances.
In recent years, much effort has been invested to develop inexpensive but sensitive Millimeter Wave (MMW) detectors
that can be used in focal plane arrays (FPAs), in order to implement real time MMW imaging. Real time MMW imaging
systems are required for many varied applications in many fields as homeland security, medicine, communications,
military products and space technology. It is mainly because this radiation has high penetration and good navigability
through dust storm, fog, heavy rain, dielectric materials, biological tissue, and diverse materials. Moreover, the
atmospheric attenuation in this range of the spectrum is relatively low and the scattering is also low compared to NIR
and VIS. The lack of inexpensive room temperature imaging systems makes it difficult to provide a suitable MMW
system for many of the above applications. In last few years we advanced in research and development of sensors using
very inexpensive (30-50 cents) Glow Discharge Detector (GDD) plasma indicator lamps as MMW detectors. This paper
presents three kinds of GDD sensor based lamp Focal Plane Arrays (FPA). Those three kinds of cameras are different in
the number of detectors, scanning operation, and detection method. The 1st and 2nd generations are 8 × 8 pixel array and
an 18 × 2 mono-rail scanner array respectively, both of them for direct detection and limited to fixed imaging. The last
designed sensor is a multiplexing frame rate of 16x16 GDD FPA. It permits real time video rate imaging of 30 frames/
sec and comprehensive 3D MMW imaging. The principle of detection in this sensor is a frequency modulated
continuous wave (FMCW) system while each of the 16 GDD pixel lines is sampled simultaneously. Direct detection is
also possible and can be done with a friendly user interface. This FPA sensor is built over 256 commercial GDD lamps
with 3 mm diameter International Light, Inc., Peabody, MA model 527 Ne indicator lamps as pixel detectors. All three
sensors are fully supported by software Graphical Unit Interface (GUI). They were tested and characterized through
different kinds of optical systems for imaging applications, super resolution, and calibration methods. Capability of the
16x16 sensor is to employ a chirp radar like method to produced depth and reflectance information in the image. This
enables 3-D MMW imaging in real time with video frame rate. In this work we demonstrate different kinds of optical
imaging systems. Those systems have capability of 3-D imaging for short range and longer distances to at least 10-20
meters.
Imaging systems in millimeter waves are required for applications in medicine, communications, homeland security, and space technology. This is because there is no known ionization hazard for biological tissue, and atmospheric attenuation in this range of the spectrum is low compared to that of infrared and optical rays. The lack of an inexpensive room temperature detector makes it difficult to give a suitable real time implement for the above applications. A 3D MMW imaging system based on chirp radar was studied previously using a scanning imaging system of a single detector. The system presented here proposes to employ a chirp radar method with Glow Discharge Detector (GDD) Focal Plane Array (FPA of plasma based detectors) using heterodyne detection. The intensity at each pixel in the GDD FPA yields the usual 2D image. The value of the I-F frequency yields the range information at each pixel. This will enable 3D MMW imaging. In this work we experimentally demonstrate the feasibility of implementing an imaging system based on radar principles and FPA of inexpensive detectors. This imaging system is shown to be capable of imaging objects from distances of at least 10 meters.
A miniature neon indicator lamp, also known as a Glow Discharge Detector (GDD), costing about 50 cents, was found to be an excellent room temperature THz radiation detector. Polarization effects on heterodyne detection were investigated in this work. In heterodyne detection, because of the dot product relationship between signal electric field (ES) and local oscillator (LO) electric field (Elo), optimal operation of heterodyne detection is obtained when ES and Elo are of the same polarization. Preliminary results at 300 GHz showed better sensitivity by a factor of 20 with only 56 microwatt local oscillator power using heterodyne compared to direct detection. Further improvement of the detection sensitivity can be achieved if the LO power (Plo) is increased. In this work investigation of polarization effects in heterodyne detection using neon indicator lamp GDD was carried-out. Experimental results of heterodyne detection at 300 GHz showed that an intermediate frequency (IF) signal was obtained for orthogonal polarization of the LO and signal, in contradiction to the theory. Also, our latest imaging results using Glow Discharge Detector at millimeter wavelengths will be shown in this work.
Millimeter wave (MMW) imaging systems are required for applications in medicine, communications, homeland security, and space technology. This is because there is no known ionization hazard for biological tissue, and atmospheric attenuation in this range of the spectrum is relatively low. The lack of inexpensive room temperature imaging systems makes it difficult to give a suitable MMW system for many of the above applications. 3D MMW imaging system based on chirp radar was studied previously using a scanning imaging system of a single detector. The system presented here proposes to employ a chirp radar method with a Glow Discharge Detector (GDD) Focal Plane Array (FPA) of plasma based detectors. Each point on the object corresponds to a point in the image and includes the distance information. This will enable 3D MMW imaging. The radar system requires that the millimeter wave detector (GDD) will be able to operate as a heterodyne detector. Since the source of radiation is a frequency modulated continuous wave (FMCW), the detected signal as a result of heterodyne detection gives the object's depth information according to value of difference frequency, in addition to the reflectance of the image. In this work we experimentally demonstrate the feasibility of implementing an imaging system based on radar principles and FPA of GDD devices. This imaging system is shown to be capable of imaging objects from distances of at least 10 meters.
In recent years, much effort has been invested to develop room temperature inexpensive, but sensitive, millimeter wave (MMW) and terahertz (THz) detectors that can be used as pixels in focal plane arrays, which is important for real-time imaging. A new 18×2 neon indicator lamp MMW/THz scanner was developed. The components of the camera include horizontally shifted two-column glow discharge detectors in a scanning array. The detectors, costing about 50 cents each, are wired to a preprocessing card, a VLSI board, and a motor for scanner movement. A description of the VLSI Verilog programmable hardware of the new scanner, the physical architecture, the software user interface, and imaging results at 97 GHz are presented. At this stage, the emphasis is focused on the lamp exposure time and spatial resolution when the scanning is performed horizontally. In the future it is planned to expose all pixels simultaneously for real-time imaging. New software capabilities allow the application of digital image enhancement algorithms. Fast scanning permits obtaining images in 1 to 5 s. Oversampling yields a sharper edge response and a higher signal-to-noise ratio.
A miniature neon indicator lamp, also known as a Glow Discharge Detector (GDD), costing about 50 cents, was
found to be an excellent room temperature THz radiation detector. A proof of concept of 300 GHz heterodyne
detection using GDD is demonstrated in this paper. Furthermore, a comparison to direct detection was carried-out and
polarization effects on heterodyne detection were investigated. Preliminary results at 300 GHz showed better
sensitivity by a factor of 20 with only 56 microwatt local oscillator power using heterodyne compared to direct
detection. Further improvement of the detection sensitivity can be achieved if the Local Oscillator (LO) power (Plo) is
increased. Effects of orthogonal polarizations of signal and local oscillator powers on heterodyne sensitivity were
found to be surprisingly weak. More efficient quasi optical design for heterodyne detection is presented in this study,
experimental results showed above 50% better performance compared to conventional ones.
The properties of terahertz (THz) radiation are well known. They penetrate well most non-conducting
media; there are no known biological hazards, and atmospheric attenuation and scattering is lower than visual
and IR radiation. Thus THz imaging is very attractive for homeland security, biological, space, and industrial
applications. In the other hand, the resolution of MMW images is lower comparing to IR and visual due to
longer wavelength. Furthermore, the diffraction effects are more noticeable in THz and MMW imaging
systems. Thus the MMW images are blurred and unclear and thus it is difficult to see the details and small
objects. In recent experimental work with 8X8 Glow Discharge Detector (GDD) Focal Plane Array (FPA) we
were able to improve the resolution of MMW images by using oversampling methods with basic DSP
algorithms.
In this work a super resolution method with basic DSP algorithms will be demonstrated using the
2X18 double row camera. MMW images with sub wavelength resolution will be shown using those methods
and small details and small objects will be observed.
Terahertz (THz) radiation or millimeter wavelength detection and imaging don't have to be expensive. A miniature neon
indicator lamp costing about 50 cents acting as a Glow Discharge Detector (GDD) is excellent as a low cost THz
detector, but not as the most sensitive detector on the market. Experimental results show that a GDD can work as
heterodyne detector, which improves the sensitivity. The experimental results show that sensitivity of heterodyne
detection is improved by two orders of magnitude as compared to direct detection. We show here a proof of concept at
low frequencies. In this work we compare the performance of GDDs in direct detection to the performance of GDDs in
heterodyne detection at 10 GHz and at 300GHz with a low power source.
KEYWORDS: Terahertz radiation, Super resolution, Sensors, Digital signal processing, Point spread functions, Staring arrays, Modulation transfer functions, Imaging systems, Metals, Lamps
The properties of terahertz (THz) radiation are well known. They penetrate well most non-conducting media; there
are no known biological hazards, and atmospheric attenuation and scattering is lower than visual and IR radiation. Thus
THz imaging is very attractive for homeland security, biological, space, and industrial applications
Recently we have found experimentally that inexpensive miniature neon indicator lamp Glow Discharge Detectors
(GDD) can be used as THz detectors. Based on the GDD we designed, constructed, and experimentally tested an 8×8
GDD array. In order to improve the performance and the resolution of the THz images a larger array is required. In this
work we use a special double row 2×18 moving array detector. The 2×18 GDD array enables us to employ scanning
method in order to obtain 36×36 pixel THz images. Furthermore, using this double row array it will be possible to
employ super resolution methods. Optical properties such as optical transfer function and measurement of point spread
function are presented, as well as first results for the 2×18 GDD array.
Development of focal plane arrays (FPA) for mm wavelength and THz radiation is presented in this paper. The FPA is
based upon inexpensive neon indicator lamp Glow Discharge Detectors (GDDs) that serve as pixels in the FPA. It was
shown in previous investigations that inexpensive neon indicator lamps GDDs are quite sensitive to mm wavelength and
THz radiation. The diameter of GDD lamps are typically 3-6 mm and thus the FPA can be diffraction limited.
Development of an FPA using such devices as detectors is advantageous since the costs of such a lamp is around 30-50
cents per lamp, and it is a room temperature detector sufficiently fast for video frame rates. Recently a new 8×8 GDD
FPA VLSI board was designed, constructed, and experimentally tested. First THz images as well as DSP methods using
this GDD FPA are demonstrated. Super resolution was achieved by moving the 8×8 pixel board appropriately in the
image plane so that 32X32 pixel images are also obtained and shown here, with much improved image quality because
of much reduced pixelization distortion.
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