Controlling the light wavefront through a scattering medium based on direct digital frequency synthesis technology

Phase modulation is a crucial step when the frequency-based wavefront optimization technique is exploited to measure the optical transmission matrix(TM) of a scattering medium. We report a simple but powerful method, direct digital frequency synthesis(DDS) technology to modulate the phase front of the laser and measure the TM. By judiciously modulating the phase front of a He–Ne laser beam, we experimentally generate a high quality focus at any targeted location through a 2 mm thick 120 grit ground glass diffuser, which is commercially used in laser display and laser holographic display for improving brightness uniformity and reducing speckle. The signal to noise ratio(SNR) of the clear round focus is 50 and the size is about 44 μm. Our study will open up new avenues for enhancing light energy delivery to the optical engine in laser TV to lower the power consumption, phase compensation to reduce the speckle noise, and controlling the lasing threshold in random lasers.

Near-Field Wireless Power Transfer, Sensing and Communication with Bessel Beams

The Bessel beam,characterized by its unique non-diffracting properties,holds promising applications.In this paper,we provide a detailed introduction and investigation into the theory and research of the Bessel beam,with a special focus on its generation and applications in the near-field region.We provide an introduction to the concepts,properties,and foundational theories of the Bessel beam.Additionally,the current study on generating Bessel beams and their applications is categorized and discussed,and potential research challenges are proposed in this paper.This review serves as a solid foundation for researchers to understand the concept of the Bessel beam and explore its potential applications.

Experimental Investigation on Finishing Technology by Magnetostrictive Ultrasonic Vibration of Magnetic Liquid

Magnetic liquid can produce alternative internal pressure under the alternative high-frequency gradient magnetic field.Because it has higher bulk modulus,the internal pressure results in its volume change.Using piezoelectric transducers,the ultrasonic wave generated by the vibration of magnetic liquids can be detected,which shows that the magnetic liquids have the magnetostrictive effect and can generate the ultrasonic vibration under the alternative magnetic gradient field.Some nonmagnetic abrasives and rust-proofing agents can be mixed into the magnetic liquids,under the alternative magnetic field,the abrasives held by magnetic liquids grind the surface of the workpieces,and thus,the finishing for the surface with complex shape,mold cavity and inner wall of tiny tubes can be realized.

In-situ Fabricated TiB_2 Particle-whisker Synergistically Toughened Ti(C,N)-based Ceramic Cutting Tool Material

The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers.However,the process of adding whiskers or nanoparticles has the disadvantages of high cost and health hazard as well as the agglomeration;although a new in-situ two-step sintering process can solve the above problems to some extent,yet the problems of low conversion ratio of the raw materials and the abnormal grain growth exist in this process.In this paper,an in-situ one-step synthesis technology is proposed,which means the growth of whiskers or nanoparticles and the sintering of the compact can be accomplished by one time in furnace.A kind of Ti（C,N）-based ceramic cutting tool material synergistically toughened by TiB_2 particles and whiskers is fabricated with this new process.The phase compositions,relationships between microstructure and mechanical properties as well as the toughening mechanisms are analyzed by means of X-ray diffraction（XRD）and scanning electron microscopy（SEM）.The composite which is sintered under a pressure of 32 MPa at a temperature of 1700℃in vacuum holding for 60 min can get the optimal mechanical properties.Its flexural strength,fracture toughness and Vickers hardness are 540 MPa,7.81 MPa·m（1/2）and 20.42 GPa,respectively.The composite has relatively high density,and the in-situ synthesized TiB_2 whiskers have good surface integrity,which is beneficial for the improvement of the fracture toughness.It is concluded that the main toughening mechanisms of the present composite are whiskers pulling-out and crack deflection induced by whiskers,crack bridging by whiskers/particles and multi-scale particles synergistically toughening.This study proposes an in-situ one-step synthesis technology which can be well used for fabricating particles and whiskers synergistically toughened ceramic tool materials.