Supercontinuum generation in a chalcogenide all-solid hybrid microstructured optical fiber.

We report the fabrication of a chalcogenide all-solid hybrid microstructured optical fiber and its application in supercontinuum generation for the first time, to the best of our knowledge. The fiber possesses all-normal and flattened chromatic dispersion, making it highly potential for broad and coherent supercontinuum generation. By pumping the fiber with a femtosecond laser at 3, 4, and 5 µm, broad supercontinua with good spectral flatness are generated. The broadest SC spectrum extending from 2.2 to 10 µm at -20 dB level was obtained when the fiber was pumped at 5 µm with an input power of 3.9 mW.

Intracavity supercontinuum generation in a mode-locked erbium-doped fiber laser based on the Mamyshev mechanism with highly nonlinear fiber.

An all-fiber supercontinuum laser source with a piece of highly nonlinear fiber inserted into a mode-locked fiber laser is experimentally demonstrated. This laser achieves mode-locking based on the Mamyshev mechanism and realizes supercontinuum generation spanning from 1330 nm to 2030 nm directly. Mode-locking based on the Mamyshev mechanism can be obtained easily, and the influence of the parameters of the laser cavity on the supercontinuum laser source is investigated. This supercontinuum laser source has a simple structure, and no amplifier stages are required. It demonstrates intracavity supercontinuum generation in mode-locked fiber laser based on the Mamyshev mechanism and exploits its operation further.

Coherent Mid-IR Supercontinuum Generation using Tapered Chalcogenide Step-Index Optical Fiber: Experiment and modelling.

Mid-infrared region of electromagnetic spectrum has increased a lot of scientific and technical interest because of its utility to figure out the molecular fingerprints. Current mid-infrared light sources including quantum cascade lasers, thermal-emitters, and synchrotron radiation are not suitable for various potential applications where we require coherent, portable and broadband light sources. During the current decade, several efforts have been put forwarded to extend the spectral range of the supercontinuum. However, the coherent mid-infrared supercontinuum spectrum in the mid-infrared region has been demonstrated rarely. Here, we demonstrate a coherent mid-infrared supercontinuum using a tapered chalcogenide fiber pumped at various wavelength ranging from 2 µm to 2.6 µm. Experimental observations show that the supercontinuum spectrum extending from ~1.6 µm to 3.7 µm can be achieved using a 3 cm long tapered chalcogenide step-index optical fiber pumped with femtosecond laser pulses at 2.6 µm. To the best of our knowledge, using short pump wavelengths at 2 µm to 2.6 µm in an all-normal dispersion engineered chalcogenide glass fiber, the coherent supercontinuum spectrum has been reported first time. Such coherent broadband light source has its key prominence for the various prospective applications in the fields of bio-medical, sensing, and multiplex coherent anti-Stokes Raman scattering microspectroscopy.

Tunable and switchable all-fiber dual-wavelength mode locked laser based on Lyot filtering effect.

Mode-locked fiber lasers that generate two frequency combs with different frequency intervals could find very important applications in low-complexity dual-comb metrology. We report a partially polarization-maintaining all-fiber dual-wavelength dual-comb mode locked laser. The polarization dependent loss of the wavelength division multiplexer combined with the polarization-maintaining fibers leads to the periodic Lyot filtering effect. Traditional single wavelength mode locking can be realized with the tunable central wavelength and spectral shape. By properly setting the state of the polarization controller, stable dual-wavelength asynchronized mode locked pulse trains with the repetition rate difference of hundreds of Hertz can be achieved. In this dual-wavelength mode locked fiber laser, the dispersion of the laser cavity leads to group velocity difference of the two mode locked pulse trains with different central wavelengths, which results in the generation of dual-comb output with the frequency difference of hundreds of Hertz. The central wavelengths of the dual-wavelength mode locked fiber laser are demonstrated to be tunable in a certain range as well. Meanwhile, a novel dual-wavelength soliton molecule mode locking is also demonstrated. Such compact all-fiber dual-wavelength dual-comb mode locked laser could find various practical applications that in need of dual-comb fiber laser system.

Tapered tellurite step-index optical fiber for coherent near-to-mid-IR supercontinuum generation: experiment and modeling.

We demonstrate broadband highly coherent near-to-mid-IR supercontinuum generation using a short length of tapered tellurite step-index fiber pumped with an ultrafast laser in normal dispersion regime. The tapered tellurite fiber possesses all-normal dispersion characteristics within the whole range of the generated supercontinuum spectrum. A highly coherent near-to-mid-IR supercontinuum spectrum spanning 1.28 to 3.31 µm at a -40 dB intensity level is obtained using a 3.2 cm long tapered tellurite fiber when it is pumped with a 200 fs laser pulse with a peak power of 19.8 kW at 2 µm. To obtain the supercontinuum spectrum, we also carried out numerical modeling for the tapered tellurite step-index fiber with the same geometrical parameters and pump conditions used in the experiment. The numerical observation supports the experimentally obtained result. The findings of this work show that the fabricated tapered tellurite step-index fiber is a promising nonlinear medium to obtain a coherent near-to-mid-IR supercontinuum spectrum in a short length of the fiber.

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.

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.

Mid-infrared cascaded stimulated Raman scattering up to eight orders in As-S optical fiber.

Mid-infrared cascaded stimulated Raman scattering (SRS) is experimentally investigated in an As-S optical fiber which is fabricated based on As38S62 and As36S64 glasses and whose fiber loss is ∼0.08 dB/m at1545 nm. Using a nanosecond laser operated at ∼1545 nm as the pump source, mid-infrared cascaded SRS up to eight orders is obtained in a 16 m As-S fiber. To the best of our knowledge, this is the first demonstration of SRS of such high order in non-silica optical fibers, and it may contribute to developing tunable mid-infrared Raman fiber lasers using C-band pump sources.

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.

All-optical dynamic photonic bandgap control in an all-solid double-clad tellurite photonic bandgap fiber.

All-optical dynamic photonic bandgap (PBG) control by an optical Kerr effect (OKE) is investigated in an all-solid double-clad tellurite photonic bandgap fiber (PBGF) which is fabricated based on TeO2-Li2O-WO3-MoO3-Nb2O5 (TLWMN, high-index rod) glass, TeO2-ZnO-Na2O-La2O3 (TZNL, inner cladding) glass, and TeO2-ZnO-Li2O-K2O-Al2O3-P2O5 (TZLKAP, outer cladding) glass. To the best of our knowledge, this is the first demonstration of all-optical dynamic PBG control in optical fibers. This PBGF has a high nonlinear refractive index which can lead to a significant OKE and induce the generation of all-optical dynamic PBG control. The transmission spectrum is simulated with the pump peak power increasing from 0 to 300 kW, which shows an obvious PBG shift. Dynamic PBG control is demonstrated both numerically and experimentally at the pump peak power of 200 kW (ON or OFF) at the signal of 1570 nm.

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.

Optical parametric oscillator based on degenerate four-wave mixing in suspended core tellurite microstructured optical fiber.

We report on a suspended core tellurite microstructured optical fiber (TMOF) based optical parametric oscillator (OPO). The intracavity gain is provided by the degenerate four-wave mixing (DFWM) occurred in a 1.5-m-long TMOF synchronously pumped by a mode-locked picosecond erbium-doped fiber laser. The oscillated signal can be generated from 1606 nm to 1743.5 nm, and the idler can be emited from 1526.8 nm to 1395 nm by adjusting the pump wavelength from 1565.4 nm to 1551 nm. A total intenal conversion efficiency of -17.2 dB has been achieved.

Experimental observation of multiple dispersive waves emitted by multiple mid-infrared solitons in a birefringence tellurite microstuctured optical fiber.

We experimentally demonstrate multiple dispersive waves (DWs) emitted by multiple mid-infrared solitons in a birefringence tellurite microstuctured optical fiber (BTMOF). To the best of our knowledge, this is the first demonstration of multiple DWs in the non-silica fibers. By using a pulse of ~80 MHz and ~200 fs emitted from an optical parametric oscillator (OPO) as the pump source, DWs and solitons are investigated on the fast and slow axes of the BTMOF at the pump wavelength of ~1800 nm. With the average pump power increasing from ~200 to 450 mW, the center wavelength of the 1st DW decreases from ~956 to 890 nm, the 2nd DW from ~1039 to 997 nm, the 3rd DW from ~1101 to 1080 nm, and the 4th DW from ~1160 to 1150 nm. Meanwhile, obvious multiple soliton self-frequency shifts (SSFSs) are observed in the mid-infrared region. Furthermore, DWs and solitons at the pump wavelength of ~1400 and 2000 nm are investigated at the average pump power of ~350 mW.

Optical parametric gain and bandwidth in highly nonlinear tellurite hybrid microstructured optical fiber with four zero-dispersion wavelengths.

The parametric amplification gain and bandwidth in highly nonlinear tellurite hybrid microstructured optical fiber (HMOF) are simulated based on four wave mixing process. The fiber core and cladding materials are made of TeO(2)­Li(2)O­WO(3)­MoO(3)­Nb(2)O(5) and TeO(2)­ZnO­Na(2)O­P(2)O(5) glass, respectively. The fiber has four zero-dispersion wavelengths and the chromatic dispersion is flattened near the zerodispersion wavelengths. A broad gain bandwidth as wide as 1200 nm from 1290 to 2490 nm can be realized in the near infrared window by using a tellurite HMOF as short as 25 cm.