Photometry of a Sodium Laser Guide Star at the Starfire Optical Range

Drummond, Jack D.; Telle, John M.; Denman, Craig A.; Hillman, Paul D.; Tuffli, Andrea L.

doi:10.1086/382756

Cited by 16 publications

(15 citation statements)

References 30 publications

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“…In the description of our first set of experiments (Drummond et al 2004), we addressed the relationship between the LGS photon return flux and the astronomical V-magnitude system. Because the V magnitude system for stars is based on a comparison of flux density ( , where dF is the number of dF/dl photons per second per cm 2 and is the wavelength interval) dl with standard stars, and because the filter is much narrower than the stellar flux wavelength distribution, the V magnitude derived for an unknown star is relatively independent of the actual V-filter properties for most normal stars.…”

Section: Spot Radiance Observationsmentioning

confidence: 99%

“…[1] and [2] in Drummond et al 2004), which still has to be corrected for the particular V filter's transmission at 589 nm and corrected to a standard normalized filter area , A 0 V p V ϩ 2.5 log t Ϫ 2.5 log A/A .…”

Section: Spot Radiance Observationsmentioning

confidence: 99%

“…A 0 Drummond et al (2004) derived a useful formula relating photon flux and the astronomical V-magnitude system to a filter's normalized width. For a sodium spectral-line photon flux F in photons s Ϫ1 cm Ϫ2 at the top of the telescope, eq.…”

Section: Spot Radiance Observationsmentioning

confidence: 99%

“…[4] of Drummond et al (2004) can be modified to give a common for a filter with a normalized width of in nm:…”

Section: Spot Radiance Observationsmentioning

confidence: 99%

“…The laser is described by Bienfang et al (2003aBienfang et al ( , 2003b, and the first set of experiments are summarized by Drummond et al (2004). In those tests, a 12 W, 10 cm diameter laser beam (after expansion and steering optics) created an apparent 1.9 m FWHM Gaussian LGS in the mesosphere.…”

Section: Introductionmentioning

confidence: 99%

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Photometry of a Sodium Laser Guide Star from the Starfire Optical Range. II. Compensating the Pump Beam

Drummond¹,

Telle²,

Denman³

et al. 2004

PUBL ASTRON SOC PAC

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ABSTRACT. Measurements of the brightness and size of a mesospheric sodium guide star pumped by a laser launched through an adaptive optics (AO) system are reported from experiments conducted on 2003 July 22 at the Starfire Optical Range. The guide star was produced by a laser launched through a 0.5 m telescope with (closed loop) and without (open loop) higher order atmospheric compensation using an ∼60 actuator AO system and with various laser polarization states. A 3.5 m telescope (without AO) 50 m away from the launch site recorded the closed-and open-loop images. Calibrated using standard stars, the maximum brightness observed for the 8.5 W of compensated pump laser power out of the top of the telescope for a 96% circularly polarized beam was (840 photons s Ϫ1 cm Ϫ2 at the bottom of the atmosphere) for the open-loop beam (where V p 7.35 1 is the V magnitude corrected for the transmission of the V filter at the 589 nm wavelength of the sodium D2 V 1 absorption line) and (800 photons s Ϫ1 cm Ϫ2 ) for the closed-loop beam. It appears that circular polarization V p 7.4 1 enhances the brightness of the return by 75%. Open-loop tests produced an integrated guide star that was 11% brighter than closed-loop, but the guide star produced from a closed-loop circularly polarized pump beam was about 50% of the width of either the open-loop beam or the linearly polarized closed-loop beam. At 0Љ .85 FWHM, or 38 cm at 92 km altitude, the guide star is suitable for many astronomical AO applications. The guide star spot sizes were measured from images reconstructed with multiframe blind deconvolution. Because of optical losses, only 8.5 W of laser power was transmitted out of the top of the telescope. Reducing this by atmospheric extinction, the "power through the mesospheric footprint," or peak Gaussian intensity, was 3.9 mW cm Ϫ2 for the closed-loop circularly polarized laser beam. This is about 60% of the saturation intensity for the optically I sat pumped atom, and 20% of the for the thermally equilibrated atom. I sat

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Section: Spot Radiance Observationsmentioning

confidence: 99%

Section: Spot Radiance Observationsmentioning

confidence: 99%

Section: Spot Radiance Observationsmentioning

confidence: 99%

“…[4] of Drummond et al (2004) can be modified to give a common for a filter with a normalized width of in nm:…”

Section: Spot Radiance Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Photometry of a Sodium Laser Guide Star from the Starfire Optical Range. II. Compensating the Pump Beam

Drummond¹,

Telle²,

Denman³

et al. 2004

PUBL ASTRON SOC PAC

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20 W CW 589 nm sodium beacon excitation source for adaptive optical telescope applications

et al. 2004

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Investigation of return photons from sodium laser beacon excited by a 40-watt facility-class pulsed laser for adaptive optical telescope applications

Bian

Yang

Zuo

et al. 2018

Sci Rep

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The brightness of the artificial beacon is one critical performance parameter for adaptive optics. Here, a 40-watt level narrow-linewidth microsecond pulsed yellow laser is produced at 589 nm with a high repetition frequency of 600 Hz and a pulse duration of 120 μs. An experiment to project the pulse beam up to the sky and measure the fluorescence photon returns of the Na atoms has been held on the 1.8-meter telescope in Lijiang observatory. During the sky test, a laser guide star (LGS) spot is firstly observed with Rayleigh scattering elimination by means of a gateable pulse format. And, the central wavelength of the laser could be accurately locked to be 589.1584 nm with a linewidth of ~0.34 GHz to match that of sodium-D2a line. Optical pumping with circularly polarized light has also been used to increase the brightness of sodium LGS. In order to maximize the return flux, sodium D2b repumping option is done by an electro-optic modulator with the optimum D2a-D2b frequency offset. As a result, a bright sodium LGS with the return flux of 1610 photons/cm2/s is achieved, corresponding to ~47 photons/cm2/s/W of emitted laser power, which represents a significant improvement in terms of brightness reported ever.

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Photometry of a Sodium Laser Guide Star at the Starfire Optical Range

Cited by 16 publications

References 30 publications

Photometry of a Sodium Laser Guide Star from the Starfire Optical Range. II. Compensating the Pump Beam

Photometry of a Sodium Laser Guide Star from the Starfire Optical Range. II. Compensating the Pump Beam

20 W CW 589 nm sodium beacon excitation source for adaptive optical telescope applications

Investigation of return photons from sodium laser beacon excited by a 40-watt facility-class pulsed laser for adaptive optical telescope applications

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