Dual-mode Emission Research Articles

Ultraviolet- and Near-Infrared-Excitable LaPO4:Yb3+/Tm3+/Ln3+ (Ln = Eu, Tb) Nanoparticles for Luminescent Fibers and Optical Thermometers

The widespread demand for multifunctional materials that can be used for anticounterfeiting purposes, as dual-mode phosphors, or as optical nanothermometers has inspired us to synthesize Yb3+/Tm3+/Ln3+ (Ln = Eu, Tb)-doped LaPO4 nanoparticles (NPs) and, based on these, luminescent fibers that utilize and extend the properties of the NPs. They show intense dual-mode color-tunable emission and temperature-dependent up-conversion (UC) luminescence, which makes them multifunctional and of a high potential applicability. The nanomaterials were obtained by a simple and fast coprecipitation method, yielding pure-phase monoclinic products. The products were used as luminescence activators in cellulose fibers, showing their potential applications for security purposes. They can emit strong UC and down-conversion luminescence within one particle, under excitation of commercially available near-infrared (NIR) and ultraviolet (UV) excitation sources. The pure red and green emissions under UV irradiation resulted from the presence of Eu3+ or Tb3+ ions in the structure of the products, whereas violet-blue emission was obtained under NIR excitation because of Yb3+ and Tm3+ codopants. After simultaneous UV/NIR double-laser excitation, they obtained NPs that show a complex luminescence resulting from Tm3+ (after energy transfer from Yb3+), Tb3+, or Eu3+. The obtained UC emission can be tuned, giving a huge color shift (from orange or green to blue). What is more, thanks to the presence of thermalized levels of Tm3+ ions, these materials can act as promising temperature nanosensors in a wide range of temperatures from 293 to 679 K. Using the fluorescence intensity ratio technique, relatively high thermal sensitivity (Sr) was obtained, 0.024 and 0.022 K–1 for 293 K for the Yb3+/Tm3+/Eu3+ and Yb3+/Tm3+/Tb3+ samples, respectively.

Efficient dual-mode luminescence from lanthanide-doped core–shell nanoarchitecture for anti-counterfeiting applications

Fluorescent anti-counterfeiting technique is generally based on the development of luminescent materials, which generally exhibit single-mode emissions under single-wavelength excitation, thus resulting in a poor anti-fake effect. To improve the anti-forgery performance of fluorescent anti-counterfeiting approaches, dual-mode luminescent nanoparticles with the form of a β-NaGdF4:Yb/Ho/Ce@β-NaYF4:Tb/Eu core–shell structure have been skillfully designed and synthesized by a co-precipitation strategy. Through the cross-relaxation process between Ce3+ and Ho3+ ions in the inner core region, the up-conversion luminescence colors of the as-synthesized samples can be turned from green to yellow and finally to red when adjusting the dopant concentration of Ce3+ in the core. By selecting Ce3+ as the sensitizer for harvesting the energy of incident ultraviolet (UV) light and introducing Gd3+ as the ideal intermediate for subsequent energy migration, the down-converting emission colors of the as-obtained samples are also regulated from green to red via a Gd3+-assisted interface energy transfer processes (Ce3+ → Gd3+ → Tb3+, Ce3+ → Gd3+ → Tb3+ → Eu3+). Consequently, dual-mode luminescence with multi-color outputs can be achieved in the pre-designed core–shell nanostructure under the excitation of a 980 nm near-infrared laser and 254 nm UV light. The designed nanoarchitecture with bright dual-mode emissions and tunable colors greatly improves the ability of modern anti-counterfeiting, demonstrating its promising applications in anti-fake and optical multiplexing.

Preparation and characterization of NaYF4:Er3+,Tm3+@NaYF4:Ce3+,Tb3+ microcrystals with dual-mode emissions at the single-particle level

Under hydrothermal environment, we synthesized lanthanide ions doped sodium yttrium fluoride (NaYF4:Er,Tm@NaYF4:Ce,Tb) luminescent microcrystals via an epitaxial growth technique. The structure and morphology of these microcrystals were examined by SEM, TEM, EDS and XRD measurements. These particles show dual-mode emissions with red upconversion (UC) and green down conversion (DC) as single particles level. The mean length and diameter of these microparticles increase from 0.43 to 2.26 μm and from 1.33 to 1.86 μm, respectively. Most interestingly, the photoluminescence properties of NaYF4:Er,Tm@NaYF4:Ce,Tb phosphor crystals are highly dependent on the crystallite size. The microcrystals fluoresce emit dual-mode emissions when they are solid or dispersed in solvents. Benefiting its intensive fluorescence and uniform morphology, these materials hold great potential for security and anti-counterfeiting applications.

Dual mode (upconversion and downshifting) behavior of Ho3+/Yb3+/Bi3+ co-doped YTaO4 phosphor and its application as a security ink

The Ho3+/Yb3+ co-doped YTaO4 phosphor has been synthesized in absence and presence of Bi3+ ion using high temperature solid state reaction method. X-ray diffraction (XRD) patterns confirm the pure phase formation of the synthesized materials. The vibrational behavior of the samples is studied by Fourier Transform Infrared (FTIR) spectroscopy, which suggests the phonon frequency of the material about 625 cm−1. The direct optical band gap of the synthesized phosphor has been calculated using UV–Vis absorption spectrum and the value is found to be 4.80 eV. However, the value of band gap is reduced in presence of Bi3+ ions (4.26 eV). Ho3+/Yb3+ co-doped YTaO4 phosphor shows intense green and weak red upconversion emissions on 980 nm excitation. Ho3+/Yb3+ co-doped YTaO4 phosphor sample also shows intense green and weak red emissions on 450 nm excitation. The downshifting emission is enhanced two to three times in presence of Bi3+ due to metal to metal charge transfer self activation of the host. However, the UC emission intensity almost remains unchanged even in presence of Bi3+. Bi3+ ion also shows an intense broad blue emission on UV excitation. The Ho3+/Yb3+ co-doped YTaO4 phosphor sample has been used for security ink applications in green region via 980 nm excitations and in blue region in presence of Bi3+ via UV (365 nm) excitation. Thus, the dual mode emission of this phosphor is applicable for security ink applications in two different regions. This material also permits one to get an intense tunable radiation from 350 to 650 nm on excitation with 342 nm. There are very few dye lasers, which emit intense tunable radiation in this wavelength region in such a wide wavelength range.

Dual-mode emission and transmission microscopy for virtual histochemistry using hematoxylin- and eosin-stained tissue sections.

In the clinical practice of pathology, trichrome stains are commonly used to highlight collagen and to help evaluate fibrosis. Such stains do delineate collagen deposits but are not molecularly specific and can suffer from staining inconsistencies. Moreover, performing histochemical stain evaluation requires the preparation of additional sections beyond the original hematoxylin- and eosin-stained slides, as well as additional staining steps, which together add cost, time, and workflow complications. We have developed a new microscopy approach, termed DUET (DUal-mode Emission and Transmission) that can be used to extract signals that would typically require special stains or advanced optical methods. Our preliminary analysis demonstrates the potential of using the resulting signals to generate virtual histochemical images that resemble trichrome-stained slides and can support clinical evaluation. We demonstrate advantages of this approach over images acquired from conventional trichrome-stained slides and compare them with images created using second harmonic generation microscopy.

Dual-Mode Long-Lived Luminescence of Mn2+-Doped Nanoparticles for Multilevel Anticounterfeiting.

Luminescent nanoparticles with dual-mode long-lived luminescence are of great importance for their attractive applications in biosensing, bioimaging, and data encoding. Herein, we report the realization of up- and downconversion emission of Mn2+ dopants in multilayer nanoparticles of NaGdF4:Yb/Tm@NaGdF4:Ce/Mn@NaYF4 upon excitation at 980 and 254 nm, respectively. The dual-mode emission of the Mn2+ dopants at 531 nm have a long-lived lifetime up to ∼30 ms as a result of the spin-forbidden optical transition of Mn2+ within the 3d5 configuration. After ceasing steady excitation at the two wavelengths, the long-lived feature of Mn2+ luminescence allows a longer persistent time than lanthanide emissions, thereby enabling the ease of data decoding by a cell phone camera under a burst mode. The long-lived green upconversion emission also permits the generation of a long green tail emission upon dynamic excitation at 980 nm. These attributes make the as-prepared Mn2+-doped multilayer nanoparticles particularly attractive for multilevel anticounterfeiting.

Performance of a diesel engine run on diesel and natural gas in dual-fuel mode of operation

In view of energy crisis, many types of alternative fuels have been tried all over the world for use in internal combustion (IC) engines. This investigation on the use of natural gas as a substitute fuel is in line with the trend of finding alternative fuels. In this investigation, experiments have been performed to study the performance of a diesel engine with natural-gas-diesel in dual-fuel mode with different diesel proportions of 10-100% in 10% interval. The results show that overall the performance with CNG were lower than 100% diesel operations. At lower loads, the performances were much poorer and higher powers, the performances were much better but still lower than 100% diesel operation. The bsfc at 1.1 kW with 90% CNG operation was 68% higher than 100% diesel operation. However, at 2.8 kW the bsfc at 90% CNG operation was only 7% higher. The exhaust emissions show that in dual-mode, the CO2 and smoke emissions were lower due to lower carbon to hydrogen ratio of CNG. The CO emission was higher due to lower air-fuel ratio as the CNG introduction in the intake air replaced some air in the intake runner.

Multichannel luminescence properties and ultrahigh-sensitive optical temperature sensing of mixed-valent Eu2+/Eu3+ co-activated Ca8ZrMg(PO4)6(SiO4) phosphors

A novel dual-emitting Ca8ZrMg(PO4)6(SiO4): (Eu3+, Eu2+) phosphors with ultrahigh-sensitive optical temperature sensing are prepared by a conventional solid-state method. The Eu2+/Eu3+ co-activated Ca8ZrMg(PO4)6(SiO4) phosphors exhibit efficient dual-mode emissions with an intense, broad blue emission peaked at 414 nm and a relative bright red-emitting centered at 614 nm under 297 nm UV-light excitation, respectively. Furthermore, the fluorescence intensity ratio (FIR) technology is applied to analyse the optical temperature sensing performance of Ca8ZrMg(PO4)6(SiO4): (Eu3+, Eu2+) phosphors. Based on different thermal quenching behavior of Eu2+ and Eu3+ dual-emitting centers, linear temperature-dependent FIR between Eu2+ and Eu3+ is obtained. The maximal absolute sensitivity reaches as high as 5.94% K−1, which is superior to that for the other luminescent temperature sensing materials reported previously. Analyses of the temperature-dependent photoluminescence spectra and configurational coordinate diagrams for Ca8ZrMg(PO4)6(SiO4): (Eu3+, Eu2+) phosphors indicate that the temperature-sensitive variation in FIR of Eu2+ to Eu3+ is originated from the difference in thermal quenching activation energy for 5d→4f transition of Eu2+ and 5D0→7FJ (J = 1, 2, 4) transitions of Eu3+. These results reveal that the Ca8ZrMg(PO4)6(SiO4): (Eu3+, Eu2+) phosphors show glorious potential in high temperature optical thermometry.

Simultaneous Dual-mode Emission and Tunable Multicolor in the Time Domain from Lanthanide-doped Core-shell Microcrystals.

The dual-mode emission and multicolor outputs in the time domain from core-shell microcrystals are presented. The core-shell microcrystals, with NaYF4:Yb/Er as the core and NaYF4:Ce/Tb/Eu as the shell, were successfully fabricated by employing the hydrothermal method, which confines the activator ions into a separate region and minimizes the effect of surface quenching. The material is capable of both upconversion and downshifting emission, and their multicolor outputs in response to 980 nm near-infrared (NIR) excitation laser and 252 nm, and 395 nm ultraviolet (UV) excitation light have been investigated. Furthermore, the tunable color emissions by controlling the Tb3+-Eu3+ ratio in shells and the energy transfer of Ce3+→Tb3+→Eu3+ were discussed in details. In addition, color tuning of core-shell-structured microrods from green to red region in the time domain could be obtained by setting suitable delay time. Due to downshifting multicolor outputs (time-resolved and pump-wavelength-induced downshifting) coupled with the upconversion mode, the core-shell microrods can be potentially applied to displays and high-level security.

The core-shell-structured NaYF4:Er3+,Yb3+@NaYF4:Eu3+ nanocrystals as dual-mode and multifunctional luminescent mechanism for high-performance dye-sensitized solar cells

The core-shell-structured NaYF4:Er3+,Yb3+@NaYF4:Eu3+ (NYFEY@NYFE) nanocrystals with dual-mode emission have been satisfactorily prepared through a solvothermal method utilizing oleic acid and octadecene. From the emission spectra of dual-mode luminescent nanocrystals, it could be seen that nanocrystals consisted of two disparate units, one supplying up-converting luminescence excited with the 980 nm laser and the other providing down-converting luminescence by means of ultraviolet excitation, which are assigned to 4S(3/2) → 4I(15/2) transitions of Er3+ and 5D0 → 7F2 transitions of Eu3+, separately. And then, a novel photoelectrode structure via introducing dual-mode luminescent materials was proposed. The photoelectric conversion efficiency of DSSCs with NYFEY@NYFE photoelectrode attains 7.37%, raised by a factor of 1.37 in comparison to that of the DSSCs without Eu3+ and Er3+ doping. The preparation of dual-mode NYFEY@NYFE not only has great significance to the study of material itself but its application in DSSCs, and can be also applied to other types of solar cells.

Hydrothermal Addition Polymerization for Ultrahigh-Yield Carbonized Polymer Dots with Room Temperature Phosphorescence via Nanocomposite.

Hydrothermal/solvothermal treatments have been widely used to prepare carbonized polymer dots (CPDs) through the condensation and carbonization of small molecules and/or polymers. However, the basic scientific issues, such as the nucleation and growth process, morphology and size control, yield increase, and photoluminescence (PL) mechanism have not been well investigated. In this work, enlightened by the principle of soap-free emulsion polymerization, CPDs with ultrahigh yields (ca. 85 %) were obtained by hydrothermal addition polymerization and carbonization (HAPC) of monomers. The unprecedented initiator-induced addition polymerization was exploited to synthesize CPDs for the first time. As expected in typical emulsion polymerization processes, the developed HAPC method can produce CPDs with designed sizes by systematically regulating the HAPC parameter, uncovering an unprecedented strategy for regulating the size of CPDs. In addition, the obtained CPDs were provided with high photoluminescence quantum yields (PLQY) up to 45.58 %, while the relationship between the photoluminescence (PL) mechanism and chemical structure was investigated. The viscosity parameter was first adopted to measure the polymer property of CPDs. Moreover, the ultrahigh yield and low-cost CPDs elicited the high-performance CPDs/PVA nanocomposite (PVA=poly(vinyl alcohol)) with fluorescence and room-temperature phosphorescence dual-mode emission, demonstrating potential for advanced anti-counterfeit applications.

Tunable green/red dual-mode luminescence via energy management in core-multishell nanoparticles

Achieving up-conversion luminescence from Tb3+/Eu3+ ions was generally via a complicated energy transfer process (Yb3+ → Tm3+ → Gd3+ → Ln3+, Ln = Tb/Eu), which makes the relevant energy management rather difficult and inevitably results in impure blue luminescence of Tm3+. In this work, a facile and rational strategy is designed to integrate dual-mode luminescence from Eu3+/Tb3+ ions into NaGdF4:Yb/Eu@NaGdF4:Ce@NaGdF4:Yb/Tb@NaYF4 core-multishell nanostructure. It is found that the down-conversion energy transfer across NaGdF4@NaGdF4 interface is confined in a narrow space region of approximately 2 nm. For the up-conversion mode, the primary factor that dominates the emission intensity of Eu3+ is determined to be the molar ratio of NaGdF4:Yb/Tb component in the second shell to NaGdF4:Yb/Eu one in the core, which differs from the anisotropic filtration effect previously reported. Eventually, tunable dual-mode emission colors were achieved through simply varying the inner shell thickness of NaGdF4:Yb/Tb. The strategy of integrating dual-mode luminescence of Eu3+/Tb3+ reported here for energy management allows one to design new luminescence materials for many important applications.

Dual-mode emission of single-layered graphene quantum dots in confined nanospace: Anti-counterfeiting and sensor applications

Engineering of the luminescent properties for graphene quantum dots (GQDs) presents two enormous challenges: 1) The bandgap of GQDs is mainly determined by structural defects (size, shape, and the fraction of sp2 and sp3 domains), which results in non-stoichiometric nature; 2) the preparation methods limit the achievement of an accurate chemical structure of GQDs, leading to many controversial explanations over the relationship between the structural defects and bandgaps. Here, single-layered GQDs with an exact structure are obtained by in-situ reaction of intercalated precursors in the confined nanospace of layered double hydroxides (LDHs). Subsequently, the structure-property relationship is uncovered, demonstrating the enhanced fluorescence and activated room temperature phosphorescence of the as-prepared GQDs-LDHs, which originate from synergistic effects: 1) strong confinement provided by the nanospace of LDHs; 2) rich O-containing functional groups on the surface of GQDs resulting from LDH catalysis. Moreover, the colorless nature and dual-emission characteristics of GQDs-LDHs satisfy the preconditions as anti-counterfeiting markers for protecting valuable documents (bank notes, commercial invoices, etc.). Particularly, owing to the low toxicity of GQDs and the edible property of LDHs, the GQDs-LDHs/gelatin capsules could be the new generation of potential green anti-counterfeiting material in the field of food and drugs.

99mTc-Labeled RGD-Polyethylenimine Conjugates with Entrapped Gold Nanoparticles in the Cavities for Dual-Mode SPECT/CT Imaging of Hepatic Carcinoma.

We report the construction and characterization of 99mTc-labeled arginine-glycine-aspartic acid (RGD)-polyethylenimine (PEI) conjugates with entrapped gold nanoparticles in the cavities (RGD-99mTc-Au PENPs) for dual-mode single-photon emission computed tomography (SPECT)/computed tomography (CT) imaging of an orthotopic hepatic carcinoma model. In this study, PEI was successively decorated with diethylenetriaminepentaacetic acid, poly(ethylene glycol) (PEG), and PEGylated RGD segments, and was utilized as an effective nanoplatform to entrap Au NPs and to be labeled with 99mTc. We showed that the designed RGD-99mTc-Au PENPs displayed desirable colloidal stability and radiostability, and cytocompatibility in the investigated concentration range, and could be specifically uptaken by αvβ3 integrin-overexpressing liver cancer cells in vitro. In vivo CT and SPECT imaging results indicated that the particles were able to be accumulated within an orthotopic hepatic carcinoma and displayed both CT and SPECT contrast enhancement in the tumor tissue. With the proven biocompatibility in vivo via histological examinations, the designed RGD-99mTc-Au PENPs may be potentially employed as an effective nanoprobe for a highly efficient dual-mode SPECT/CT imaging of various αvβ3 integrin-overexpressing tumors.

Dual-mode infrared laser-excited synergistic effect in NaGdF4:Er3+ nano-glass ceramics: a kinetic model.

Realization of the absorption and conversion of wide band infrared light have been a challenge in the field of upconversion luminescence. Herein, a facile physical approach is reported to realize the cooperative absorption and conversion of dual-band infrared light by NaGdF4:Er3+ nano-glass ceramics by employing a dual-mode excitation source (980 nm + 1545 nm). A synergistic effect of infrared photons induced by dual-wavelength infrared excitation is observed. The dual-mode excited red emission intensity is 2.76 times the total red emission intensities from 980 nm and 1545 nm single excitation. This upconversion synergistic effect can be modulated by adjusting the single excitation power, and it is proved to originate from ground and excited state absorption, in which the Er3+ ions in metastable states excited by 980 nm (or 1545 nm) photons are excited again by the 1545 nm (or 980 nm) infrared photons. A rate equation model is established to simulate the dynamic process in the dual-mode infrared upconversion process. The synergistic effect provides us with a way to convert two low-energy infrared photons into middle-energy visible photons to enhance the upconversion efficiency of rare earth ion doped glass ceramics.

Sequential Growth of Uniform β-NaYF₄@β-NaLnF₄ (Ln = Y, Lu, Yb) Microcrystals with Luminescent Properties of Multicolor Tuning and Dual-Mode Emission.

We synthesized the uniform core-shell microstructured compounds with hexagonal phase NaYF4:Er/Yb microrods as the core and hexagonal phase NaLnF4 (NaYbF4, NaLuF4:Yb/Tm, NaYF4:Yb/Er, NaYF4:Eu) as the shell based on the hydrothermal reaction. These microscale core-shell structures provided a platform for the spatially confining optical process while possessing high luminescence efficiency. The thickness of the shell could be controlled by adjusting the amounts of shell precursor, which significantly affected the intensity of the shell dopant ions emission and the emission color of core-shell upconversion luminescence (UCL). The uniform NaYF4@NaLnF4 (Ln = Y, Lu, Yb) microrods, with a series of rare-earth ions doped into the core and shell layer at various doping concentrations, achieved color-tuning of the upconversion (UC) emission and dual-mode emission at the single-microcrystal level, thus allowing the efficient utilization of core-shell microcrystals in the photonics and security labeling. This study suggests a new class of luminescent materials in the microscopic field.

An assembly and interaction of upconversion and plasmonic nanoparticles on organometallic nanofibers: enhanced multicolor upconversion, downshifting emission and the plasmonic effect

We present novel inorganic–organic hybrid nanoparticles (HNPs) constituting inorganic NPs, NaY0.78Er0.02Yb0.2F4, and organometallic nanofiber, Tb(ASA)3Phen (TAP). X-ray diffraction, Fourier transform infrared absorption and transmission electron microscopy analyses reveal that prepared ultrafine upconversion NPs (UCNPs (5–8 nm)) are dispersed on the surface of the TAP nanofibers. We observe that the addition of TAP in UCNPs effectively limits the surface quenching to boost the upconversion (UC) intensity and enables tuning of UC emission from the green to the red region by controlling the phonon frequency around the Er3+ ion. On the other hand, TAP is an excellent source of green emission under ultraviolet exposure. Therefore prepared HNPs not only give enhanced and tunable UC but also emit a strong green color in the downshifting (DS) process. To further enhance the dual-mode emission of HNPs, silver NPs (AgNPs) are introduced. The emission intensity of UC as well as DS emission is found to be strongly modulated in the presence of AgNPs. It is found that AgNPs enhance red UC emission. The possible mechanism involved in enhanced emission intensity and color output is investigated in detail. The important optical properties of these nano-hybrid materials provide a great opportunity in the fields of biological imaging, drug delivery and energy devices.

Dual-mode blue emission, paramagnetic properties of Yb3+–Tm3+ co-doped GdOCl difunctional nanostructures

A series of GdOCl:Yb3+, Tm3+ one-dimensional nanostructures with dual-mode [down-conversion (DC) and up-conversion (UC)] luminescence were successfully fabricated by electrospinning technique incorporated with double-crucible chlorination method. The samples have single-phase tetragonal structure with space group of P4/nmm. The diameter and width of GdOCl:10%Yb3+, 0.1%Tm3+ nanofibers and nanobelts are 212.84 ± 1.04 nm and 1.07 ± 0.03 μm, respectively. Excited by 357-nm ultraviolet (UV) light and 980-nm near-infrared (NIR) light, Yb3+ and Tm3+ ions co-doped GdOCl nanostructures exhibit bright blue emission. The mechanism of UC emission is determined to be three-photon process. The energy transfer processes from Yb3+ to Tm3+ are discussed in detail. Moreover, the as-obtained products possess paramagnetic properties at ambient temperature. The type of difunctional one-dimensional nanomaterials has promising applications in anti-counterfeiting, drug delivery, solid state lasers, biolabels and light emitting diodes (LEDs).

Dual-mode blue emission, enhanced up-conversion luminescence and paramagnetic properties of ytterbium and thulium-doped Ba2GdF7 multifunctional nanophosphors

A series of Ba2GdF7:Yb3+, Tm3+ nanophosphors (NPs) with dual-mode (down-conversion (DC) and upconversion (UC)) luminescence were successfully prepared by hydrothermal method at 180°C. The NPs have sphere-like morphology and cubic structure. Under the excitation of ultraviolet 355nm and near-infrared 980nm, Yb3+ and Tm3+ ions co-doped Ba2GdF7 phosphors exhibit bright blue dual-mode emission. The mechanism of UC emissions was determined three-photon absorption. The energy transfer processes from Yb3+ to Tm3+ were discussed in detail. The up-conversion luminescence of Ba2GdF7:Yb3+/Tm3+ nanophosphors were enhanced by introducing the sensitizer Yb3+ ions and modifying the cetyltrimethylammonium bromide (CTAB) surfactant, respectively. Moreover, the as-prepared samples exhibit paramagnetic properties at room temperature. This type of multifunctional nanophosphors have promising applications in anti-counterfeiting, drug delivery, solid state lasers, biolabels, MRI, light emitting diodes (LEDs).

Optically controllable dual-mode switching in single-mode Fabry-Pérot laser diode subject to one side-mode feedback and external single mode injection

In this paper, broadly tunable dual-mode lasing system is presented and demonstrated based on single-mode Fabry-Pérot laser diode subject to the feedback of one side mode amplified by an erbium-doped fiber amplifier in the external feedback cavity. The spacing between two resonance modes in output lasing spectrum is broadly tuned by introducing differently amplified side mode into the single-mode laser via the external cavity consisted of amplifier, filter, and polarization controller so that two difference frequencies of 1THz and 0.6THz are given to display the tunable behavior of dual-mode emission in this work. Therefore, under an external injection mode into the laser condition, the power dependent injection locking and optical bistability of generated dual-mode emission are discussed in detail. At different wavelength detunings, the emitted two resonance modes including the dominant and feedback modes are switched to on- or off-state by selecting proper high-low power level of the external injection mode. As a consequence, the maximum value of achieved dual-mode on-off ratio is as high as up to 45dB.