Electronics circuits are susceptible to production defects. Yield improvement can be obtained by in-process inspection and repair of these defects. We describe an automated laser repair system, and discuss how to optimize it to obtain best performance in terms of throughput and quality. The laser repair system can repair excess conductor defects (e.g., shorts) in printed circuit boards by an ablation process. Moreover, it includes a feedback loop by capturing images of the repaired area using a co-aligned imaging system. Here we present the automated laser system design and repair process as well as repair performance optimization.
We introduce into optical systems, susceptible to be interrupted or damaged from laser, novel passive solid-state
threshold-triggered Wideband Protection Filter (WPF) that blocks the transmission only if the power exceeds a certain
threshold. We present new protection capabilities of our latest filter composed of improved technology. The WPF can be
readily used for protection of detectors, cameras, or eye safety.
Detection of fast moving objects is challenging. Even more challenging is accurately locating them in space. We present
optical sensors that can locate fast moving objects that penetrate into virtual optical screens. Each sensor is composed of
several laser sources and detectors, and the three-dimensional mapping is based on combinations of range measurements,
triangulation and geometry.
We present a passive, solid-state threshold-triggered Wideband Protection Filter (WPF) that blocks the transmission only
if the power exceeds a certain threshold. We demonstrate the protection ability of the WPF against laser threats including
protection behavior for single and series of pulses. The WPF can be readily used for protection of detectors, cameras, or
eye safety.
Imaging and detection systems are susceptible to detector saturation or permanent damage caused by powerful light sources or high power lasers. We propose and demonstrate a passive, solid-state threshold-triggered optical protection filter. At input power below threshold, the filter has high transmission over the whole spectral band. However, when the input power exceeds the threshold power, transmission is decreased dramatically. As opposed to fixed spectral filters, which permanently block only specific wavelengths, the wideband filter is clear at all wavelengths until it is hit by damaging light. When high incident optical power impinges on the wideband filter at a certain spot, this spot becomes permanently opaque. The wideband protection filter is fast enough to block nanosecond laser pulses.
Waveguides fabricated in high-index-contrast material systems offer very strong light confinement compared to that
achieved in low-index-contrast material systems. A core layer of silicon (refractive index n~3.5) surrounded by silica
cladding (n~1.5) on a silicon-on-insulator (SOI) substrate is an example of a high-index-contrast material system. This
enables miniaturization of functional optical components and enhances dense integration of devices on waveguide chips.
Some physical effects, such as, Raman and Stimulated Brillouin Scattering (SBS) are much stronger in silicon than in
glass. In view of the above two reasons, it is possible to use short (a few centimeter long) silicon waveguides to amplify
light or modify its wavelength, instead of using kilometers of glass optical fibers.
A large mismatch between the common optical fiber dimensions and that of the high-index-contrast waveguides makes
it difficult to couple light in and out of the chip. A number of techniques have been utilized for this purpose, including
prism couplers, grating couplers, tapered fibers and micro-lens mode transformers [ 1, 2]. A better option to effectively
couple light in this situation is by incorporating a waveguide section that is tapered vertically, as well as laterally
between the fiber and the waveguide. This tapered section acts as a classic adiabatic modal transformer [ 3, 4, 5, 6] that
transforms the input fundamental mode shape to that of the waveguide mode.
In this paper, coupling losses between optical fibers and rib-loaded SOI waveguides with lateral only (1-D) and
combination of lateral and vertical (2-D) tapers are presented. The waveguide fabrication process down to 0.75 μm size
with the tapers is discussed and the measured coupling losses are compared to predictions. Measured coupling loss
values for waveguides with 2-D tapers (~1.8 dB) show a significant improvement over those for waveguides with 1-D
tapers (~4 dB) or no tapers (~8 dB), and are in excellent agreement with predictions. A qualitative analysis of the Free
Carrier Absorption (FCA) phenomenon in narrow silicon waveguides that suppresses the Raman amplification and SBS
is also shown.
The increase of DWDM wavelength channel count has resulted in significant increases in power applied in telecommunication optical fibers. As higher powers and longer distances are required, there is a need for stronger fiber amplifiers. Here we present passive components for controlling the optical power in high power networks.
High power amplifiers are used to increase the signal power injected into the input port. The output signal is a function of the input signal (including spectral and temporal shape), as well as the operating conditions of the amplifying unit.
When the input signal is composed of many wavelength channels, each having its own power level, power management (or equalization) is required at the input port. When the channels are equalized, amplifiers are exploited most efficiently. Power unbalance due to non-equalized amplification of amplifiers causes degradations of signal to noise ratio.
Output ports of fiber amplifiers are sometimes susceptible to high power spikes. This can occur, for example, when the input to an operating amplifier is suddenly turned on. These spikes can be destructive to components and equipment on the network. Moreover, phenomena known as the ‘fiber fuse’ can destroy the fibers in a network due to over-power.
We introduce novel passive optical components, which can control and regulate the optical powers in the input to and at the output from a fiber amplifier. These components include power limiters that protect against excessive optical power transmission, and power equalizers. They can either replace or complement existing active power feedback control loops.
Power control components for high power networks will be described with emphasis on both their properties and their application in the network.
The luminescence of silver bromide crystals doped with rare earth ions (Nd3+, Pr3+, and Er3+) was investigated in the visible and near infrared spectral ranges. The emission, excitation, and absorption spectra, as well as the kinetic parameter, were measured over a broad temperature range. The Judd-Ofelt analysis was applied to the rare-earth doped crystals, and transition rates, branching ratios, and quantum efficiencies were calculated. Good agreement between theory and experiment was obtained.
Theoretical modeling of strongly pumped doped silver halide fiber amplifiers is presented. This is an analytic part of an effort to introduce new lasing materials, composed of doped silver halides, in the near or mid IR region. The analysis is based on a rate equation formalism, for which experimental measurements of various optical properties of doped silver halide and crystals were applied as input parameters. The model includes solutions for both three- and four-level systems, such as Er3+ and Nd3+. Optimal range of fiber dimensions, doping materials and concentrations, and other optical properties are suggested in order to achieve significant amplification.
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