GPD Optoelectronics (United States)

Realizing a high solar light conversion magnitude in Cr,Nd: YAG transparent ceramic is crucial to its applications in solar pumped solid state lasers. In this study, high quality Cr,Nd:YAG transparent laser ceramics with homogeneous microstructure and theoretical transmittance were fabricated, and an efficient laser oscillation of watt-level was realized by pumping ceramic at 808 nm. There were no any characteristic absorptions corresponding to Cr2+ or Cr4+ ions detected, even when the Cr3+ ion doping concentration reached 0.6 at.%. Increasing Cr3+ and Nd3+ doping concentrations significantly enhanced the emission intensity of ceramics at 1.06 µm, and energy transfer efficiency of the 0.3 at.% Cr,Nd: YAG ceramics was increased from 14.9% to 36.9% when increasing Nd3+ ion concentration from 0.3 at.% to 1.0 at.%, with an increasing magnitude of 247.6%. The results indicated that Cr,Nd: YAG transparent ceramic is a promising gain medium for solar pumped solid state lasers.

Cooled detectors for IR, visible, UV and X-rays often require a preamplifier that can operate at deep cryogenic temperature, down to the liquid-helium range. Preamplifiers based on available silicon or gallium arsenide transistors have not been entirely satisfactory. With this in mind, we have been developing junction field-effect transistors (JFETs) based on germanium. Our objective has been to achieve stable dc characteristics and very low noise down to as low a cryogenic as possible. We have obtained good dc characteristics down to liquid-helium temperature and low noise down to ≈30 K with Ge JEFTs. Between approximately 30 and 80 K, low-frequency gate-referred noise voltage is ≈30-60 nV/rtHz at 1 Hz, decreasing to <2 nV/rtHz above ≈1 kHz for 40 μm by 1560 μm gate n-channel Ge JFETs with drain current of 330 μA and dissipating approximately 400 μW. For lower and higher drain current the 1/f noise remains approximately the same, but the white noise increases or decreases as expected. We are continuing development with the goal of extending the same low noise characteristics down to 4K.

We have begun investigation and development of cryogenic semiconductor power devices (diodes, bipolar transistors and field-effect transistors) based on germanium. The motivation is NASA's interest in electronics that can operate down to deep cryogenic temperatures (as low as 30-40 K) for exploration of the outer planets and other Solar System bodies that present cold environments as well as for future space observatories. There are also potential applications related to cryogenic/superconducting motors and generators and power distribution and storage. We have characterized available Ge diodes and bipolar transistors at cryogenic temperatures and have begun examining MIS (metal-insulator-semiconductor) capacitors on Ge. Our investigations show that all these types of devices can operate from room temperature down to 20 K or lower.

Recently several THz sampling detection systems have been used to characterize the temporal and spatial distribution of free- space broadband, pulsed electromagnetic radiation (THz beams). Free-space sampling systems use electro-optic or magneto-optic sensors and a femtosecond laser system, to provide diffraction-limited spatial resolution, picosecond temporal resolution, and DC-THz spectral bandwidth. In this paper, we review recent progress and preliminary applications of free- space electro-optic and magneto-optic sensors.

Packaging technology is described for the DM-1062 gigabit optical module. This module is the IBM offering to comply with ANSI XT39.3 Fiber Channel Standard (FCS) for 1.0625 Gb/s optoelectronic transceiver with integrated serializer/deserializer functions. Performance data for this module is discussed as well as extensions of this technology to lower cost optical devices.

This paper describes a newly developed compact high reliability fiber coupled laser diode which is capable of providing enhanced performance under extreme environmental conditions including a very wide operating temperature range. Careful choice of package materials to minimize thermal and mechanical stress, used with proven manufacturing methods, has resulted in highly stable coupling of the optical fiber pigtail to a high performance MOCVD- grown Multi-Quantum Well laser chip. Electro-optical characteristics over temperature are described together with a demonstration of device stability over a range of environmental conditions. Real time device lifetime data is also presented.