Near-infrared optical image transport through an all-solid tellurite optical glass rod with transversely-disordered refractive index profile.

For the first time, an all-solid tellurite optical glass rod with a transversely disordered refractive index profile was fabricated successfully as a medium to study the transverse localization of light and near-infrared (NIR) optical image transport. Two tellurite glass compositions of 70TeO2-8Li2O-17WO3-3MoO3-2Nb2O5 (TLWMN) and 75TeO2-15ZnO-5Na2O-5La2O3 (TZNL) which have a small difference in softening temperature (about 0.5 °C), compatible thermal expansions from room to 400 °C and broad transmission range from about 0.4 up to 6.0 µm were developed for a successful fabrication process. The tellurite transversely disordered optical rod (TDOR) consists of high and low-index units (TLWMN and TZNL, respectively). The diameter of each unit is 1.0 µm and their refractive index difference was about 0.095 at 1.55 µm. Experimental results showed that after a CW probe beam at 1.55 µm propagated in a 10-cm-long tellurite TDOR, the beam became localized. In addition, NIR optical images at 1.55 µm of numbers on a test target were transported. The captured images at the output facet of the tellurite TDOR are visually clear with high contrast and high brightness. The quality of our transported optical images can be comparable or higher than the results which were obtained by a polymer Anderson localized fiber and by a commercially available multicore imaging optical fiber.

Coherent midinfrared supercontinuum generation using a rib waveguide pumped with 200 fs laser pulses at 2.8 µm.

A rib waveguide structure in As2Se3 chalcogenide glass has been designed and numerically analyzed for on-chip coherent supercontinuum generation in the midinfrared region. The waveguide structure possesses an all-normal dispersion profile with dispersion value of -13.22 ps/nm·km at the pump wavelength. Coherent midinfrared supercontinuum spectrum spanning 1.2 to 7.2 µm has been obtained using a 2.5 mm long rib waveguide when pumped with 200 fs laser pulses of a peak power of 2.5 kW and a repetition rate of 1 kHz at 2.8 µm. Such highly nonlinear subwavelength size rib waveguide structures are highly applicable for the power efficient on-chip midinfrared coherent supercontinuum sources. Coherent midinfrared supercontinuum sources are very important in frequency metrology, nonlinear microscopy, nondestructive testing, molecular spectroscopy, and optical coherence tomography.

Highly coherent supercontinuum in the mid-infrared region with cascaded tellurite and chalcogenide fibers.

We numerically investigate two-step supercontinuum (SC) generation using cascaded tellurite and chalcogenide fibers with all-normal group velocity dispersion pumped by a femtosecond laser at 2 µm. The optimized tellurite fiber is a hybrid microstructured optical fiber with a core surrounded by 12 rods. It has flat normal chromatic dispersion from 2 to 5 µm. The chalcogenide fiber is a double-core fiber with flat normal chromatic dispersion from 4 to 10 µm. The output SC spectrum from the best candidate fibers spans from 0.78 to 8.3 µm with coherence of unity all over the spectrum. Such high coherence pulse with broad spectrum will be valuable for many applications in tomography, ultrafast transient absorption spectroscopy, etc. The proposed fiber structures are all-solid and are feasible for fabrication with the common rod-in-tube method. This implies that two-step SC is a potential way to obtain broad, highly coherent SC in the mid-infrared.

Coherent mid-infrared supercontinuum generation in all-solid chalcogenide microstructured fibers with all-normal dispersion.

We report the coherent mid-infrared supercontinuum generation in an all-solid chalcogenide microstructured fiber with all-normal dispersion. The chalcogenide microstructured fiber is a four-hole structure with core material of AsSe2 and air holes that are replaced by As2S5 glass rods. Coherent mid-infrared supercontinuum light extended to 3.3 µm is generated in a 2 cm long chalcogenide microstructured fiber pumped by a 2.7 µm laser.

Mid-infrared supercontinuum generation spanning 2.0 to 15.1 µm in a chalcogenide step-index fiber.

We experimentally demonstrate mid-infrared (MIR) supercontinuum (SC) generation spanning ∼2.0 to 15.1 µm in a 3 cm-long chalcogenide step-index fiber. The pump source is generated by the difference frequency generation with a pulse width of ∼170 fs, a repetition rate of ∼1000 Hz, and a wavelength range tunable from 2.4 to 11 µm. To the best of our knowledge, this is the broadest MIR SC generation observed so far in optical fibers. It facilitates fiber-based applications in sensing, medical, and biological imaging areas.