Photonics

Compact Two-Dimensional Spectrometer Optics

This unit would feature coarse and fine resolution along two orthogonal axes. NASA’s Jet Propulsion Laboratory, Pasadena, California The figure is a simplified depiction of a proposed spectrometer optical unit that would be suitable for incorporation into a remote-sensing instrumentation system. Relative to prior spectrometer optical assemblies, this unit would be compact and simple, largely by virtue of its predominantly two-dimensional character.

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Graphite/Cyanate Ester Face Sheets for Adaptive Optics

Unlike glass face sheets, these would be nearly unbreakable. Marshall Space Flight Center, Alabama It has been proposed that thin face sheets of wide-aperture deformable mirrors in adaptive-optics systems be made from a composite material consisting of cyanate ester filled with graphite. This composite material appears to offer an attractive alternative to low-thermal-expansion glasses that are used in some conventional optics and have been considered for adaptive-optics face sheets.

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Fractal-Based Encryption

Encryption methods based upon nonprobabilistic nondeterminism show promise in the optical age. In 1987 a discovery led to the formal proof that it is possible to use chaotic functions to arrive at a nonprobabilistic and nondeterministic method normal context of the operation of this system, and by using a virtual operational environment, the investigators are manipulating data in eight dimensions, which require a sixty-four discrete coordinate system, using eight nominative octets. Each octet is further addressed using the characters 0 through 9, and lower- or upper-case letters from A to Z. These provide the ability to address using normal ASCII characters. This format was chosen to ensure backward and forward compatibility with external third-party-written software.

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Fiber-Optic Liquid-Level Sensors

Liquid-level-measuring systems based on fiber-optics are under development as compact, lightweight alternatives to systems based on float gauges and other conventional sensors. For liquids that pose explosion hazards, fiber-optic sensors are inherently safer because they do not include electrical connections inside tanks. Fiber-optic sensors can be designed in many different forms to exploit reflection and transmission of light to measure liquid levels. Most of them are based on the effects of the indices of refraction of liquids on the waveguide properties of optical fibers: In a typical case, there is a loss of internal reflection of guided electromagnetic modes as a result of contact between the outer surface of optical fiber and a liquid. Hence, a substantial decrease in the light transmitted from one end of the fiber to the other is taken to indicate that liquid has come into contact with a suitably designed probe at the end of the fiber. A system capable of determining the level of liquid to within a known increment of depth could be constructed by placing the probes of a number of such sensors at known increments of depth in a tank.

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Combining Multimode Emissions from Broad Area Laser Diodes into Single-Mode Spots without Feedback

Broad-area laser diodes are the most efficient coherent light sources and are widely used today. The extraordinary efficiency, modulation easiness, availability to virtually any wavelength and compactness are the principle drives stimulating the development of light sources based on laser diodes. However, due to fundamental limitations of laser diode gain medium, the emission from laser diodes has a major drawback — the emission is not spatially coherent. In other words laser diode light is often seen as a light bulb emission that cannot be focused in a diffraction limited spot of λ/2 or easily transmitted as a narrow beam. Despite the fact that kilowatts of multimode power can be easily extracted from a laser diode array, the resulting single-lobe single-element power from a laser diode is always limited by a value of several watts. Many applications are waiting for a spatially coherent laser diode source offering power from 1 to 100W. The potential substitution of YAG and fiber lasers by a compact, direct single- mode laser diode source would bring significant advancements in a number of applications such as LIDAR/LADAR (Light Intensity Detection and Ranging/Light Amplification Detection and Ranging) systems; high-bit-rate, long-haul free space communication systems; industrial processing applications; and many more.

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Design of a Field-Mapped Beam Homogenizer

Light beam homogenizer designs used for decades are largely based upon lenticular lens arrays that date back to the 1940s and 1950s. A more recent design is from the late 1980s that comprises a pair of crossed-cylindrical lenticular lens structures coupled with a condensing lens. The 1980s design has 10 optical surfaces which represents a significant source of optical loss, long beam path (typically ~ 1.5 meters) and high cost from having so many optical elements. Further, this design requires careful and precise alignment of the light beam in relation to the optics comprising the homogenizer, in particular angular rotation of the lenslets and their positioning in the X-Y plane of the optical axis. These designs are unable to produce a homogenized ring illumination, which is useful for ablating polymer insulation from metal bonding pads in microelectronic fabrication of multichip modules and memory chips.

Posted in: ptb catchall, Applications, Photonics, Application Briefs

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Optical Displacement Sensor for Sub-Hertz Applications

NASA’s Jet Propulsion Laboratory, Pasadena, California. A document discusses a sensor made from off-the-shelf electro-optical photo-diodes and electronics that achieves 20 nm/(Hz)1/2 displacement sensitivity at 1 mHz. This innovation was created using a fiber-coupled laser diode (or Nd:YAG) through a collimator and an aperture as the illumination source. Together with a germanium quad photodiode, the above-mentioned displacement sensor sensitivities have been achieved. This system was designed to aid the Laser Interferometer Space Antenna (LISA) with microthruster tests and to be a backup sensor for monitoring the relative position between a proof mass and a spacecraft for drag-free navigation. The optical displacement sensor can be used to monitor any small displacement from a remote location with minimal invasion on the system.

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