Effects of Metal Absorber Thermal Conductivity on Clear Plastic Laser Transmission Welding

In our previous study, metals have been used as absorbers in the clear plastic laser transmission welding. The effects of metal thermal conductivity on the welding quality are investigated in the present work. Four metals with distinctly different thermal conductivities, i.e., titanium, nickel, molybdenum, and copper, are selected as light absorbers. The lap welding is conducted with an 808 nm diode laser and simulation experiments are also conducted. Nickel electroplating test is carried out to minimize the side-effects from different light absorptivities of different metals. The results show that the welding with an absorber of higher thermal conductivity can accommodate higher laser input power before smoking, which produces a wider and stronger welding seam.The positive role of the higher thermal conductivity can be attributed to the fact that a desirable thermal field distribution for the molecular diffusion and entanglement is produced from the case with a high thermal conductivity.

52 m/9 Gb/s PAM4 plastic optical fiber-underwater wireless laser transmission convergence with a laser beam reducer

A 52 m/9 Gb/s four-level pulse amplitude modulation（PAM4） plastic optical fiber（POF）-underwater wireless laser transmission（UWLT） convergence with a laser beam reducer is proposed. A 52 m/9 Gb/s PAM4 POFUWLT convergence is practically demonstrated with the application of a laser beam reducer to reduce the collimated beam diameter. A 50 m graded-index（GI）-POF is employed as an underwater extender to efficiently enhance the coverage of UWLT. The performances of PAM4 POF-UWLT convergence in view of bit error rate（BER） and eye diagrams improve with the decrease of the collimated beam diameter because of the small amount of light absorbed by clear ocean water. Competent BER and eye diagrams（three independent eye diagrams） are achieved over a 50 m GI-POF transmission with a 2 m clear ocean water link.

Remote electric powering by germanium photovoltaic conversion of an Erbium-fiber laser beam

The commercially available 4000-Watt continuous-wave(CW)Erbium-doped-fiber laser,emitting at the 1567-nm wavelength where the atmosphere has high transmission,provides an opportunity for harvesting electric power at remote“off the grid”locations using a multi-module photovoltaic(PV)“receiver”panel.This paper proposes a 32-element monocrystalline thick-layer Germanium PV panel for efficient harvesting of a collimated 1.13-m-diam beam.The 0.78-m^(2) PV panel is constructed from commercial Ge wafers.For incident CW laser-beam power in the 4000 to 10,000 W range,our thermal,electrical,and infrared simulations predict 660 to 1510 Watts of electrical output at the panel temperatures of 350 to 423 K.

Optical resonance with subwavelength spectral coherence switch in open-end cavity

The physical properties of light fields at the subwavelength scale have emerged as extensively pursued objectives in nano-optics,photonics,and plasmonics.Here,we report that in the paraxial regime,the spectral density and the spectral axial coherence(z-coherence)structures in a submicron range can be generated by employing a light beam with a suitably chosen spatial coherence state in a counter-propagating configuration,in an open-end cavity.It is established that while the spectral density forms an optical standing wave,the z-coherence state depends on the symmetry of the selected point pair and in particular,the phenomenon termed as periodical coherence switch is found.Our findings shed new light on the discussion of the role of spatial coherence in the photonic cavities,possibly inspiring further studies in the field of enhanced light-nanomaterials interactions by optical cavity.This provides a versatile framework for tailoring coherence in subwavelength space with promising applications in metrology and imaging.