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All-Fiber Variable-Pressure Gas Cell
Femtosecond laser drilling is used to produce a variable-pressure fiber gas cell. Tightly focused laser pulses are used to produce micrometer-diameter radial channels in a hollow-core photonic band-gap fiber (HC-PBGF), and through these microchannels the core of the fiber is filled with a gas. The fiber cell is formed by fusion splicing and sealing the ends of the HC-PBGF to standard step-index fiber. As a demonstration, acetylene is introduced into an evacuated fiber at multiple backing pressures and spectra are measured.
(a) Experimental setup for laser-drilling. Index-matching fluid is continously pumped through the fiber in an effort to eliminate optical aberrations and scattering along with removing debris from the forming microchannel. (b) Schematic showing the drilling orientation for HC-PBGF. The fiber is translated at a rate of 1micron/s down through the focus of the femtosecond laser.
Scanning electron microscope image of hollow-core photonic band-gap fiber after femtosecond laser drilling of microchannel. The diameter of the formed channel is 1.5 microns.
C. J. Hensley, D. H. Broaddus, C. B. Schaffer, and A. L. Gaeta, "Photonic band-gap fiber gas cell fabricated using femtosecond laser micromachining,"
Opt. Express 15 6690-6695 (2007). PDF
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