Low-Noise, Large-Area Quad Photoreceivers Based on Low-Capacitance Quad Photodiodes

The Laser Interferometry Space Antenna’s (LISAs) scientific mission to detect gravity waves demands stringent noise limits on the system components, especially the large-area quad photoreceiver front end, for ultra-high-precision (≈10 pm/Hz1/2) distance measurements. The optical LO (local oscillator) power on LISA is limited to 100 μW to keep power dissipation and thermal fluctuation low on the optical bench. Consequently, a large-area quad photoreceiver having an equivalent input current noise of the order of 1 pm/Hz1/2 is needed. Additionally, the quad photoreceiver must demonstrate low crosstalk between individual quadrants to allow accurate direction sensing of the incoming optical beam. This performance must be achieved over a bandwidth of 2 to 20 MHz to meet LISA’s requirements. Commercially available quad photodetectors do not have the combination of large area, low capacitance (and therefore low noise), and low crosstalk, which is critical for LISA’s scientific objectives.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Physical Sciences, Antennas, Lasers, Noise


Wavefront Sensing Analysis of Grazing Incidence Optical Systems

As a metrology tool, this method allows integration of high-angular-resolution optics without the use of normal incidence interferometry. Wavefront sensing is a process by which optical system errors are deduced from the aberrations in the image of an ideal source. The method has been used successfully in near-normal incidence, but not for grazing incidence systems. This innovation highlights the ability to examine outof- focus images from grazing incidence telescopes (typically operating in the x-ray wavelengths, but integrated using optical wavelengths) and determine the lower-order deformations. This is important because as a metrology tool, this method would allow the integration of high angular resolution optics without the use of normal incidence interferometry, which requires direct access to the front surface of each mirror.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Information Sciences, Photonics, Failure analysis, Imaging and visualization, Optics


RxGen General Optical Model Prescription Generator

RxGen is a prescription generator for JPL’s in-house optical modeling software package called MACOS (Modeling and Analysis for Controlled Optical Systems), which is an expert optical analysis software package focusing on modeling optics on dynamic structures, deformable optics, and controlled optics.

Posted in: Briefs, ptb catchall, Tech Briefs, Photonics, Computer software and hardware, Optics, Medical equipment and supplies, Pharmaceuticals


Mode-Field Diameter and “Spot Size” Measurements of Lensed and Tapered Specialty Fibers

Lensed and tapered specialty fibers are designed to optimize coupling between the fiber and various optical components such as edge-emitting laser diodes and AWGs. The light from these fibers forms a focus at some finite distance away from the fiber end. The Mode-Field Diameter (MFD) and corresponding spot size of these fibers is typically in the range of 5 microns or less. These small spot sizes and corresponding high divergence present challenges to near-field and far-field measurements. Typically the near-field measurements are limited by the optical performance, and the far-field measures must extend to very large angles. Results of measurements of 6 commercially available fibers are presented here, including different type lensed/tapered fibers (4 axially symmetric and 1 elliptical) and a standard single-mode fiber for reference. Also, since the focused beams are in free space, there are some fundamental questions as to the applicability of the MFD, a measure originally formulated to describe the field distribution within a fiber.

Posted in: Articles, Features, ptb catchall, Photonics, Measurements, Fiber optics


Designing COTS LCD Displays For Rugged Applications

Innovation, demand, and falling prices have resulted in high quality large format commercial-off-the-shelf (COTS) LCD displays moving from the living room to high availability, mission critical applications.

Posted in: Articles, Applications, ptb catchall, Photonics, Human machine interface (HMI), Displays


Organic Solar Cell

Heliatek GmbH (Dresden, Germany) has developed 1.1 cm² tandem cells manufactured with a low temperature deposition process that have an efficiency of 9.8 %, a new world record for organic solar cells. The percentage was measured and certified by the independent Fraunhofer ISE CalLab (Freiburg, Germany) under standard test conditions.

Posted in: Products, Products, ptb catchall, Photonics


Metal Adapter

The ELIO® AQ metal adapter from Souriau (York, PA) enables a standard ELIO® optical contact to be inserted into the size-8 Quadrax cavity of several connector types. The ELIO® AQ adapter is already available for connectors in the MIL-DTL-38999/EN3645 series III, ARINC 404, and ARINC 600 ranges. The adapter operates in a harsh operating environment, with temperatures from -65°C to +125°C and intense vibration.

Posted in: Products, Products, ptb catchall, Photonics


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