Micro non-planar ring oscillator (micro-NPRO

NASA’s laser mount technology introduces a unique flexible crystal mount to accommodate the dynamics of thermal expansion to eliminate unsymmetrical thermally induced mechanical stresses on the crystal. In addition, while the mount accommodates thermal expansion, it also offers fixed placement of the crystal to maintain alignment and provides continuous and uniform surface contact between the mount and crystal for rapid dissipation of heat. The mount is compatible with any heat sink reservoir. The mount design allows unrestrained thermal expansion of the crystal in two dimensions (i.e. a- and c- axes) because of the design shown in the figure below. The L-shape blocks also deliver cooling to the crystal by providing a path to the heat sink reservoir. The L-shape blocks are manufactured with a high thermal conductivity material such as copper. A softer material with high thermal conductivity such as indium is used to buffer the interface between the crystal and the L-shape blocks surfaces. A coolant medium acts to transfer the heat from the crystal to the cooled mount. Cooling can be provided in different ways – for example by water or by heat pipes with radiator (for use in space). The springs used to hold the laser crystal also provide the adjustment method to align the beam, and once aligned, the crystal mount is very stable. The related patent is now available to license. Please note that NASA does not manufacture products itself for commercial sale.

NASA Glenn's researchers have developed a means of transporting multiple radio frequency carriers through a common optical beam. In contrast to RF infrastructure systems alone, this type of hybrid RF/optical system can provide a very high data-capacity signal communication and significantly reduce power, volume, and complexity. Based on an optical wavelength division multiplexing (WDM) technique, in which optical wavelengths are generated by a tunable diode laser (TDL), the system enables multiple microwave bands to be combined and transmitted all in one unit. The WDM technique uses a different optical wavelength to carry each separate and independent high-frequency microwave band (e.g., L, C, X, Ku, Ka, Q, or higher bands). Since each RF carrier operates at a different optical wavelength, the tunable diode laser can, with the use of an electronic tunable laser controller unit, adjust the spacing wavelength and thereby minimize any crosstalk effect. Glenn's novel design features a tunable laser, configured to generate multiple optical wavelengths, along with an optical transmitter. The optical transmitter modulates each of the optical wavelengths with a corresponding RF band and then encodes each of the modulated optical wavelengths onto a single laser beam. In this way, the system can transmit multiple radio frequency bands using a single laser beam. Glenn's groundbreaking concept can greatly improve the system flexibility and scalability - not to mention the cost of - both ground and space communications.

State of the art space-based LIDARs typically require a telescope with sufficient area to increase the return signal on the detector to levels above the noise floor of the detectors. Two major drivers of the signal-to-noise ratio (SNR) on the detectors are the laser output energy and the round trip distance traveled by the laser signal. The SNR on the detectors can be increased by increasing the telescope reflector area or by decreasing the system noise. If these techniques are not an option, this method can be used to separate stray light from polarized laser light in the LIDAR system and improve the SNR. The method includes generating a beam of azimuthally polarized or OAM light utilizing an optical transmitter comprising a laser light source. The method includes providing an optical receiver including optical sensors at a focal plane with a photon sieve that produces a ring pattern on the focal plane corresponding to a laser return signal. The ring pattern comprises azimuthally polarized or OAM light that is transmitted by the transmitter and reflected towards the receiver. The photon sieve is utilized to cause stray light that is not polarized to cluster centrally, and away from the ring pattern created by the LIDAR signal. This technology could also be used with space based and terrestrial LIDAR for encrypted line of sight communications. The unique revolution frequencies of the LIDAR make any attempt to intercept the communication pointless for those who don&#39t know the specific mode of the source. The lidar system also has use cases for short range navigation for Urban Air Mobility (UAM) vehicles providing input as to whether there is significant enough clear air turbulence on a given path as to be dangerous to an aerial vehicle.

The new fabrication method is an electron lithography scheme enabling monolithic integration of multiple photonic devices on a single PIC. The technology was demonstrated by integrating both a widely-tunable distributed Bragg reflector (DBR) and distributed feedback (DFB) lasers on the same substrate. By controlling the central gap width and etch depth along the laser mirror length (shown in the figure below) the reflectivities can be tuned and the desired laser characteristics can be achieved without additional lithography cycles. Initially demonstrated on an indium phosphide substrate with DBR and DFB elements, the platform technology shows promise for various other materials and devices like III-V and II-VI semiconductors, silicon-on-insulator (SOI), and planar lightwave circuits (PLCs). With this versatility, the invention described here can streamline PIC production across diverse applications. Proof-of-concept results showcase the lithographic technique’s ability to produce high-performance photonic devices with side-mode suppression ratios over 50 dB (figure on the right) and output powers exceeding 5 mW. These metrics, combined with the lithographic simplicity, highlight the technology’s potential to reduce costs and accelerate PIC manufacturing. Please note that NASA does not manufacture products itself for commercial scale.

For this new laser concept, a relatively short but large core fiber doped by active lasing material is used in place of a conventional solid state crystal as the amplifier gain media in a free-space configuration. The technology avoids the usual problems of low thresholds for catastrophic optical damage and other nonlinear loss processes in fiber lasers by increasing the fiber core diameter of a standard 9 microns single mode fiber to the order of 1 mm, thereby permitting peak powers to be increased by factors of 10,000. The usual degradation of single mode propagation in large diameter fibers is avoided by keeping fiber lengths short, thereby staying within a free-space single mode propagation regime.