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A Fabry-Perot interferometer (FPI) temperature sensor was proposed by splicing a self-made hollow core anti-resonance fiber (HC-ARF) between two single mode fibers (SMFs). The HC-ARF was 2 mm long and one SMF was 20 mm in length. The SMF end face was coated with an Au film. When temperature varied from 45 °C to 85 °C, a sensitivity of 81.1 pm/°C was obtained at the waveband of 1550 nm∼1555 nm. When temperature varied from 35 °C to 95 °C, a sensitivity of 138.8 pm/°C was obtained at the waveband of 1571 nm∼1581 nm. Theoretical analysis suggested that the sensitivity of this proposed sensor can be easily adjusted by varying the length of the Au-coated SMF via the Vernier effect, which was confirmed by a subsequent experiment where the SMF length was varied from 20 mm to 170 mm. This work offers a simple sensitivity control method, and the proposed sensor is easy to manufacture, compact in structure, and convenient in performance control, which can be applied for a wide range of biological and chemical applications.

In this paper, a carboxymethyl cellulose (CMC)/graphene oxide (GO) composite film-coated humidity sensor was proposed based on thin-core fiber Mach-Zehnder interferometer (TCMZI). A segment of thin-core fiber (TCF) was spliced between two segments of single-mode fiber (SMF), and the TCF cladding was first corroded with hydrofluoric acid and then coated with a layer of CMC/GO film via optical driven deposition method. The relative humidity (RH) sensing characteristics of the sensor were experimentally investigated by observing the wavelength shift of resonant dips in the transmission spectrum, which showed that the CMC/GO composite film-coated TCMZI has good repeatability and stability in the measurement of humidity. A maximum average humidity sensitivity of −75.6 pm/%RH was obtained in the RH range of 35%-80%, nearly 2.048 and 3.237 times higher than that of CMC and GO single film coated ones. To the best of our knowledge, this is the first report on using the CMC/GO composite film for humidity measurement, and its excellent performance is expected to be extended to humidity sensitization of more fiber-optic sensors. The proposed sensor has the advantages of simple structure, easy fabrication, low cost, good stability and high performance, which can be applied to the fields of bio-chemical and medicine.

Due to the unique optical properties and good thermal stability, GeAsSeTe microstructured optical fiber (MOF) offers tremendous opportunity for applications in mid-infrared range (MIR). In this article, we design a CS2-filled GeAsSeTe MOF whose core, inner and outer cladding adopt Ge15As25Se15Te45, Ge20As20Se17Te43 and Ge20As20Se15Te45 glass, respectively. Highly efficient four-wave mixing (FWM) is realized and ultrabroadband optical parametric gain is obtained. By analyzing the central parametric gain bandwidth change with the temperature variation, this CS2-filled GeAsSeTe MOF is proved to be highly sensitive concerning temperature sensing, the sensitivity being as high as 2.32nm/°C from −80°C to 45°C. Such high temperature sensing property have key prominence for developing optical fiber temperature sensor in MIR region based on FWM. To the best of our knowledge, this is the first study to propose temperature sensing in the MIR by drawing on central parametric gain bandwidth of FWM change in a GeAsSeTe MOF.

This article presented an investigation of nonlinear temperature sensing based on soliton self-frequency shift (SSFS) in an in-house fabricated microstructured optical fiber (MOF), and the sensing performance was evaluated by detecting the peak wavelength shift of soliton with the variation of temperature. Both theoretical simulation and experimental research were carried out and there was a good correspondence between the two results. The experimental sensitivity was as high as 0.451 nm/°C at 400 mW with a resolution of 0.2653 °C. Our work is a proof of concept of the optical fiber nonlinear phenomenon of SSFS to sensing technology. This temperature sensor does not involve additional fiber modification, and it has potential applications in biomedical, security, and harsh industrial environment.

An ultracompact optical fiber temperature sensor with a fiber-tip structure is proposed and demonstrated based on the Fabry–Perot (FP) interference principle. Composing a tellurite glass microcavity and a commercial multimode fiber, the proposed sensor is fabricated using a simple method of dipping. The theoretical analysis and experimental observation demonstrate that the ambient temperature can be detected by monitoring the wavelength shift of the reflection spectrum. The obtained sensitivity is about 62 pm/°C with linearity of 0.99982 in the range of 20 °C–170 °C. This sensor has great fringe contrast, high linearity, good stability, a wide detection range, and a short response time. It avoids the fusion difficulty between tellurite fiber and silica fiber, and provides a possibility for real-time temperature detection in the biological field and harsh industrial environment.

According to Faraday rotation effect and Fresnel reflection theory, a novel magnetic field intensity sensor is theoretically proposed and experimentally demonstrated by introducing a 6.4-cm-long tellurite (76.5TeO2-6BiO3-11.5Li2O-6ZnO) no core fiber (TBLZ NCF) into the loop of Sagnac interferometer. The large Verdet constant of TBLZ NCF will bring about an apparent Faraday rotation angle in magnetic field sensing, and the large refractive index difference between TBLZ and silica fibers makes the Fresnel reflection more obvious. The designed sensor demonstrates a sensitivity of 13.51 pm/Gs with an accuracy of 1.47 Gs in the measuring range of 0–380 Gs. It has satisfactory linearity, repeatability, and stability, and does not require additional utilization of expensive magnetic field sensitive materials, exhibiting great application potential.

We demonstrate flat supercontinuum (SC) generation in a piece of step-index tellurite fiber pumped by a noise-like mode-locked fiber laser in the deep normal dispersion region. The noise-like pulse emitted from a simple all-fiber mode-locked laser is used as the pump directly and the cascaded stimulated Raman scattering leads to the spectral broadening to the long wavelength region. Flat SC spanning from $\sim 1570$ nm to $\sim 1900$ nm is obtained and no obvious spectral defects are observed. These results show the great advantage of noise-like pulse pumping in the deep normal dispersion region and the potential of noise-like pulse pumped mid-infrared SC generation.

An all-fiber mode-locked laser based on Mamyshev mechanism operating at 1550 nm is demonstrated. Self-phase modulation and offset spectral filtering provide high peak-power pulse selection in the laser cavity and induce mode locking. With selected operating parameters, the all-fiber mode-locked laser easily achieves mode locking without external seed pulses or auxiliary starting arms, making the laser convenient to operate. Pulses with maximum energy ∼18 nJ and width 230 fs are obtained. Pulse width is almost unchanged with increasing pump power, while pulse energy increases linearly. Starting of the mode-locked laser based on Mamyshev mechanism and output spectra with different pump powers are experimentally investigated.

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.

We demonstrate broadband mid-infrared cascaded stimulated Raman scattering (SRS) and flat supercontinuum (SC) generation in a chalcogenide optical fiber made from A s 2 S 5 glass. By using a 2 µm nanosecond laser as the pump source, mid-infrared cascaded SRS up to six orders ranging from 2149 to 3425 nm was experimentally observed, and this all-fiber Raman laser operating at 3.43 µm was realized for the first time to our knowledge. By introducing a 2 µm femtosecond laser as the excited source, the broadband flat mid-infrared SC with the spectral range of ∼ 10 d B (from ∼ 1030 to 3441 nm) was observed. Our results verify that the A s 2 S 5 optical fibers possess promising applications for tunable mid-infrared Raman fiber lasers and SC light sources pumped by 2 µm pulsed lasers.

We demonstrate flat supercontinuum generation in a piece of highly nonlinear fiber pumped with a stable noise-like pulse mode-locked fiber laser. The compact all-fiber laser realizes mode locking based on a nonlinear amplifying loop mirror and emits noise-like mode-locked pulse with high peak power and high average power. The output pulse has a 3-dB bandwidth of ~35.8 nm with the central wavelength of ~1581 nm. Pumping a 102-m highly nonlinear fiber with the noise-like pulse mode-locked fiber laser directly, a flat and weak residual-pump supercontinuum spanning from ~1370 to ~2200 nm is generated. The spectrum within 1865 to 2200 nm contains more than 45% of the whole energy of the supercontinuum.

In this work, we demonstrate a wide-spectrum multi-wavelength fiber laser generated by Brillouin-comb assisted four-wave mixing (FWM). The mechanism of the laser is based on the combination of stimulated Brillouin scattering in cavity and multiple FWM process outside cavity. The experiment results demonstrate that Brillouin-comb assisting is an effective method to improve the FWM process and increase the line number. More than 110 lines are achieved in 10 nm spectral range with the wavelength spacing of ∼ 0.09 nm. The multi-wavelength fiber laser exhibits good stability on both the operating wavelengths and output power. The tunability of this multi-wavelength fiber laser is improved significantly by inserting a tunable filter in the cavity. The total line number is kept more than 110 in the whole tunable range of 30 nm from 1540 to 1570 nm.

In this paper, we proposed a highly sensitive temperature sensor based on self-phase modulation (SPM) in an in-house fabricated microstructured optical fiber (MOF) which had three rings of air holes. The temperature sensing performance was evaluated by detecting the 3 dB bandwidth of SPM spectrum with the variation of temperature at different pump wavelengths and average pump power. At the pump wavelength of 1400 nm with the average pump power of 600 mW, the temperature sensitivity was obtained to be as high as 1.296 nm/°C. Moreover, the theoretical simulation was carried out, the results of which corresponded well with the experiment. To the best of our knowledge, this is the first experimental study concerning SPM-based temperature sensing. This work proves experimentally and theoretically a new temperature sensing mechanism drawing on the SPM effect in optical fibers, which is expected to develop temperature sensors of low cost, simple structure and high sensitivity.

Fiber optical parametric amplifiers (FOPAs) have attracted much attention than conventional optical amplifiers due to their wider operating wavelength ranges. By expanding the FOPA gain bandwidth towards the mid-infrared region, which can only be obtained by using highly nonlinear chalcogenide fibers, more interesting applications in spectroscopy, sensing, biology and metrology can be realized. Chalcogenide hybrid microstructured optical fibers (chalco HMOFs) with buffer layer demonstrated by our group showed good FOPA performance from 3 to 10 μm. However, their tiny and symmetric structures of air holes are difficult to fabricate. To overcome, chalcogenide all solid HMOFs (chalco ASHMOFs) with 6 low-index rods in the cladding were studied in this work using As2Se3, AsSe2 and As2S5 glasses. Moreover, to obtain high birefringence which is necessary to minimize detrimental effects such as, polarization mode dispersion, polarization noise and instability and polarization-maintaining, the symmetry of the fiber was broken by enlarging a pair of solid rods. Numerical analyses show that chalco ASHMOFs can provide near-zero and flattened chromatic dispersion (

We experimentally demonstrate transverse Anderson localization of mid-infrared light by using a transversely disordered optical fiber made of chalcogenide glasses.

We demonstrate ultra-flattened (less than 1ps/km.nm) and near-zero chromatic dispersions profiles which can be tailored with high freedom by using our proposed chalcogenide all-solid hybrid microstructure optical fibers.

In this paper, we reported a multi-wavelength third-harmonic generation (THG) induced by supercontinuum (SC) in an in-house fabricated suspended-core microstructured optical fiber (MOF). The adjustment of pump wavelength and pump power exerted an influence on SC which simultaneously emitted third harmonic (TH) waves in the visible light range. At the pump wavelength of 1220 nm and the average pump power of 450 mW, a multi-wavelength TH spectrum (373∼589 nm) with over twenty distinct peaks was observed under the phase matching (PM) condition between the fundamental mode and the higher-order modes. To the best of our knowledge, this is the first report on THG in optical fibers with so great a number of wavelengths. The maximal THG conversion efficiency ∼6.791 × 10−4 was obtained at 1480 nm, 350 mW, which is highly competitive compared with the values reported previously. Furthermore, theoretical simulation has been carried out, which corresponded well with the experimental observation. This multi-wavelength THG in the suspended-core MOF may provide a unique pathway towards tailored multi-wavelength ultrafast light sources for applications in sensing and imaging technologies.

A double-clad single-mode tellurite optical fiber (DC-SMTOF) with a loss of 0.5 dB/m @1545.1 nm was fabricated based on the TeO2–ZnO–Li2O–Bi2O3 (TZLB) material. During the fiber drawing process, a low level of residual birefringence was produced, which gave a chance for the investigation of the polarization modulation instability (PMI). With a nanosecond laser operated at 1545.1 nm as the pump source, the PMI effect in the DC-SMTOF was investigated using different fiber length and different average pump power. This investigation of the PMI generation in non-silica optical fibers may provide guidance for the generation of the highly repetitive optical pulse train.

Due to the air-guiding characteristics of the air-core, hollow-core optical fibers (HCOFs) can give rise to many potential applications including optical data transmission, terahertz propagation, power beam delivery for industrial applications such as cutting, welding, and engraving, medical applications and chemical sensing. In this work, tellurite HCOFs which have 6 air holes in the cladding and a large hollow core in the center are studied. By numerical analysis, it was realized that the confinement loss in the core will be high when the gap between two nearby cladding air -holes is large or when they connect to each other. The light propagation and transmission properties were demonstrated experimentally from 0.4 to 4.0 μm. By carefully controlling the coupling conditions, lights were coupled successfully into the air core by the fundamental mode. The transmission spectrum included high transmission bands and low transmission bands alternately due to the effect of resonant reflection and anti-resonant reflection. Due to the current operating range of the laser source, the transmission spectrum was measured up to 3.9 μm. But, it is expected to extend to the mid-IR range around 6 μm as shown in the calculation. When the input light at 2.1 μm was linearly polarized, the polarization was maintained in the fiber because the fundamental mode was dominant and the coupling efficiency of the 1st order mode was very weak.

Supercontinuum (SC) has been applied in many applications such as optical coherence tomography, high-precision spectroscopy and frequency metrology [1]. SC can be generated in highly nonlinear fibers by launching high intensity laser pulses into these fibers. The dynamics of SC generation (SCG) closely relates to the chromatic dispersion of the fibers [2]. In the normal dispersion regime, the spectrum broadening dynamics is mainly based on self phase modulation and optical wave breaking which are self-seeded processes. Thus, the output SC preserves its high coherence. Highly coherent and broadband mid-infrared SCG in the all-normal dispersion regime was demonstrated by pumping at 8, 10, and 12 μm [3]. However, only few laser sources are able to provide such long wavelengths. Moving the pumping laser wavelengths to around 1.5 or 2 μm will be more attractive because many commercial fiber lasers are available. In this report, we propose a novel tellurite fiber for supercontinuum generation with a pumping laser at 2 μm. The fiber is obtained by adding six solid rods around the core of a step-index fiber. Such fiber is called all-solid hybrid microstructured optical fiber (ASHMOF). The fiber possesses flattened chromatic dispersion from 2 to 4 μm. Successful fabrication of the ASHMOF was done with an in-house drawing tower. Using a laser pumping at 2 μm into the ASHMOF, highly coherent and high spectral flatness supercontinuum spanning a range from 1.4 to 3.0 μm at - 20 dB level was experimentally generated. Such broad and highly coherent SC will be valuable for applications as optical coherence tomography, ultrafast transient absorption spectroscopy, etc.

The mid-IR supercontinuum generation has attracted much attention during the recent years because many unique molecular absorption bands of most of the molecules exist in this domain. Additionally, mid-IR supercontinuum light sources are expected to have potential applications including astro-photonics, bio-photonic diagnostics, nonlinear spectroscopy, infrared imaging and sensing. For high spatial resolution imaging a spatially coherent supercontinuum light source is desirable. The soft-glass optical fiber is the promising medium for the design and development of a high spatially coherent mid-IR light source with the high brightness. Earlier, the broadband mid-IR supercontinuum generation has been reported using the optical fibers in different materials including tellurite, and chalcogenide, but, its coherence property has not been demonstrated extensively. In this work, we experimentally demonstrate the mid-IR supercontinuum spectrum spanning ⁓1.6 μm to 3.7 μm using a 3 cm long tapered chalcogenide step-index optical fiber pumped with femtosecond laser pulses at 2.6 μm. To justify the experimentally obtained results, a numerical simulation also carried out for the same fiber and pulse parameters. The measured supercontinuum spectrum matches well with the simulated spectrum and generated supercontinuum spectrum is highly coherent within the whole spectral range of the supercontinuum generation.

High peak power mode locked fiber lasers are effective tools for many applications like optical metrology, biomedical imaging, micromachining and so on. All-fiber architecture and high pulse energy mode locked fiber lasers are very attractive to these applications due to their compactness and robustness. In recent years, an attractive mode-locking scheme based on Mamyshev regenerator was demonstrated to realize high pulse energy mode locked pulse output leading to breakthroughs in the mode locked fiber laser performance. We experimentally demonstrate an all-fiber linear Mamyshev regenerator operating at 1550 nm. Self-phase modulation and off-set spectral filtering provide high peak power pulse pick-up effect in the laser cavity and impel the laser to operate in the mode locking regime. With properly setting of the parameters, the all-fiber Mamyshev regenerator can achieve self-starting of the mode locking easily. No external pulse seeds or auxiliary starting arms are needed for the self-starting of the mode locking, which makes the laser very convenient to operate. Pulses with maximum energy of ~18 nJ and pulse width of 230 fs were achieved. The pulse width almost keeps unchanged with increasing in the pump power and the output power increases almost linearly with the pump power. The spectra from the two outputs with different pump powers were experimentally investigated as well. This high pulse energy Mamyshev regenerator can be used as a high quality and cost-effective laser source for many applications.

We proposed new chalcogenide all-solid hybrid microstructured optical fibers which provide flattened normal chromatic dispersion over a wide range from 4.5 to 13 pm and high phase birefringence up to 2.5x10-3 at 12 pm.

Spontaneous four-wave mixing in a novel tellurite fiber is demonstrated. Using a pumping laser at 1.9 um, a signal and an idler at 1.25 and 4.1 um are generated. This corresponds to a frequency shift of 85 THz which is the largest frequency shift in soft-glass fiber ever reported.

Cascaded cross-phase modulation instability (XPMI) is experimentally observed in the normal dispersion regime of a birefringent tellurite microstructured optical fiber (BTMOF). At the average pump power of ~33 mW, cascaded XPMI with nine stokes sidebands and six antistokes sidebands is observed in a 3-m BTMOF. To the best of our knowledge, this is the first demonstration of cascaded XPMI in nonsilica optical fibers. The influence of fiber length variation on the evolution of cascaded XPMI is investigated by using a 0.3-m BTMOF. At the same pump power, cascaded XPMI with only eight stokes sidebands and five antistokes sidebands is observed. This is because shorter fiber length leads to lower nonlinear effect, which in turn induces less obvious XPMI effect.

Aiming at maintaining the chromatic dispersion properties and fiber optical parametric amplification (FOPA) performance when fiber core fluctuation occurs, we propose a buffer step-index optical fiber. The AsSe2 chalcogenide glass is employed as the core material due to its high nonlinearity and broad transmission spectrum. The calculated results in this study show that the chromatic dispersion variation due to the change of core diameter can be greatly suppressed and a continuous and very broad FOPA signal gain spectrum can be obtained and maintained by carefully controlling the core, buffer and cladding properties such as refractive index and diameters. The calculated results in this study showed that by using the proposed 3-cm-long fiber pumped at 5.02 µm, a broad signal gain bandwidth from 3 to 14 µm at about 15 dB is attainable although the fiber core diameter Dc drastically fluctuated from 2 to 5 µm and the buffer diameter Db varies from 8.9 to 9.3 µm. Moreover, when Dc varies in smaller range from 3 to 4 µm, the FOPA signal gain spectra calculated at different fixed values of Db in the range from 8.9 to 9.3 µm are highly maintained. When Db is kept at 9.0 µm and Dc varies from 3 to 4 µm, the calculated FOPA signal gain spectra at different pump wavelengths from 4.98 to 5.02 µm are also nearly identical in the wavelength range from 3 up to 13 µm.

The evolution Raman effect in a single-mode tellurite fiber (SMTF) was investigated by pumping a nanosecond laser operated at ~1545 nm. With the increase of the average pump power, inverse Raman scattering (IRS) effect was first observed in a 2.5-m-long SMTF, which induced a steadily growing second-order Raman Stokes that finally exceeded the first-order Raman Stokes. When the length of the SMTF was reduced to 0.5 m, no IRS effect was obtained due to the lower Raman gain.

It is shown that chalcogenide double-clad fibers (Ch-DCFs) have large potential to realize the highly coherent mid-infrared (MIR) supercontinuum generation. We design the Ch-DCFs with flatter chromatic dispersion and smaller effective mode diameter than chalcogenide step index fibers in the MIR region. We numerically investigate MIR supercontinuum generation in designed Ch-DCFs. It is numerically demonstrated that highly coherent MIR supercontinuum extending from 3.3 to 10.4 μm in the Ch-DCFs can be generated by pumping with hyperbolic secant pulse at 6 μm, the peak power of 2 kW, and the full width at half maximum of 300 fs.

The optical and acoustic fields of stimulated Brillouin scattering (SBS) and the interaction between them are investigated in the As2S3 chalcogenide suspended-core microstructured optical fibers (MOFs) by the finite-element method (FEM). The optical and acoustic fundamental modes are analyzed at 1550 nm. The core diameters of the MOFs vary from 1.0 to 6.0 μm. For each case, the holes of the MOFs are filled with different materials such as trichlormethane (CHCL3), alcohol and water. When the core diameter is 6.0, 4.5, 3.0, 2.0 and 1.0 μm, the ratios of difference for optical fields are ∼0.66%, 0.97%, 1.48%, 1.94% and 3.55%, respectively, while the ratios of difference for acoustic fields are ∼0.13%, 0.24%, 0.34%, 0.74% and 29.13%, respectively. The overlap factors between optical and acoustic fields are calculated, which change with the core diameter and the filled material. The results will be helpful to strengthen or suppress the SBS effect in practical applications.

We demonstrated in this work the wavelength conversion performance based on the four-wave mixing process in a new tellurite step-index fiber as short as 1 m. The fiber was pumped by a femtosecond pulsed laser near the zero dispersion wavelength of the fundamental mode which was close to that of the material dispersion in the near-infrared region. When the pump and signal wavelengths were at 1795 and 1434 nm, respectively, the generated idler was obtained at 2400 nm and the conversion wavelength spacing could be as broad as 966 nm. In addition, a 17.5-dB signal gain at 1550 nm and 1.1-dB idler at 1757 nm were obtained when the pump was tuned to 1647 nm.

A step-index tellurite optical fiber with loss ∼0.02 dB/m at ∼1545 nm was fabricated based on TeO2−Bi2O3−ZnO−Na2O glass. With a nanosecond laser operated at ∼1545 nmas the pump source, second-harmonic generation (SHG) was observed in the 2.5 m tellurite fiber with conversion efficiency up to ∼1.15% at 20 mW, which, to the best of our knowledge, is the highest for non-silica optical fibers. The experimental phenomenon can be explained by the χ(2)-induced model of nonlinear polarization at the core–cladding interface. Furthermore, it can also be explained by a χ(3)-induced model via the four-wave-mixing effect, where a quasi-SH signal and a millimeter wave were generated simultaneously. This new model may help shed light on the physical mechanism of SHG in optical fibers.

We systematically investigate the effect of chromatic dispersion on supercontinuum generation in tellurite all-solid hybrid microstructured optical fibers. Highly coherent and broad supercontinuum from the near to mid-infrared region can be generated in the designed fibers.

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.

Stimulated Raman scattering (SRS) is a nonlinear effect in the media which can transfer a fraction of power from one optical field to another and whose frequency is downshifted by an amount determined by the vibrational modes of the medium [1, 2]. When Raman gain of the optical fiber is high and pump power into it is sufficient, cascaded SRS effect can be achieved [3, 4]. In this paper, a low-loss chalcogenide optical fiber was designed and fabricated based on A S -S glass, and a 16 m long fiber was experimentally used to enhance Raman gain for boosting cascaded SRS generation. A nanosecond laser at ∼1545 nm was used as the pump source and mid-infrared cascaded SRS up to eight orders was observed.

We report a tellurite all-solid hybrid microstructured fiber with ultra-small chromatic dispersion fluctuation which has the potential as mid-infrared fiber optical parametric amplifier medium.

Mid-IR supercontinuum generation has attracted lot of attention in recent years because many unique molecular absorption bands exist in this region [1], Additionally, mid-IR supercontinuum light sources are expected to have potential applications including bio-photonic diagnostics, nonlinear spectroscopy, and infrared imaging [2–4], For high-spatial-resolution imaging a spatially coherent supercontinuum light source is desirable. The optical fiber is the promising medium for the design and development of a highly spatially coherent mid-IR light source with the high brightness. Earlier, the broadband mid-IR supercontinuum generation has been reported using the optical fibers in different materials including tellurite, and chalcogenide, but, its coherence property has not demonstrated extensively. Recently, our group has demonstrated coherent mid-IR supercontinuum generation in step-index tellurite, tapered tellurite, and chalcogenide double clad fibers pumped with femtosecond laser [5–7].

A linear mode-locked fiber laser based on the semiconductor saturable absorption mirror was demonstrated to realize mode locking in group velocity locked vector soliton regime and polarization rotation vector soliton regime. The highly fixed birefringence was introduced into the linear fiber laser cavity by using a piece of polarization maintaining Erdoped fiber. The vector nature of pulse of the mode-locked fiber laser was experimentally studied. It turned out that, this birefringence enhanced mode-locked fiber laser can generate both group velocity locked vector soliton and polarization rotation vector soliton though slightly changing the birefringence of the laser cavity. The experimental results reveal the fundamental physics of group-velocity locked vector soliton and polarization rotation vector soliton generation and demonstrate that the linear birefringence enhanced fiber laser is a good platform for investigating the vector soliton.

Chromatic dispersion controlling is crucial in designing practical optical communication systems, and nonlinear systems. Ultra-flattened chromatic dispersion has been numerically performed in silica photonic crystal fibers (PCFs) whose chromatic dispersion variation can be as small as ±0.5 ps/km/nm. However, keeping arrays of air holes at precise sizes and shapes is highly required to realize the targeted dispersion. Consequently, this requires much effort in controlling air pressure during fiber fabrication and is considered as a disadvantage of PCFs. In this report, we propose a novel fiber structure for flexible controlling of chromatic dispersion. The fiber structure is obtained by adding six solid rods around the core of a step-index fiber. Ultra-flattened and close-to-zero chromatic dispersion can be realized by using this fiber structure. The variation of chromatic dispersion from 2.5 to 3.7 μm is as small as 0 ± 0.2 ps/km/nm. Using a laser pumping at 2 μm into a 5-cm-long fiber, highly coherent supercontinuum (1.2 – 3.3 μm at -20 dB level) is experimentally generated.

The mid-infrared (mid-IR) spectral region is very important topic of research because the molecular fingerprint of most of the molecules find in this region. Therefore, the mid-IR supercontinuum has been of great interest for the application of spectroscopic chemical sensing, metrology, and hyper-spectral imaging. Presently available mid-IR light sources such as optical parametric oscillators, quantum cascade lasers, thermal emitters and synchrotron radiation are not suitable for such mid-IR applications where we require broadband, spatial coherence, portable and high brightness of laser sources. Supercontinuum generation using the optical fibers has been one of the prominent approaches to obtain broadband mid- IR light sources. In this work, we have numerically investigated an all-normal dispersion engineered tapered tellurite step-index fiber structure for the generation of coherent supercontinuum spectrum in the mid-IR region. Supercontinuum spectrum spanning 1.04 – 4.34 μm is obtained by 200 fs laser pulse pumping of coupled peak power of 44 kW at 2.0 μm. Broadband and coherent mid-IR supercontinuum light is generated in a 4 cm long tapered step-index tellurite fiber. Coherent mid-IR supercontinuum spectrum reported in this work is expected to have potential applications for a variety of important applications in various fields including imaging, early cancer detection, sensing, and precision spectroscopy.

We performed numerical analysis of the propagation characteristics of transversely disordered optical fibers with random hexagonal As2Se3 and AsSe2 rods for infrared light in the wavelength of 1-10 μm using beam propagation method and finite element method. Local confinement by random refractive index distribution was observed in both methods. It was revealed that the beam diameter is minimal around a hexagonal rod pitch of 0.8 times of the wavelength.

A new tellurite HC-PCF with non-touching circular cladding air-holes was demonstrated in this work. Its measured transmission spectrum included high and low transmission bands which located from 2.0 up to 4.0 µm.

We propose chalcogenide all-solid hybrid microstructured optical fibers for mid-infrared supercontinuum generation pumped with lasers at short wavelengths. The supercontinuum spectra are from 1.3 to 7 µm and highly coherent.

The accuracy of the surface plasmon resonance (SPR) optical fiber sensor is affected by the change of ambient temperature. Therefore, we propose a simple dual channel SPR optical fiber sensor, which can measure both glucose concentration and ambient temperature. The proposed sensor is a two-channel structure based on a no-core optical fiber (NCF): one channel is coated with gold film and polydimethylsiloxane (PDMS) to sense the ambient temperature, and the other is coated with silver film to sense glucose concentration. The experimental results show that the sensor’s sensitivity for sensing glucose concentration is 2.882 nm / %, and for sensing temperature is -2.904 nm / °C. By monitoring the real-time temperature, the accuracy of glucose concentration detection was improved. The proposed sensor has a simple and compact structure, and it is suitable for sensing glucose solution or other analyte solutions that need temperature compensation.

We design and fabricate a silica optical fiber doped with yttrium aluminosilicate (YAS, Y 2 O 3 –Al 2 O 3 –SiO 2 ) nanoparticles in the core. The optical fiber is drawn directly from a silica tube with YAG (Y 3 Al 5 O 12 ) ceramics and silica powders (the molar ratio 1:18) in the core at the temperature of ∼1950 °C. The YAS nanoparticles are formed during the optical fiber drawing process. Supercontinuum (SC) generation in the optical fiber is investigated at different pump wavelength. At the pump wavelength of ∼1750 nm which is in the deep anomalous dispersion region, SC spectrum evolution is mainly due to multiple solitons and dispersive waves (DWs), and three pairs of multiple optical solitons and DWs are observed. When the pump wavelength shifts to ∼1500 nm which is close to the zero-dispersion wavelength (ZDW), flattened SC spectrum with ±7 dB uniformity is obtained at the wavelength region of ∼990–1980 nm, and only one obvious soliton and DW are observed. At the pump wavelength of ∼1100 nm, a narrow SC spectrum from ∼1020 to 1180 nm is obtained in the normal dispersion region due to self-phase modulation (SPM) effect.

In this work, a low-loss As2S5 optical fiber with 0.1 dB/m at 1545 nm was designed and fabricated, whose residual birefringence provided an opportunity for investigating the polarization modulation instability (PMI). Using a nanosecond laser operated at ∼1545 nm as the pump source, PMI and the stimulated Raman scattering (SRS) were experimentally investigated in a 3 m As2S5 optical fiber. During the SRS process, the amplified CW signal at 1632 nm and 1633 nm induced the PMI. To the best of our knowledge, this is the first report on the PMI effect induced by the amplified signal in the first-order SRS. The PMI gain was measured to be 24.4 dB at the signal of 1551 nm with the pump power of 20 mW, and the Raman gain was measured to be 31.2 dB at the signal of 1632 nm with the pump power of 41 mW. This investigation on the PMI gain and Raman gain in the As2S5 optical fiber may provide a reference for the development of fiber amplifiers, fiber lasers, and optical communication.

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.

We fabricate a dispersion-engineered A s 2 S 5 microstructured optical fiber for demonstration of frequency conversion in one of the atmospheric-transparent windows in the mid-infrared domain. The experimentally obtained results show that parametric wavelength conversion at 4.5 µm is obtained using fabricated microstructured optical fiber pumped with 200 fs laser pulses of average power of 20 mW at 2 µm. Obtained detuning frequency from the pump frequency was ∼ 84 T H z . To the best of our knowledge, the mid-infrared wavelength conversion at 4.5 µm in fiber configuration has been demonstrated for the first time. The experimentally observed result matches well with numerically simulated phase-matching conditions.