Electromagnetic radiation is attenuated by a metal grid disposed on a substrate. The magnitude of extinction is a
combination of the total scattering and surface plasmon absorption, as predicted by the Mie theory adapted to the case at
hand. Experimental measurements conducted over a wide wavelength range using a metal grid on a sapphire window
support the calculations. We analyzed the electric field generated in the wire mesh by the Drude-Lorentz theory. While
the analysis and data show that the attenuation across a window covered by a wire mesh consists of a combination of the
Fresnel and Mie losses, a considerable plasmon field is generated in the wire. Further it is shown that under visible
illumination the metal grid generates enough electrical filed to substantially elevate the window temperature.
Flux of electromagnetic radiation is attenuated on propagation through a metal grid disposed on a substrate. The
magnitude of extinction is a combination of the total scattering and surface plasmon absorption, which is predicted by
the Mie theory adapted to the case at hand. Experimental measurements over a wide wavelength range conducted using a
metal grid on a sapphire window support the calculations. Further analyzed is the electric field generated in the wire
mesh, treated by the Drude-Lorentz theory. While the analysis and data show that the attenuation across a window
covered by a wire mesh is consists of a combination of the Fresnel and Mie losses, a considerable plasmon field is
generated in the wire.
Analyzed are thermally induced aberrations in optical beams propagating through solid-state
laser media. Several geometrical configurations are considered: cylindrical rod, thin disk and slab.
Predicted are thermally-induced optical effects in the temperature range of 77 - 770K. The analysis
is based on an analytical solution to the problems of nonlinear heat transfer and material stressstrain
field. Predictions are made for the temperature field, stress distribution, refractive index
profile, ray trajectories, focal lengths, beam phases and aberrations. Most optimistic results are
obtained for thin disk configuration in which the disk is attached to a heatsink and to a conducting
cap on either facet.
The objective of this work is the suppression of speckles in an image illuminated by a
remote laser. This is accomplished by a novel method in which the illuminating laser
beam propagates through a multimode fiber dithered at an arbitrary section, then passes
through a microlens array prior to illuminating the image generator. Thereby the speckle
contrast is reduced to its minimum value for dithering frequencies of at least 25 Hz,
attaining a magnitude speckle contrast of less than 12%, and illumination homogeneity
across the illumination filed of less than 20%.
The objective of this work is the suppression of speckles in an image illuminated by a remote laser.
This is accomplished by a novel method in which the illuminating laser beam propagates through a
multimode fiber dithered at an arbitrary section, then passes through a microlens array prior to
illuminating the image generator. Thereby the speckle contrast is reduced to its minimum value for
dithering frequencies of at least 25 Hz, attaining a magnitude speckle contrast of less than 12%, and
illumination homogeneity across the illumination filed of less than 20%.
Antireflective (AR) coating on waveguides with high refractive index is imperative to minimize insertion losses. In fabricating silicon, rectangular, suspended waveguides on silicon-on-insulator (SOI) wafers, a single Si3N4 layer is deposited on the waveguide walls. For the purpose of applying an optimum layer, we develop an integrated micromechanical gauge to determine the coating width by measuring the induced stress in the silicon. Gauges at different sites on a wafer produce results with a standard deviation of about 0.5%. The insertion loss due to the waveguides is measured directly by coupling a laser beam at 1550 nm from a single-mode fiber to the waveguide, then to another fiber and a detector. Tests are run on six wafers and two types of devices: a waveguide with two facets and a waveguide with a gap, presenting four facets. The optimal silicon-nitride thickness is found at 200 nm, featuring a fiber-waveguide-fiber insertion loss of about 1 dB for a two-facet device and 1.7 dB for a four-facet device.
We present a simple analytical solution for singly resonant OPO. The present analysis permits calculating the depletion efficiency of the OPO even when the resonated signal suffers from strong intracavity losses. To the best of our knowledge, this is the first model, which yields an analytical formula in the depleted signal case. The model can be a useful tool to design cavity mirror reflectivity for a given pump intensity and intracavity losses.
We report the development of a high-power Er:strengthened- glass laser emitting at the eye-safe 1.535 μm wavelength. The flashlamp pumped Cr:Yb:Er:glass produced 330 mJ output @ 0.45% slope efficiency. Thermo-optical measurements indicated strong thermal lensing, of 16 diopter/kW and mild birefringence induced depolarization of 5% at 200 W. In terms of radial and birefringence elastooptical coefficients these data determine the values of 0.075 ± 0.002 and 0.0094, respectively. For a hemispherical resonator configuration a TEM00 beam was achieved.
We show a compact multi-pass amplifier, based on a single dual-rod laser-head whihc produces ultra-high gain. A double-pass produced a maximum small signal gain of 4x108. Another pass was permitted by including a specially designed Brillouin phase conjugate mirror (PCM). This enabled a total gain of 7.7x1010, which raised an input signal of 10pJ to 770mJ output signal. To the best of our knowledge this is the highest gain reported to date from any type of laser amplifier scheme. The amplification system is fairly simple in that it consists of only one dual-rod laser head and hence only a single power supply. We show that this system can be utilized for producing high-energy long temporally-smooth narrow linewidth pulses, as well as high power controllable, temporally-modulated pulses.
We are currently developing a high-speed photographic system that images objects engulfed in high radiance backgrounds. Using a copper vapor laser as a pulsed illuminator in conjunction with a narrow band interference filter and an electro-optic shutter as spectral and temporal filters respectively, the background radiance is diminished by eight orders of magnitude. Consequently, the back-scattered imaging photons from the laser overpower the radiant background, resulting in a sufficiently high imaging-to- background ratio. Such high levels of background discrimination is made possible by the copper vapor laser that illuminates within a spectral line of 7 GHz with great intensity centered on the 1 nm vapor laser that illuminates within a spectral line of 7 GHz with great intensity centered on the 1 nm wide transmission band of the interference filter. The laser emits 30 ns pulses with a repetition rate of 20 kHz, synchronized with an equivalent open aperture period of the electro-optic shutter. The image is captured by an electronic camera at the rate of 20,000 per second. The image is available for further digital image processing.
We present a new ladar (laser radar) for the detection of objects off the line-of-sight. This is accomplished by a transceiver and a fiberoptic cable that relays an outgoing laser beam to, and a returning signal from a target. The transmission signal is a laser diode emitted beam at 1550 nm, ideal from the aspects of both eyesafety and minimum loss in a silica fiber. In our immediate application, the detection of an obstacle on the railroad track of a high-speed train, the laser pulses propagate through air and the fiberoptic cable, successively. Under a variety of simulated weather conditions and by traversing twice through a 2 km fiber, we measured a signal-to-noise of 300.
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