Low Diffraction Beam Research Articles

Low-diffraction beaming in plasmonic crystals

We analyze the propagation of electromagnetic modes guided by periodic plasmonic structures. We use full-wave solutions of Maxwell equations to calculate dispersion of these modes and derive analytical description of their optical properties. Finally, we demonstrate that, at a certain frequency range that can be controlled by the geometry, diffraction of these guided states is strongly suppressed, leading to formation of low-diffraction beams. A beaming phenomenon, consistent with earlier experiments, can be used as the foundation for on-chip communication or microscopy.

In-phase, coherent photonic crystal vertical-cavity surface-emitting laser arrays with low divergence

Two-dimensional vertical-cavity surface-emitting laser (VCSEL) arrays are defined using an etched photonic crystal pattern and ion implantation. The 2×2 laser arrays are shown to operate in a single in-phase mode from threshold to maximum output power. The in-phase interference between the multiple lasers constituting the array form an angularly narrow, on-axis peak in the far field. These coherently-coupled laser arrays are of interest owing to their ease of fabrication and potential for creating low-diffraction beams with increased output power.

Experimental Investigation of Polymeric Material Removal by Low Diffraction Laser Beam

Effects of improved beam quality of a low diffraction laser beam on laser material removal processes are experimentally investigated in a polymeric material. The experimental results are in agreement with theoretical predictions. The results show that the low diffraction beam has marked advantages over the Gaussian beam in ablation-dominated material removal processes in terms of larger depth and smaller taper at the same average power level.

A low diffraction laser beam as applied to polymer ablation

A low diffraction beam is obtained by altering the existing resonator of a CO2 laser using a special phase plate. The phase plate is designed based on the boundary diffraction principle and is implemented on the resonator rear mirror. It is found that the low diffraction beam has a smaller M2 value than that of a Gaussian beam. The effects of the improved beam quality on a laser ablation process are investigated using a polymeric material. A theoretical model is provided to predict the laser ablated hole profile and penetration depth. The theoretical results are in agreement with the experimental measurements. Both the experimental and theoretical results show that the low diffraction beam has marked advantages over the Gaussian beam in ablation-dominated material removal processes in terms of larger depth and smaller taper at the same average power level.

Experimental results of localized wave experiments

The theory for several low diffraction beams has been upheld by experimental verification in several tests to date. Both the modified pulse spectrum and the superposed Gaussian beams have been verified by Livermore projects in the laboratory and in open water tests. Test methods, instrumentation, data analysis techniques, and results will be discussed in this presentation. [This work was performed under the auspices of the Department of Energy by Lawrence Livermore National Laboratory under Contract W-7405-ENG-48.]

Time-frequency analysis of low diffraction beam pulses

Recent work in low diffraction beams has given our group some new sets of wave fields to investigate. Theoretical predictions matched experimental measurements closely, and several comparison techniques were included in the analysis. The field experiments have now been conducted at the NUWC Keyport facility and, most recently, at the University of Texas’ Applied Research Laboratory facility in Lake Travis. In cooperation with ARL, a series of low diffraction beam pulses was launched to a wide band width receiver 600 feet distant. Among the comparison methods used was a time-frequency analysis of the received pulse. For each angular position the frequency arrival times via time-frequency analysis are investigated. It is hoped this analysis will shed light on this very interesting phenomena.