Samuel Halverson

Optical fiber modal noise in the 0.8 to 1.5 micron region and implications for near infrared precision radial velocity measurements

Modal noise in fibers has been shown to limit the signal-to-noise ratio achievable in fiber-coupled, high-resolution spectrographs if it is not mitigated via modal scrambling techniques. Modal noise become significantly more important as the wavelength increases and presents a risk to the new generation of near-infrared precision radial spectrographs under construction or being proposed to search for planets around cool M-dwarf stars, which emit most of their light in the NIR. We present experimental results of tests at Penn State University characterizing modal noise in the far visible out to 1.5 microns and the degree of modal scrambling we obtained using mechanical scramblers. These efforts are part of a risk mitigation effort for the Habitable Zone Planet Finder spectrograph currently under development at Penn State University.

An Efficient, Compact, and Versatile Fiber Double Scrambler for High Precision Radial Velocity Instruments

We present the design and test results of a compact optical fiber double-scrambler for high-resolution Doppler radial velocity instruments. This device consists of a single optic: a high-index

Suppression of Fiber Modal Noise Induced Radial Velocity Errors for Bright Emission-line Calibration Sources

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The Habitable-zone Planet Finder: A status update on the development of a stabilized fiber-fed near-infrared spectrograph for the for the Hobby-Eberly telescope

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Scrambling and modal noise mitigation in the Habitable Zone Planet Finder fiber feed

2 ball lens that exchanges the near and far fields between two fibers. When used in conjunction with octagonal fibers, this device yields very high scrambling gains and greatly desensitizes the fiber output from any input illumination variations, thereby stabilizing the instrument profile of the spectrograph and improving the Doppler measurement precision. The system is also highly insensitive to input pupil variations, isolating the spectrograph from telescope illumination variations and seeing changes. By selecting the appropriate glass and lens diameter the highest efficiency is achieved when the fibers are practically in contact with the lens surface, greatly simplifying the alignment process when compared to classical double-scrambler systems. This prototype double-scrambler has demonstrated significant performance gains over previous systems, achieving scrambling gains in excess of 10,000 with a throughput of

Development of a new, precise near-infrared Dopplerwavelength reference: a fiber Fabry-Perot interferometer

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A comprehensive radial velocity error budget for next generation Doppler spectrometers

87% using uncoated Polymicro octagonal fibers. Adding a circular fiber to the fiber train further increases the scrambling gain to

Environmental control system for Habitable-zone Planet Finder (HPF)

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A VERSATILE TECHNIQUE to ENABLE SUB-MILLI-KELVIN INSTRUMENT STABILITY for PRECISE RADIAL VELOCITY MEASUREMENTS: TESTS with the HABITABLE-ZONE PLANET FINDER

20,000, limited by laboratory measurement error. While this fiber system is designed for the Habitable-zone Planet Finder spectrograph, it is more generally applicable to other instruments in the visible and near-infrared. Given the simplicity and low cost, this fiber scrambler could also easily be multiplexed for large multi-object instruments.