Resonant Optical Interactions with Molecules Confined in Photonic Band-Gap Fibers

We investigate resonant nonlinear optical interactions and demonstrate induced transparency in acetylene molecules in a hollow-core photonic-band-gap fiber at $1.5\mu \mathrm{m}$. The induced spectral transmission window is used to demonstrate slow-light effects, and we show that the observed broadening of the spectral features is due to collisions of the molecules with the inner walls of the fiber core. Our results illustrate that such fibers can be used to facilitate strong coherent light-matter interactions even when the optical response of the individual molecules is weak.

Figure 1

Schematic diagram of the experimental setup. The transverse cross section of the HC-PBF is also shown. EDFA: erbium-doped fiber amplifier; TSL: tunable semiconductor laser; FPC: fiber-polarization controller; PBC: polarization-beam combiner; L: lens.

Figure 2

(a) Measured (points) and theoretical (line) Doppler-broadened absorption spectra for the $R(15)$ transition in acetylene within a 1.3-m segment of photonic-band-gap fiber. A diagram of the relevant molecular levels is shown in the inset. (b) Measured (points) and theoretical (line) spectra for the same transition in the presence of a strong control beam (320 mW at the fiber output).

Figure 3

(a) Experimental (circles) and theoretical (lines) relative transparencies (ratio of the change in the zero-detuning probe transmission in the presence of the control beam to the zero-detuning probe transmission without the control beam) as functions of control power measured at the output of the fiber. (b) The corresponding width (FWHM) of the transparency dip.

Figure 4

Normalized amplitude vs time for a probe pulse with (delayed) and without (normal) the control beam. The inset shows a close-up of the pulse peaks. See text for measurement details.