Showing papers by "Jirong Yu published in 2007"
TL;DR: In this article, a coherent Doppler lidar at 2 m wavelength has been built with higher output energy 100 mJ than previously available, based on diode-pumped Ho:Tm:LuLiF, a recently developed laser material that allows more efficient energy extraction.
Abstract: A coherent Doppler lidar at 2 m wavelength has been built with higher output energy 100 mJ than previously available. The laser transmitter is based on diode-pumped Ho:Tm:LuLiF, a recently devel- oped laser material that allows more efficient energy extraction. Single- frequency operation is achieved by a ramp-and-fire injection seeding technique. An advanced photodetector architecture is used incorporating photodiodes in a dual-balanced configuration. A digital signal processing system has been built, allowing real-time display of wind and aerosol backscatter data products. The high pulse energy and receiver efficiency provides for measurement of wind fields to ranges not seen before with 2 m lidars, and example wind measurements were made to show this capability. © 2007 Society of Photo-Optical Instrumentation Engineers.
134 citations
TL;DR: Efficient operation of diode-pumped single-frequency fiber lasers at wavelengths from 1740 to 2017 nm has been demonstrated by using a very short piece of newly developed single-mode active fiber, i.e., heavily thulium-doped germanate glass fiber.
Abstract: Efficient operation of diode-pumped single-frequency fiber lasers at wavelengths from 1740 to 2017 nm has been demonstrated by using a very short piece of newly developed single-mode active fiber, i.e., heavily thulium-doped germanate glass fiber. At 1893 nm, the single-frequency fiber laser has a pump threshold of 30 mW, a slope efficiency of 35%, and maximum output power of 50 mW with respect to the launched power of single-mode pump diodes at 805 nm. To the best of our knowledge, this is the highest lasing efficiency achieved in single-frequency fiber lasers operating near 2 μm. Frequency noise of the single-frequency fiber laser at 1893nm has been characterized and compared with that of single-frequency fiber lasers at 1 and 1.55 μm.
111 citations
06 May 2007
TL;DR: In this paper, a highly efficient Q-switched Ho:YLF laser pumped by a Tm:fiber laser has been designed and demonstrated, when the pump power is 30 W, the pulse energy is 30 mJ at the repetition rate of 100 Hz.
Abstract: A highly efficient Q-switched Ho:YLF laser pumped by a Tm:fiber laser has been designed and demonstrated. When the pump power is 30 W, the pulse energy is 30 mJ at the repetition rate of 100 Hz.
13 citations
01 Jan 2007
TL;DR: In this article, a diode-pumped single-frequency fiber laser with 35% slope efficiency and 50mW output power operating near 2 micrometers was demonstrated, which generated from a 2-cm long piece of highly Tm(3+)-doped germanate glass fiber pumped at 800nm.
Abstract: We demonstrate highly efficient diode-pumped single-frequency fiber laser with 35% slope efficiency and 50mW output power operating near 2 micrometers, which generated from a 2-cm long piece of highly Tm(3+)-doped germanate glass fiber pumped at 800nm.
6 citations
TL;DR: The gap between requirements and demonstration was formidable as discussed by the authors, and the involved scientists and engineers set out to reduce the gap, and through a combination of clever ideas and technology advances over the last 15 years they succeeded.
Abstract: Early concepts to globally measure vertical profiles of vector horizontal wind from space planned on an orbit height of 525 km, a single pulsed coherent Doppler lidar system to cover the full troposphere, and a continuously rotating telescope/scanner that mandated a vertical line of sight wind profile from each laser shot. Under these conditions system studies found that laser pulse energies of approximately 20 J at 10 Hz pulse repetition rate with a rotating telescope diameter of approximately 1.5 m was required. Further requirements to use solid state laser technology and an eyesafe wavelength led to the relatively new 2-micron solid state laser. With demonstrated pulse energies near 20 mJ at 5 Hz, and no demonstration of a rotating telescope maintaining diffraction limited performance in space, the technology gap between requirements and demonstration was formidable. Fortunately the involved scientists and engineers set out to reduce the gap, and through a combination of clever ideas and technology advances over the last 15 years, they have succeeded. This paper will detail the gap reducing factors and will present the current status.
4 citations
28 Jun 2007
TL;DR: 4.0 mm Diameter Enclosure:50.0 Absorbed Watts or 91.7%4.5 mm D diameter Enclosed:59.2 Absor Bed Watts or 82.8%5.0mm Diameter enclosure:66.0%
Abstract: A master oscillator power amplifier, high energy Q-switched 2-micron laser system has been recently demonstrated. The laser and amplifiers are all designed in side-pumped rod configuration, pumped by back-cooled conductive packaged GaAlAs diode laser arrays. This 2-micron laser system provides nearly transform limited beam quality.
30 Jul 2007
TL;DR: In this article, a 2-micron master-oscillator-power-amplifier laser using a fiber-based phase conjugation mirror has been demonstrated and the beam quality improvement and 56% of the PCM reflectivity have been achieved.
Abstract: For the first time, a 2-micron master-oscillator-power-amplifier laser using a fiber based phase conjugation mirror has been demonstrated. The beam quality improvement and 56% of the PCM reflectivity have been achieved.
08 Jul 2007
TL;DR: The current projects at NASA Langley Research Center are the Global Wind Observing Sounder (GWOS) mission preparation, the Laser Risk Reduction Program (LRRP), the Instrument Incubator Program (IIP) compact, rugged Doppler wind lidar project, the Autonomous precision Landing and Hazard detection and Avoidance Technology (ALHAT) project for lunar landing, and the Skywalker project to find and use thermals to extend UAV flight time.
Abstract: NASA Langley Research Center has been developing and using coherent lidar systems for many years. The current projects at LaRC are the Global Wind Observing Sounder (GWOS) mission preparation, the Laser Risk Reduction Program (LRRP), the Instrument Incubator Program (IIP) compact, rugged Doppler wind lidar project, the Autonomous precision Landing and Hazard detection and Avoidance Technology (ALHAT) project for lunar landing, and the Skywalker project to find and use thermals to extend UAV flight time. These five projects encompass coherent lidar technology development; characterization, validation, and calibration facilities; compact, rugged packaging; computer simulation; trade studies; data acquisition, processing, and display development; system demonstration; and space mission design. This paper will further discuss these activities at LaRC.
06 May 2007
TL;DR: In this article, a diode pumped, injection seeded MOPA with a transform limited line width and diffraction limited beam quality is presented, which produces over 300mJ energy at 10 Hz repetition rate.
Abstract: The design of a diode pumped, injection seeded MOPA with a transform limited line width and diffraction limited beam quality is presented. This lidar transmitter produces over 300mJ energy at 10 Hz repetition rate.
28 Jan 2007
TL;DR: In this paper, the beam quality improvement of 2 μm laser using fiber-based phase conjugation mirror has been demonstrated, where single frequency operation is necessary to lower threshold.
Abstract: For the first time, beam quality improvement of 2 μm laser using fiber based phase conjugation mirror has been demonstrated. Single frequency operation is necessary to lower threshold. The reflectivity of the PCM is ~50%.
19 Jun 2007
TL;DR: The IIP project reported here is an effort to increase the ruggedness and to compactly package the NASA Langley Research Center (LaRC) state-of-the-art laser technology as mentioned in this paper.
Abstract: High-accuracy, vertical profiles of the horizontal vector wind in earth s atmosphere, with the global coverage of an orbiting sensor, are a highly desired measurement of NASA, NOAA, and many other agencies and countries. It is the consensus of NASA and NOAA that the most cost effective, lowest risk measurement method with the earliest achievable mission date is the hybrid Doppler lidar method which utilizes both coherent- and direct-detection Doppler lidars to obtain the desired profiles. NASA Langley Research Center (LaRC) has advanced the 2-micron pulsed solid-state laser greatly over the past 15 years and has recently demonstrated 1.2 J of pulse energy whereas the requirement for a 400-km hybrid Doppler lidar mission is only 0.25 J. The IIP project reported here is an effort to increase the ruggedness and to compactly package the LaRC state-of-the-art laser technology.
06 May 2007
TL;DR: In this article, a diode pumped, injection seeded MOPA with a transform limited line width and diffraction limited beam quality is presented, which produces over 300mJ energy at 10 Hz repetition rate.
Abstract: The design of a diode pumped, injection seeded MOPA with a transform limited line width and diffraction limited beam quality is presented. This lidar transmitter produces over 300mJ energy at 10 Hz repetition rate.
Proceedings Article•
06 May 2007TL;DR: In this paper, the design and fabrication of a compact coherent laser radar transmitter for Troposphere wind sensing is under way, which is composed of a seed laser, a ring oscillator, and a double pass amplifier.
Abstract: 2 micron solid-state lasers are the primary choice for coherent Doppler wind detection. As wind lidars, they are used for wake vortex and clear air turbulence detection providing air transport safety. In addition, 2 micron lasers are one of the candidates for CO2 detection lidars. The rich CO2 absorption line around 2 micron, combined with the long upper state life of time, has made Ho based 2 micron lasers a viable candidate for CO2 sensing DIAL instrument. The design and fabrication of a compact coherent laser radar transmitter for Troposphere wind sensing is under way. This system is hardened for ground as well as airborne applications. As a transmitter for a coherent wind lidar, this laser has stringent spectral line width and beam quality requirements. Although the absolute wavelength does not have to be fixed for wind detection, to maximize return signal, the output wavelength should avoid atmospheric CO2 and H2O absorption lines. The base line laser material is Ho:Tm:LuLF which is an isomorph of Ho:Tm:YLF. LuLF produces 20% more output power than Ho:Tm:YLF. In these materials the Tm absorption cross-section, the Ho emission cross-section, the Tm to Ho energy transfer parameters and the Ho (sup 5) I (sub 7) radiative life time are all identical. However, the improved performance of the LuLF is attributed to the lower thermal population in the (sup 5) I (sub 8) manifold. It also provides higher normal mode to Q-switch conversion than YLF at high pump energy indicating a lower up-conversion. The laser architecture is composed of a seed laser, a ring oscillator, and a double pass amplifier. The seed laser is a single longitudinal mode with a line width of 13 KHz. The 100mJ class oscillator is stretched to 3 meters to accommodate the line-width requirement without compromising the range resolution of the instrument. The amplifier is double passed to produce greater than 300mJ energy.
28 Jan 2007
TL;DR: In this article, a diode-pumped single-frequency fiber laser with 35% slope efficiency and 50mW output power operating near 2μm was demonstrated, which generated from a 2-cm long piece of highly Tm3+-doped germanate glass fiber pumped at 800nm.
Abstract: We demonstrate highly efficient diode-pumped single-frequency fiber laser with 35% slope efficiency and 50mW output power operating near 2μm, which generated from a 2-cm long piece of highly Tm3+-doped germanate glass fiber pumped at 800nm