Order Harmonic Field Research Articles

Space‐Time Coding Metasurface For Multifunctional Holographic Imaging

AbstractHolographic imaging as one of promising image techniques reconstructs object image using the amplitude and phase information scattered from objects. Programmable metasurface composed of digitally coding unit cells can arbitrarily manipulate amplitude and phase of the scattering wave by tailoring operation states of the unit cells, and thus achieves high‐resolution imaging reconstruction. However, the conventional metasurface can only achieves a desired holographic image on an imaging plane. This paper presented a time‐space coding 2‐bit metasurface to overcome this challenge. By rapidly switching PIN diodes loaded in metasurface unit cell according to the customized time sequences, the magnitude and phase of the ±1st order harmonic fields can be fully controlled, achieving the hologram imaging at the higher order harmonics. The proof‐of‐concept measurements are given to demonstrate the versatile holographic imaging functions at the ±1st order harmonics including two different holographic images on an imaging plane, holographic imaging and beam scanning, and holographic imaging and orbital angular momentum (OAM) wave generation, which undoubtedly enriches the applications of the programmable metasurfaces in the field of the holographic imaging.

Brilliant gamma-ray beam and electron\u2013positron pair production by enhanced attosecond pulses

Electron–positron pair production via Breit–Wheeler process requires laser intensities approaching 1024 W cm−2 due to the small cross-section. Here, we propose a mechanism for brilliant γ-ray emission and dense GeV pairs creation accompanied with high-harmonic generation by using plasma mirror and an ultra short pulse with the intensity of 3 × 1023 W cm−2. The laser is reflected by the solid surface after propagating tens of microns in a near-critical density plasma and breaks into short wave packets. The intensity of the reflected high order harmonic field is enhanced by the focusing and compression effects from the deformed oscillating mirror. The radiation trapped electrons emit γ-photons while colliding with the reflected attosecond pulses. The peak intensity of the γ-ray reaches 0.74 PW with the brilliance of 2 × 1024 s−1 mm−2 mrad−2 (0.1%BW)−1 (at 58 MeV). A GeV positron beam is obtained with density of 4 × 1021 cm−3 and a particle number of 5.6 × 109.

Design Optimization of the New D1 Dipole for HL-LHC Upgrade

The High-Luminosity Large Hadron Collider upgrade (LHC) project aims to increase the peak luminosity of the LHC to 5 ×1034 cm - 2s - 1, and a total integrated luminosity of 3000 fb - 1 from 2020 to 2030 by upgrading the low-beta insertion system for the ATLAS and CMS experiments. The aperture of the insertion magnets including the focusing/defocusing quadrupoles and separation dipoles will be doubled to achieve a smaller β*. This paper presents the latest design updates of the separation dipole D1 magnet, including the study of the different cable types to vary the main field; the modifications of the iron shape for the new design options to minimize the iron saturation effect on field quality; and the optimization of the coil ends to reduce the peak field and higher order harmonic field integrals in the ends.

Pulse propagation in an elastic medium with quadratic nonlinearity (L)

This letter examines the propagation of an acoustic pulse in an elastic medium with weak quadratic nonlinearity. Both a displacement pulse and a stress pulse of arbitrary shapes are used to generate the wave motion in the solid. By obtaining the explicit solutions for arbitrary pulse shapes, it is shown that for a sinusoidal tone-burst, in addition to a second order harmonic field, a radiation induced static strain field is also generated. These results help clarify some confusion in the recent literature regarding the shape of the propagating static displacement pulse.

Interferometry of an attosecond pulse train generated from Xe gas target

We have demonstrated the interferometry of extreme ultraviolet (XUV) high-order harmonic fields of femtosecond Ti:sapphire laser pulses generated from the Xe gas target. We describe how we have measured the spatio-spectral fringes with an XUV spectrograph and extracted the interference traces from the measured spectrograms in detail. The comb-like structure in the spectrum ranging from the 11th to 17th order harmonic fields exhibits the periodical recurrence of interference fringes as an attosecond pulse train.

A Wireless, Passive Chemo-Mechanical Glucose Sensor

A wireless, passive chemo-mechanical sensor was developed for glucose monitoring. The sensor consisted of an airtight chamber split into two compartments by a glucose-permeable membrane. The lower compartment was a flow chamber for the test liquid to pass through, and the upper compartment was a circular drum with the glucose-permeable membrane at the bottom and a soft silicone rubber membrane on top. A permanent magnetic strip (biasing element) and a magnetically soft strip (sensing element) were attached to the soft rubber membrane and a polycarbonate block suspended over the rubber membrane, respectively. A magnetic AC field and a DC field were applied to the sensing element to generate higher order harmonic fields that were remotely measured with a detection coil. To measure glucose concentration, the permeable membrane was coated with glucose oxidase (GOD) enzyme. When glucose flowed through the lower chamber, it seeped through the membrane to the the upper compartment and interacted with the GOD enzyme and consumed oxygen. This caused a pressure drop in upper compartment that pulled the soft rubber membrane inward, changing the separation distance between the two magnetic elements and shifting the higher order harmonic fields. The advantages of this sensor platform include its simplistic design, low cost, as well as its wireless and passive nature. Although this technology was only applied for glucose monitoring, it could be used for other chemicals with the proper enzyme or catalyst coating on the permeable membrane.

A Wireless Embedded Sensor based on Magnetic Higher-order Harmonic Fields: Application to Liquid Pressure Monitoring.

A wireless sensor based on the magnetoelastic, magnetically soft ferromagnetic alloy was constructed for remote measurement of pressure in flowing fluids. The pressure sensor was a rectangular strip of ferromagnetic alloy Fe(40)Ni(38)Mo(4)B(18) adhered on a solid polycarbonate substrate and protected by a thin polycarbonate film. Upon excitation of a time-varying magnetic field through an excitation coil, the magnetically soft sensor magnetized and produced higher-order harmonic fields, which were detected through a detection coil. Under varying pressures, the sensor's magnetoelastic property caused a change in its magnetization, altering the amplitudes of the higher-order harmonic fields. A theoretical model was developed to describe the effect of pressure on the sensor's higher order harmonic fields. Experimental observations showed the 2(nd) order harmonic field generated by the pressure sensor was correlated to the surrounding fluid pressure, consistent with the theoretical results. Furthermore, it was demonstrated that the sensor exhibited good repeatability and stability with minimal drift. Sensors with smaller dimensions were shown to have greater sensitivity but lower pressure range as compared to their larger counterparts. Since the sensor signal was also dependent on the location of the sensor with respect to the excitation/detection coil, a calibration algorithm was developed to eliminate signal variations due to the changing sensor location. Because of its wireless and passive nature, this sensor is useful for continuous and long-term monitoring of pressure at inaccessible areas. For example, sensors with these capabilities are suitable to be used in biomedical applications where permanent implantation and long-term monitoring are needed.

A Remote Query Pressure Sensor Based on Magnetic Higher Order Harmonic Fields

The design and fabrication of a wireless, passive pressure sensor based on the change in magnetic higher order harmonic fields is described. The sensor was made of an airtight pressure chamber with two opposite membranes: a rigid membrane attached to a magnetically soft ferromagnetic strip (sensing element) and a flexible membrane attached to a permanent magnetic strip (biasing element). The flexible membrane of the chamber deflected with changing pressure, thus varying the separation distance between the sensing and biasing elements. The change in separation distance in turn altered the biasing field experienced by the sensing element, varying the pattern of its magnetic higher order harmonic fields allowing remote pressure monitoring through a magnetic coil. In this work, different materials were used to fabricate the flexible membranes for sensors of different dynamic ranges. Experimental results showed the shifts in magnetic higher order harmonic fields were linear for all sensors, but with different sensitivity depending on the elasticity of the flexible membrane. The novelty of this sensor is its wireless, passive nature, which is ideal for applications where wire connections are prohibited. In addition, the simple sensor design reduces cost, allowing disposable use. Potential applications of such a sensor technology include long-term structural monitoring (concrete, asphalt) and in vivo pressure monitoring inside the human body.