Rotation sensors (gyros) and accelerometers are essential components for all precision-guided weapons and autonomous mobile surveillance platforms. MEMS gyro development has been based primarily on the properties of moving mass to sense rotation and has failed to keep pace with the concurrent development of MEMS accelerometers because the reduction of size and therefore mass is substantially more detrimental to the performance of gyros than to accelerometers. A small ({approx}0.2 cu in), robust ({approx}20,000g), inexpensive ({approx}$500), tactical grade performance ({approx}10-20 deg/hr.) gyro is vital for the successful implementation of the next generation of ''smart'' weapons and surveillance apparatus. The range of applications (relevant to Sandia's mission) that are substantially enhanced in capability or enabled by the availability of a gyro possessing the above attributes includes nuclear weapon guidance, fuzing, and safing; synthetic aperture radar (SAR) motion compensation; autonomous air and ground vehicles; gun-launched munitions; satellite control; and personnel tracking. For example, a gyro of this capability would open for consideration more fuzing options for earth-penetration weapons. The MEMS gyros currently available are lacking in one or more of the aforementioned attributes. An integrated optical gyro, however, possesses the potential of achieving all desired attributes. Optical gyros use the properties of light to sense rotation and require no moving mass. Only the individual optical elements required for the generation, detection, and control of light are susceptible to shock. Integrating these elements immensely enhances the gyro's robustness while achieving size and cost reduction. This project's goal, a joint effort between organizations 2300 and 1700, was to demonstrate an RMOG produced from a monolithic photonic integrated circuit coupled with a SiON waveguide resonator. During this LDRD program, we have developed the photonic elements necessary for a resonant micro-optical gyro. We individually designed an AlGaAs distributed Bragg reflector laser; GaAs phase modulator and GaAs photodiode detector. Furthermore, we have fabricated a breadboard gyroscope, which was used to confirm modeling and evaluate signal processing and control circuits.
We have used selective AlGaAs oxidation, dry-etching, and high-gain semiconductor laser simulation to create new in-plane lasers with interconnecting passive waveguides for use in high-density photonic circuits and future integration of photonics with electronics. Selective oxidation and doping of semiconductor heterostructures have made vertical cavity surface emitting lasers (VCSELs) into the world's most efficient low-power lasers. We apply oxidation technology to improve edge-emitting lasers and photonic-crystal waveguides, making them suitable for monolithic integrated microsystems. Two types of lasers are investigated: (1) a ridge laser with resonant coupling to an output waveguide; (2) a selectively-oxidized laser with a low active volume and potentially sub-milliAmp threshold current. Emphasis is on development of high-performance lasers suited for monolithic integration with photonic circuit elements.
A two-dimensional (2D) photonic crystal is an attractive alternative and complimentary to its 3D counterpart, due to fabrication simplicity. A 2D crystal, however, confines light only in the 2D plane, but not in the third direction, the z-direction. Earlier experiments show that such a 2D system can exist, providing that the boundary effect in z-direction is negligible and that light is collimated in the 2D plane. Nonetheless, the usefulness of such 2D crystals is limited because they are incapable of guiding light in z-direction, which leads to diffraction loss. This drawback presents a major obstacle for realizing low-loss 2D crystal waveguides, bends and thresholdless lasers. A recent theoretical calculation, though, suggests a novel way to eliminate such a loss with a 2D photonic crystal slab. The concept of a lightcone is introduced as a criterion for fully guiding and controlling light. Although the leaky modes of a crystal slab have been studied, there have until now no experimental reports on probing its guided modes and band gaps. In this paper, a waveguide-coupled 2D photonic crystal slab is successfully fabricated from a GaAs/Al{sub x}O{sub y} material system and its intrinsic transmission properties are studied. The crystal slab is shown to have a strong 2D band gap at {lambda} {approximately} 1.5 {micro}m. Light attenuates as much as {approximately}5dB per period in the gap, the strongest ever reported for any 2D photonic crystal in optical {lambda}. More importantly, for the first time, the crystal slab is shown to be capable of controlling light fully in all three-dimensions. The lightcone criterion is also experimentally confirmed.
In-situ optical diagnostics and ion beam diagnostics for plasma-etch and reactive-ion-beam etch (RIBE) tools have been developed and implemented on etch tools in the Compound Semiconductor Research Laboratory (CSRL). The optical diagnostics provide real-time end-point detection during plasma etching of complex thin-film layered structures that require precision etching to stop on a particular layer in the structure. The Monoetch real-time display and analysis program developed with this LDRD displays raw and filtered reflectance signals that enable an etch system operator to stop an etch at the desired depth within the desired layer. The ion beam diagnostics developed with this LDRD will permit routine analysis of critical ion-beam profile characteristics that determine etch uniformity and reproducibility on the RIBE tool.