Studies of a mesospheric sodium guidestar pumped by continuous-wave sum-frequency mixing of two Nd:YAG laser lines in lithium triborate

Telle, John M.; Drummond, Jack D.; Denman, Craig A.; Hillman, Paul D.; Moore, Gerald; Novotny, Steven J.; Fugate, Robert Q.

doi:10.1117/12.673121

Cited by 9 publications

(5 citation statements)

References 11 publications

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“…The ratio of these two peaks should be 5:3 for sodium atoms in thermal equilibrium, whereas we see as much as 12:1 for circular polarization and 3.1:1 for linear polarization, indicating evidence of strong optical pumping for circularly-polarized light and perhaps saturation for linear polarization pumping of the D 2b transition. Not shown are the radiance results for linear polarization [6] as they are about two times lower than the results for circular polarization. A reason for this response for linear polarization to saturate more than the response for circular polarization may be due to atoms becoming trapped in F' = 1 (the energy level associated with the D 2b absorption).…”

Section: Guidestar Characterstics and Radiancementioning

confidence: 67%

“…Based on the measured sodium column densities from our experiments, the measured slopes of guidestar radiance versus fasor power are about three times less than the maximum possible theoretical values [6]. We believe the two most probable reasons for this discrepancy may be 1) atoms are becoming trapped in F' = 1, and 2) atoms are recoiling off the pump fasor line into a weakly-pumped velocity class.…”

Section: Guidestar Characterstics and Radiancementioning

confidence: 72%

“…Sky tests of the 50-W fasor [6] have been conducted during occasional weekly periods within the schedule for the 3.5-m telescope. The main goals of these tests were to demonstrate the reliability of the system, check bore sight of the launch optics at various elevations, image the beacon to obtain its size (Figs.…”

Section: Guidestar Characterstics and Radiancementioning

confidence: 99%

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Characteristics of sodium guidestars created by the 50-watt FASOR and first closed-loop AO results at the Starfire Optical Range

et al. 2006

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A computer-automated cw sodium guidestar FASOR (Frequency Addition Source of Optical Radiation) producing a single frequency 589-nm beam with up to 50 W for mesospheric beacon generation has been integrated with the 3.5-m telescope at the Starfire Optical Range, Kirtland AFB, New Mexico. Radiance tests have produced a peak guidestar V 1 magnitude = 5.1 (~7000 photons/s/cm 2 at zenith) for 30 W of circularly polarized pump power in November 2005. Estimated theoretical maximum guidestar radiance is about 3 times greater than measured values indicating saturation due to atoms possibly becoming trapped in F' = 1 and/or atomic recoil. From sky tests over 3.5 years, we have tracked the annual variation of the sodium column density by measuring the return flux as a function of fasor power and determining the slope at zero power. The maximum occurs on October 30 and the minimum on May 30, with corresponding predicted returns of 8000 (V 1 = 4.8) and 3000 (V 1 = 5.8) ph/s/cm 2 with 50 W of fasor power and circular polarization. The effect of the Earth's magnetic field on the radiance of the sodium laser guidestar (LGS) from various azimuths and elevations has been measured. The peak return flux over our observatory occurs at [az=198°; el=+71°], compared with the direction of the magnetic field lines at [190°; +62°], and it can vary by a factor of 3 over the sky above el = 30°. First results for non-optimized sodium LGS adaptive optics (AO) closed-loop operation have been obtained using binary stars. Strehl ratios of 0.03 have been measured at 850 nm and a 0.14 arc second binary star has been resolved during first closed loop observations. Guidestar characteristics, including radiance, size, and Rayleigh backscatter, the sodium LGS wavefront sensor (WFS) AO system, and recent closed-loop results on binary stars are presented.

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Section: Guidestar Characterstics and Radiancementioning

confidence: 67%

Section: Guidestar Characterstics and Radiancementioning

confidence: 72%

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Characteristics of sodium guidestars created by the 50-watt FASOR and first closed-loop AO results at the Starfire Optical Range

et al. 2006

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“…As mentioned earlier, 589nm laser photons are extremely expensive, on the order of 50,000 to 250,000 USD per Watt of laser system output power. Thus it is certainly cost effective to invest in quality BTO optics in order to maximize throughput and enable good polarization control so as to save precious laser photons (circular polarized beams have the capability to increase sodium photon return by factors up to three 13 depending on the laser spectro-temporal format and observatory site).…”

Section: Lessons Learnedmentioning

confidence: 99%

Gemini South multi-conjugate adaptive optics (GeMS) laser guide star facility on-sky performance results

et al. 2012

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With two to three deformable mirrors, three Natural Guide Stars (NGS) and five sodium Laser Guide Stars (LGS), the Gemini Multi-Conjugate Adaptive Optics System (Gemini MCAO a.k.a. GeMS) will be the first facility-class MCAO capability to be offered for regular science observations starting in 2013A. The engineering and science commissioning phase of the project was kicked off in January 2011 when the Gemini South Laser Guide Star Facility (GS LGSF) propagated its 50W laser above the summit of Cerro Pachón, Chile. GeMS commissioning has proceeded throughout 2011 and the first half of 2012 at a pace of one 6-to 10-night run per month with a 5-month pause during the 2011 Chilean winter. This paper focuses on the LGSF-side of the project and provides an overview of the LGSF system and subsystems, their top-level specifications, design, integration with the telescope, and performance throughout commissioning and beyond. Subsystems of the GS LGSF include: (i) a diode-pumped solid-state 1.06+1.32 micron sum-frequency laser capable of producing over 50W of output power at the sodium wavelength (589nm); (ii) Beam Transfer Optics (BTO) that transport the 50W beam up the telescope, split the beam five-ways and configure the five 10W beams for projection by the Laser Launch Telescope (LLT) located behind the Gemini South 8m telescope secondary mirror; and (iii) a variety of safety systems to ensure safe laser operations for observatory personnel and equipment, neighbor observatories, as well as passing aircrafts and satellites.

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“…Current narrow linewidth sodium guidestar lasers are either constructed using slab [1][2][3] or fiber laser technology [4][5][6][7][8][9][10][11][12][13][14] . Slab technology generally involves sum-frequency mixing of 1064 and 1319 nm in a lithium triborate crystal to obtain 589 nm.…”

Section: Introductionmentioning

confidence: 99%

Investigation of the impact of fiber Bragg grating bandwidth on the efficiency of a Raman resonator

2015

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Significant spectral power leakage was found to occur around the high reflectivity fiber Bragg gratings (FBGs) defining a 1121 nm Raman resonator cavity comprised of PM 10/125 germanosilicate fiber. This cavity was part of a Raman system pumped with broad linewidth 1069 nm and seeded with narrow linewidth 1178 nm. The 1069 nm upon entering the resonator cavity was Raman converted to 1121 nm which then amplified the 1178 nm as it passed through the cavity. Spectral leakage of 1121 nm light from the resonator cavity resulted in sub-optimal amplification of 1178 nm which forced usage of longer resonator cavities having a decreased threshold for Stimulated Brillouin Scattering. Upon study of 1121 nm linewidth broadening as a function of resonator length for cavities employing 3 nm FBGs, differences in the percentage of 1121 nm power spectrally leaking past the output FBG as a function of the 1121 nm intracavity power propagating in the forward direction are not experimentally discernible for resonator cavities longer than 40 m. But, for cavity's shorter than 40 m, the percentage of 1121 nm power spectrally leaking past the output FBG decreased significantly for similar 1121 nm intracavity power levels. For all cavity lengths, a nearly linear relationship exists between percent 1121 nm power leakage and intracavity power levels. Also, cavities employing broader bandwidth FBGs experience less 1121 nm power leakage for similar 1121 nm intracavity power levels. Finally, modeling predictions of Raman system performance are greatly improved upon usage of experimentally derived effective FBG reflectivities.

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Studies of a mesospheric sodium guidestar pumped by continuous-wave sum-frequency mixing of two Nd:YAG laser lines in lithium triborate

Cited by 9 publications

References 11 publications

Characteristics of sodium guidestars created by the 50-watt FASOR and first closed-loop AO results at the Starfire Optical Range

Characteristics of sodium guidestars created by the 50-watt FASOR and first closed-loop AO results at the Starfire Optical Range

Gemini South multi-conjugate adaptive optics (GeMS) laser guide star facility on-sky performance results

Investigation of the impact of fiber Bragg grating bandwidth on the efficiency of a Raman resonator

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