Measuring the return flux for a sodium beacon created by combining two laser beams

Keith Wyman; Lee Kann; Alexander Hamm; Mark Eickhoff; Jack Drummond; Olivia Byrd; Robert Johnson

doi:10.1117/12.2310201

10 July 2018 Measuring the return flux for a sodium beacon created by combining two laser beams

Keith Wyman, Lee Kann, Alexander Hamm, Mark Eickhoff, Jack Drummond, Olivia Byrd, Robert Johnson

Proceedings Volume 10703, Adaptive Optics Systems VI; 107030U (2018) https://doi.org/10.1117/12.2310201
Event: SPIE Astronomical Telescopes + Instrumentation, 2018, Austin, Texas, United States

Abstract

Scientists at the Starfire Optical Range have been researching mesospheric sodium beacons for adaptive optics since 1992. Since then, we have developed four different sodium-wavelength lasers, all of which were based on diode-pumped, sum-frequency Nd:YAG oscillators. In 2016 we combined light from two commercial sodium-wavelength lasers, which use resonant-frequency doubling of light from a Raman fiber-amplifier, to form a single beacon. We used standard polarization techniques to combine the two lasers and produce a single beam with both left-hand and right-hand circularly polarized light. To avoid competitively pumping sodium atoms of the same velocity class, we tuned each of the lasers slightly off of the peak of the Doppler-broadened sodium line. However, the return flux from this beacon was lower than we expected, even when we accounted for the effect of detuning. In this paper, we propose an explanation for this phenomenon and show results from computer modeling and on-sky tests to support our claim. We believe the sodium atoms, which were optically pumped by the shorter-wavelength laser between the D2a F=2, m=+2 and F=3, m=+3 states, were down-pumped by the longer-wavelength laser to the D2b F=2, m=+2 and F=1, m=+1 states. Thus, these atoms were no longer available for optical pumping, which reduced the efficiency of the lasers in producing return flux. Addendum: We hope to show we can mitigate this effect by increasing re-pumping of the sodium D2b line on the shorter-wavelength laser.

Conference Presentation

Citation Download Citation

Keith Wyman, Lee Kann, Alexander Hamm, Mark Eickhoff, Jack Drummond, Olivia Byrd, and Robert Johnson "Measuring the return flux for a sodium beacon created by combining two laser beams", Proc. SPIE 10703, Adaptive Optics Systems VI, 107030U (10 July 2018); https://doi.org/10.1117/12.2310201

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available