Photonics

Demystifying Spectroscopy

Spectroscopy techniques date back to Isaac Newton’s first studies of light and today provide researchers with a better understanding of what happens at the atomic and molecular level when matter interacts with light. Advances in electro-optics, high-speed array detectors, inexpensive optical fibers and powerful computers have spurred the growth of miniature spectroscopy. This miniaturization has increasingly made optical spectroscopy the sensing technique of choice for many real-world applications.

Posted in: Features, Photonics, Articles

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V-Assembly Dual-Head Efficiency Resonator (VADER) Laser Transmitter

The combined features form a unit with new performance levels. A complete demonstration breadboard unit for advanced development as a high-TRL (technology readiness level) system has been constructed and characterized. Infusion of several new component technologies, such as ceramic:YAG material and high-power laser diode arrays (LDAs), combined with a proprietary minimal part count architecture, has resulted in dramatic performance gains. The proprietary dual-head configuration employs a pair of side-pumped laser slabs, optically in series in the cavity, but at opposing polarization orientations. This promises tremendous power range scalability, simplified and symmetrical thermal lens control, unprecedented stored energy extraction efficiency, and inherent diffraction limited TEM00 beam quality.

Posted in: Tech Briefs, Physical Sciences, Photonics, Briefs

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Twin Head Efficient Oscillator Development for the ACE Multi- Beam Lidar and 3D-Winds

This technology is applicable to atmospheric lidar, Doppler wind measurements, interplanetary laser communications, and materials processing. The Twin Head Efficient Oscillator (THEO) concept uses a pair of smaller, identical laser pump modules, oriented to remove asymmetrical thermo-optical effects typical in single-slab lasers such as HOMER (High Output Maximum Efficiency Resonator), MLA (Mercury Laser Altimeter), LOLA Lunar Orbiter Laser Altimeter, and GLAS (Geoscience Laser Altimeter), while simultaneously increasing efficiency and lifetime. This creates 100+ mJ pulses in an oscillator-only design, with reduced risk of optical damage, record efficiency, high stability, long life, and high TEM00 beam quality typical of much smaller rod-based cavities. Near-field-beam quality is critical to efficient second harmonic generation (SHG 532 nm), which is typically poor in slab-based Nd:YAG lasers.

Posted in: Physical Sciences, Photonics, Briefs

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Planetary Polarization Nephelometer

Instrument provides more detailed information on aerosols encountered in a planetary environment. Aerosols in planetary atmospheres have a significant impact on the energy balance of the planets, yet are often poorly characterized. An in situ instrument was developed that would provide more diagnostic information on the nature of aerosols it encountered if deployed on a planetary descent probe. Previous probe instruments only measured intensity phase functions, but much particle ambiguity remains with only this information. Adding the polarization phase function greatly reduces particle characteristic ambiguities, but also adds more challenges in designing a measurement approach. Laboratory instrumentation to measure intensity and polarization phase functions have existed since the early 1970s, but these instruments employed quarter-wave plates and Pockels cells to modulate the illuminating beam and the scattered light to isolate the intensity and polarization phase functions. Both of these components are unstable except under tightly controlled thermal conditions. This solution avoids the use of thermally sensitive components such as quarter- wave plates or Pockels cells, and avoids requiring the detectors to be placed around the sensing volume.

Posted in: Physical Sciences, Photonics, Briefs

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GaSb-Based Diode Lasers for Remote Detection of Carbon Dioxide

Lidar systems measure carbon dioxide to understand better the impact of the carbon cycle on global warming and climate change. Monolithic ridge-waveguide GaSbbased diode lasers were fabricated with a second-order, laterally etched Bragg grating to generate single-mode emission from InGaAsSb/AlGaAsSb multiquantum- well structures. In this design, the monolithic Type-I GaSb-based diode lasers use grating structures that exhibit low internal loss. The frequency-stable diode lasers meet the needs of high power (>50 mW) and narrow linewidth (≈100 kHz). These devices are strong candidates for replacement of the solidstate light sources. Furthermore, this design is not limited to this wavelength. By optimizing the quantum well, and the optical design, this innovation can adapt to any wavelength within the 2-to-3-μm spectral window with similar performance.

Posted in: Photonics, Briefs

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Optical Tunable-Based Transmitter for Multiple High-Frequency Bands

Applications include satellite communications, optical communications networks, and RF antenna applications. The purpose of this innovation is to be able to deliver, individually or simultaneously, multiple microwave high-frequency bands including, but not limited to, L (1.5 GHz), C (7 GHz), X (8.4 GHz), Ku (14.5 GHz), Ka (32 GHz), and Q (38 GHz) frequencies at high data rates and with minimal hardware, particularly for use in satellite-to-satellite communications applications. Additionally, this innovation would be a satellite-based transmitter with a significant reduction in weight, mass, and power when compared to current, conventional technologies.

Posted in: Physical Sciences, Photonics, Briefs

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A High-Repetition-Rate Seeded Optical Fiber Amplifier (SOFiA) for the LIST Mission and Next-Generation Satellite Laser Ranging

A document describes a fiber/solid-state hybrid seeded regenerative amplifier capable of achieving high output energy with tunable pulse widths for satellite laser ranging (SLR) applications. The diode-pumped solid-state (DPSS) regenerative amplifier cavity utilizes a pair of Nd:YAG zigzag slabs oriented orthogonally to one another in order to circularize thermal lensing effects and simplify optical correction schemes. The short-pulsed seed laser is a fiber-coupled 1,064-nm narrow-band (<0.02 nm) diode laser that is intensity modulated by a fiber Mach-Zehnder electro-optic modulator, enabling continuously tunable seed pulse widths in the 0.2-to-2.0-ns range.

Posted in: Photonics, Briefs

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