Characterization of mid-infrared emissions from C2H2, CO, CO2, and HCN-filled hollow fiber lasers

Abstract

International audienceWe have now demonstrated and characterized gas-filled hollow-core fiber lasers based on population inversion from acetylene (12C2H2) and HCN gas contained within the core of a kagome-structured hollow-core photonic crystal fiber. The gases are optically pumped via first order rotational-vibrational overtones near 1.5 μm using 1-ns pulses from an optical parametric amplifier. Transitions from the pumped overtone modes to fundamental C-H stretching modes in both molecules create narrow-band laser emissions near 3 μm. High gain resulting from tight confinement of the pump and laser light together with the active gas permits us to operate these lasers in a single pass configuration, without the use of any external resonator structure. A delay between the emitted laser pulse and the incident pump pulse has been observed and is shown to vary with pump pulse energy and gas pressure. Furthermore, we have demonstrated lasing beyond 4 μm from CO and CO2 using silver-coated glass capillaries, since fused silica based fibers do not transmit in this spectral region and chalcogenide fibers are not yet readily available. Studies of the laser pulse energy as functions of the pump pulse energy and gas pressure were performed. Efficiencies reaching ~ 20% are observed for both acetylene and CO2

Efficient diode-pumped mid-infrared emission from acetylene-filled hollow-core fiber

“…Using low-loss antiresonant hollow core fibers filled with acetylene, we have demonstrated efficient diode-pumped 3.1-3.2 μm mid-IR emission. The efficiency with respect to the total incident pump power is ~20%, the minimum pump laser energy is <50 nJ, and no saturation of the output pulse energy is seen at our maximum pump energy of 3 µJ, which are substantial improvements over the similar results published previously [20][21][22] using an OPO as pump source. Due to the low transmission loss, large core size and high damage threshold of the antiresonant hollow core fibers, efficient, compact, high-power mid-IR fiber gas lasers can potentially be obtained at a number of wavelengths by properly designing the fiber's transmission bands, and carefully selecting active gases and pump lasers.…”

“…Because we are able to use a long length of low-loss fiber we do not see any saturation of output energy at high pump power, even at low pressure, allowing the highest output energy and highest efficiency to be attained simultaneously. Previous reports [20,21] achieved high conversion efficiency only up to ~1 µJ absorbed pump energy. The total optical-to-optical efficiency could be improved by further suppressing the ASE using a narrow-band filter before the power-amplifier, reducing the pump laser linewidth using more highly doped and shorter erbium fibers in the power-amplifier.…”

“…Owing to the nature of transitions in atomic and molecular gases, fiber gas lasers are spectrally narrow even without additional linewidth limiting measures. Since the first emission in H 2 -filled HC-PCF by stimulated Raman scattering was demonstrated in 2002 [16], fiber gas lasers have been intensively investigated [17][18][19][20][21][22][23][24]. The first mid-IR fiber gas laser was demonstrated in acetylene-filled Kagome structured hollow core fiber in 2011 [20], but the measured slope efficiency was only ~1% because of the high transmission loss of 20 dB/m at laser wavelength.…”

“…The first mid-IR fiber gas laser was demonstrated in acetylene-filled Kagome structured hollow core fiber in 2011 [20], but the measured slope efficiency was only ~1% because of the high transmission loss of 20 dB/m at laser wavelength. By optimizing the fiber structure, the loss was greatly improved to ~5 dB/m, but the power conversion efficiency with the respect to the total incident pump laser power was still low (<10%) [21,22] due to the broad linewidth of the pump source of optical parametric oscillator (OPO). The OPO is bulky and cumbersome, and not suitable for compact laser designs.…”

Hollow-core Optical Fiber Gas Lasers (HOFGLAS): a review [Invited]

“…The pump is coupled into the gas filled fiber from one end, laser output is observed at the other end. Here we review two representative HOFGLAS systems: (i) 12 C 2 H 2 [15,16], and (ii) H 12 C 14 N [43]. Both C 2 H 2 and HCN have strong absorption in the 1.52-1.55 µm region [44,45] and hence are well suited for optical pumping in the fiber optic communication C-band, for example, with Erbium fiber lasers.…”