Broadband Optical Amplifiers Research Articles

Broadband tunable optical amplification based on modulation instability characteristic of high-birefringence photonic crystal fibers

A novel high-birefringence photonic crystal fiber (HB-PCF) with two zero-dispersion wavelengths (ZDWs) is designed, and an extraordinarily high modal birefringence of 1.56×10−2 is obtained at pump wavelength λp = 1850 nm. With the designed HB-PCF, the effect of the pump parameters on the modulation instability (MI) in the anomalous dispersion region close to the second ZDWs of the HB-PCF is comprehensively studied in this work. A broadband and tunable optical amplification is achieved by controlling the pump power and the pump wavelength based on the combined operation of Raman effect and cross phase modulation. By optimizing the pump parameters, the amplification bandwidth along the fiber slow axis reaches 152 nm for the pump power Pp = 280 W and the pump wavelength λp=1675 nm, while the gain bandwidth along the fiber fast axis is 165 nm for the pump power Pp = 600 W and the pump wavelength λp = 1818 nm.

Formation, near-infrared luminescence and multi-wavelength optical amplification of PbS quantum dot-embedded silicate glasses

Optical properties of PbS quantum dot (QD)-embedded silicate glasses prepared through post annealing were investigated. By modulating the heat treatment condition, tunable near-infrared (NIR) photoluminescence (PL) was obtained. Noticeable optical amplification was achieved at both 1330nm and 1550nm windows with similar amplification characteristics in single PbS QD-embedded glass, which indicated that broadband optical amplification is expected at the entire PL band of PbS QD-embedded glass. The PbS QD-embedded glass with multi-wavelength optical amplification is promising as the gain medium of broadband fiber amplifiers and tunable fiber lasers.

Effects of Al2O3 composition on the near-infrared emission in Bi-doped and Yb–Bi-codoped silicate glasses for broadband optical amplification

Bi-doped and Yb–Bi-codoped SiO2–Al2O3–CaO glasses were prepared, and the effect of Al2O3 composition on the near-infrared (NIR) emission and energy transfer between Yb3+ and Bin+ (Bi NIR emission centers) were investigated. The introduction of Al2O3 into the glass hosts can vary the NIR luminescence centered at 1300nm and obtain the strongest emission when the concentration of Al2O3 is 15mol%. Efficient energy transfer from Yb3+ to Bin+ is achieved by co-doping of Al2O3. With the increased Al2O3 concentration, the energy transfer efficiency between Yb3+ and Bin+ increased at first and then decreased, maximizing (~79%) at 8mol%. It is suggested that the introduction of appropriate Al2O3 concentration in Yb–Bi-codoped silicate glasses may be an efficient way to realize effective optical amplification with commercially available 976nm LD pumping.

Amplification in Extended Transmission Bands Using Bismuth-Doped Optical Fibers

Bismuth-doped optical glasses emit NIR luminescence in an ultrabroad spectral region of 1000-2000 nm. It makes Bi-doped glasses and glass optical fibers a promising active medium for the creation of Bi-doped fiber lasers and broadband optical amplifiers for this spectral region. Since the first fabrication of Bi-doped fibers in 2005 a large number of papers devoted to the development of Bi-doped fiber lasers and optical amplifiers have been published. It has been shown that Bi-doped fibers are a new breakthrough in active laser materials.

Chalcogenide/tellurite hybrid microstructured optical fiber with high nonlinearity and flattened dispersion

AbstractWe have investigated a new design of hybrid microstructured optical fiber (HMOF) with chalcogenide glass core and tellurite glass cladding. We conducted the chromatic dispersion simulation and nonlinear coefficient calculation by using finite element method. The flattened dispersion with value between ‐20 and 32 ps/nm/km were successfully realized in wide wavelengths ranging from 1.5 to 3.8 μm and the nonlinear coefficient was 86000 km‐1W‐1, one or two orders lager than that of the highly nonlinear fibers reported so far. This HMOF exhibited promising features such as the low flattened dispersion property as well as high nonlinearity, which led to broadband optical amplification, wavelength conversion, and supercontinuum generation from near‐ to mid‐infrared region (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Near-infrared emission from Pr-doped borophosphate glass for broadband telecommunication

Broadband near-infrared emission from Pr-doped borophosphate glass was investigated. The emission band had three peaks centered at ∼1040, 1163, and 1470nm with full widths at half maximum of 108, 147, and 205nm, respectively. These figures cover the entire spectrum of fiber-optic communication bands. The emission lifetimes at 1040, 1163, and 1470nm were 68, 321, and 68μs respectively. The product στ of stimulated emission cross-section (σ) and lifetime (τ) was 3.44×10−23cm2s. These results indicate that the Pr-doped glass can be used as an amplification medium for tunable lasers and broadband optical amplifiers for wavelength division multiplexing transmission system applications.

Spectral properties of and energy transfer in Bi/Tm co-doped silicate glasses

Bi, Tm singly doped and Bi/Tm co-doped glasses with molar compositions of 60SiO2–20Ga2O3–15Na2O–5Al2O3 were prepared by the conventional melt-quenching method. The enhanced emission of the Tm3+:3H4→3F4 transition at 1470 nm, and the quenched emission of the Tm3+:3F4→3H6 transition at 1860 nm were observed for Bi/Tm co-doped silicate glasses under 808 nm excitation. For 980 nm excitation, no Tm-related emission was observed for Tm singly doped glasses, while the emission of the Tm3+:3F4→3H6 transition at 1860 nm was observed for Bi/Tm co-doped glasses. These results indicated that the energy transfer occurred between active Bi ions and Tm3+ in Bi/Tm co-doped silicate glasses, in which the energy corresponding to the Bi-related emission level excited the Tm3+ from 3H6 to the 3H5 level under 980 nm excitation, and from 3F4 to the 3H4 level under 808 nm excitation. The energy-transfer processes were studied on the basis of the Inokuti–Hirayama model, and the energy transfer of the electric dipole–dipole interaction was confirmed to be dominant in Bi/Tm co-doped glasses. The Bi/Tm co-doped silicate glasses may be potential materials for producing broadband optical fiber amplifiers and tunable lasers.

Er3+-doped phosphate glasses with improved gain characteristics for broadband optical amplifiers

Optical properties of Erbium-doped sodium aluminum telluro–phosphate glasses with compositions of 48P2O5–21Na2O–23Al2O3–(8−x)TeO2–(x)Er2O3 (where x=2–7) were investigated. From the measured optical absorption spectra, Judd–Ofelt (JO) analysis has been carried out to predict radiative properties of doped Er3+ ion luminescent levels. The estimated emission cross sections were found to be more than other commonly available short-length optical amplifier (aluminosilicate) glasses. Relative emission intensity enhancement with the increase of Er3+ ion concentration is observed for the laser transition, 4I13/2→4I15/2 (at 1.53μm). Higher emission lifetimes (4.2–6.23ms), higher quantum efficiencies (44–65%) relative at higher Er3+ ion concentrations, high gain bandwidth and gain per unit length at 1.5μm are the most notable features of these glasses for future optical amplifier applications.

Enhanced Luminescent Properties and Mechanism in a Novel Yb–Bi Co-doped Boro-phosphate Glass

A new Yb–Bi co-doped boro-phosphate glass (BP) composition was developed, and strong broadband near‐infrared (NIR) luminescence ranging from 1000 to 1650nm was observed when the sample was excited by 980nm laser. The emission intensity of Yb–Bi:BP glass is about 42 times stronger than that of Bi:BP glass. The full width at half maximum (FWHM) with 174nm, the lifetime (τ) with 961μs and the product of the stimulated emission cross section (σem) and the lifetime, σemτ, with 5.8×10−24 cm2s were obtained which indicates that the glass is a promising candidate for broadband optical fiber amplifiers and tunable lasers. The influence of the introduction of Y2O3 and Al2O3 on the structure of this glass and its excitation mechanism were discussed and analyzed. On the basis of the theoretical analysis of the excitation mechanism, we thought the infrared emission might be attributed to Bi2+ ion in the Yb–Bi co-doped boro-phosphate glass excited by 980nm laser.

Er3+–Yb3+ codoped phosphate glasses used for an efficient 1.5 μm broadband gain medium

In order to develop efficient optical amplifiers with broad and flat gain profiles in the near-infrared range an active phosphate matrix codoped with Er3+ and Yb3+ rare earth optically active ions has been studied by carrying out steady-state and time-resolved luminescence spectroscopies. Taking advantage of the high absorption transition probability of the Yb3+ ions, these ions are excited with cw 980nm radiation from a commercial laser diode and subsequently de-excited by efficiently transferring energy to the Er3+ ions, producing an intense emission at around 1.5μm at which wavelength-division-multiplexing devices work. From the experimental data, the emission cross-section σem(λ) of the 4I13/2→4I15/2 transition at 1.5μm has been calculated using the Füchtbauer–Landerburg method. The result of this calculation, together with the absorption cross-section σabs(λ), allows the gain cross-section G to be estimated. Other important spectroscopic parameters associated with this transition, such as full width at half maximum FWHM, effective bandwidth Δeff and lifetime of the 4I13/2 level τexp, have been measured and analysed as a function of the Er3+ concentration. As figures of merit, FWHM×σem(λ), Δeff×σem(λ) and σem(λ)×τexp calculations have been carried out. Comparing the obtained values to those reported in other Er3+-doped materials, the phosphate glasses doped with 1mol% of Yb2O3 ions and 1–2mol% of Er2O3 can be considered excellent candidates for developing broadband optical amplifiers, providing a large gain cross-section that covers the C (1530–1565nm) and the L (1565–1625nm) bands in the optical telecommunication window.

Infrared broadband emission of bismuth–thulium co-doped lanthanum–aluminum–silica glasses

The Bi–Tm co-doped SiO2–Al2O3–La2O3 (SAL) glasses, which exhibited a broadband near-infrared (NIR) emission was investigated by the optical absorption and photoluminescence spectra. The super broadband near-infrared emission from 1000 to 2100nm, which covered the whole O, E, S, C and L bands, was observed in the Bi–Tm co-doped samples, as a result of the overlap of the Bi-related emission band (centered at 1270nm) and the emission from Tm3+3H4→3F4 transition (1440nm) as well as Tm3+3F4→3H6 transition (1800nm). Relative luminescence intensity at 1270, 1440 and 1800nm wavelength varied depending on the mixing ratio of Bi and Tm and the full-width at half-maximum (FWHM) extending from 1000 to 1600nm could be 400nm. These results indicated that Bi–Tm co-doped SiO2–Al2O3–La2O3 glasses could provide potential applications in tunable lasers as well as the broadband optical amplifiers in WDM system.

Morphology and phase control of fluorides nanocrystals activated by lanthanides with two-model luminescence properties

The morphology, size and phase control of luminescent fluoride nanocrystals through doping has become a new research hotspot due to their improved properties. In this work, Yb(3+) ions, as one of the most efficient sensitizers for various lanthanide activators, were doped in NaGd(Y)F(4) nanocrystals. The results show that no obvious influence was observed for Yb(3+)-doped NaYF(4) nanocrystals, while the influence of Yb(3+) doping on NaGdF(4) nanocrystals was remarkable. The NaGd(1-x)Yb(x)F(4) nanocrystals were synthesized by a hydrothermal route and had a morphology of rice-like nanorods. By controlling the synthesis parameters, the average size and slenderness of the nanocrystals increased gradually with addition of Yb(3+) ions. In contrast, the NaGd(1-x)Yb(x)F(4) nanocrystals maintained a hexagonal phase, which is more beneficial for application as a luminescent host, until the content of Yb(3+) ions reached x = 0.9. The growth and transformation mechanism of NaGd(1-x)Yb(x)F(4) nanocrystals was proposed to be a result of the competition between ion diffusion and an Oswald ripening process. Photoluminescence (PL) spectra confirm the efficient up-conversion and near-infrared (NIR) two-model luminescence properties of Er(3+) (Tm(3+)) activated NaGd(Y)(1-x)Yb(x)F(4) nanocrystals. Simulated analysis results indicate that a colloidal solution of mixed luminescent nanocrystals is expected to find application as the activated medium of three dimensional displays and a broadband optical amplifier.

Tracking Ultrafast Energy Flow in Molecules Using Broadly Tunable Few-Optical-Cycle Pulses

Many (bio) molecules, following light absorption, undergo ultrafast nonradiative decay processes, taking place over timescales of tens to hundreds of femtoseconds. Ultrafast optical spectroscopy allows tracking in real time this energy flow using broadly tunable few-optical-cycle light pulses. Optical parametric amplifiers, thanks to their broad and tunable gain bandwidths, are powerful tools for the generation of such pulses. This paper first reviews our work on broadband optical parametric amplifiers, which led to the demonstration of few-optical-cycle sub-10-fs pulses continuously tunable from the visible (500 nm) to the near-IR (2 μm). We then present selected examples of applications to ultrafast spectroscopy of molecules, such as isomerization of rhodopsin, carotenoid-bacteriochlorophyll energy transfer in light-harvesting complexes, and polymer-fullerene electron transfer in blends for organic photovoltaics.

Nickel-assisted growth and selective doping of spinel-like gallium oxide nanocrystals ingermano-silicate glasses for infrared broadband light emission

The target of taking advantage of the near-infrared light-emission properties of nickelions in crystals for the design of novel broadband optical amplifiers requires theidentification of suitable nanostructured glasses able to embed Ni-doped nanocrystalsand to preserve the workability of a glass. Here we show that Ni doping ofLi2O–Na2O–Ga2O3–GeO2–SiO2 glass (with composition 7.5:2.5:20:35:35 and melting temperature1480 °C, sensibly lower than in Ge-free silicates) enables the selective embedding of nickel ions inthermally grown nanocrystals of spinel-like gallium oxide. The analysis of transmission electronmicroscopy and x-ray diffraction data as a function of Ni-content (from 0.01 to 1 mol%) indicatesthat Ni ions promote the nanophase crystallization without affecting nanoparticle size (∼6 nm) andconcentration (∼4 × 1018 cm − 3). Importantly, as shown by optical absorption spectra, all nickel ions enter into the nanophase, with anumber of ions per nanocrystal that depends on the nanocrystal concentration and ranges from 1 to102. Photoluminescence data indicate that fast non-radiative decay processes become relevantonly at mean ion–ion distances shorter than 1.4 nm, which enables the incorporation of afew Ni ions per nanoparticle without too large a worsening of the light-emission efficiency.Indeed, at 0.1 mol% nickel, the room temperature quantum yield is 9%, with an effectivebandwidth of 320 nm.

Investigation on origin of broadband infrared emission in Bi doped aluminosilicate glasses

Broad infrared emissions at 1131, 1107 and 1291 nm were observed in the bismuth doped aluminosilicate glasses under 532, 690 and 808 nm excitation respectively. The origin of the broadband infrared luminescence was investigated in the aluminosilicate glasses. Based on the energy matching conditions, it is suggested that the infrared luminescence centres might be Bi1+ ions and BiO molecules. The broadband infrared luminescent characteristics of the glasses indicate that they are promising for broadband optical fibre amplifiers and tunable lasers.

Observation of broadband infrared luminescence in a novel Bi-doped P 2O 5–B 2O 3–Al 2O 3 glass

A novel Bi-doped P 2O 5–B 2O 3–Al 2O 3 glass was investigated, and strong broadband NIR (near infrared) luminescence was observed when the sample was excited by 445 nm, 532 nm, 808 nm and 980 nm lasers, respectively. The max FWHM with 312 nm, the lifetime with 580 μs and the σ emτ product with 5.3 × 10 − 24 cm 2 s were obtained which indicates that this glass is a promising material for broadband optical amplifier and tunable laser. The effect of the introduction of B 2O 3 on the glass structure and Bi-ions illuminant mechanism were discussed and analyzed. It is suggested that the introduction of B 2O 3 makes the glass structure closer, and the broadband NIR emission derives from Bi 0: 2D 3/2 → 4S 3/2 and Bi +: 3P 1 → 3P 0 transitions.

High-energy pulse synthesis with sub-cycle waveform control for strong-field physics

Over the last decade, control of atomic-scale electronic motion by non-perturbative optical fields has broken tremendous new ground with the advent of phase-controlled high-energy few-cycle pulse sources1. The development of close to single-cycle, carrier-envelope phase controlled, high-energy optical pulses has already led to isolated attosecond EUV pulse generation2, expanding ultrafast spectroscopy to attosecond resolution1. However, further investigation and control of these physical processes requires sub-cycle waveform shaping, which has not been achievable to date. Here, we present a light source, using coherent wavelength multiplexing, that enables sub-cycle waveform shaping with a two-octave-spanning spectrum and a pulse energy of 15 µJ. It offers full phase control and allows generation of any optical waveform supported by the amplified spectrum. Both energy and bandwidth scale linearly with the number of sub-modules, so the peak power scales quadratically. The demonstrated system is the prototype of a class of novel optical tools for attosecond control of strong-field physics experiments. Researchers present a waveform synthesis scheme that coherently multiplexes the outputs from two broadband optical parametric chirped-pulse amplifiers. The technique provides control at the sub-cycle scale and generates high-energy ultrashort waveforms for use in strong-field physics experiments.

Broadband near-infrared luminescence and tunable optical amplification around 1.55 μm and 1.33 μm of PbS quantum dots in glasses

Silicate glasses containing PbS quantum dots (QDs) with narrow size distribution were prepared through heat treatment. Transmission electron microscopy (TEM) results show that spherical PbS QDs are densely dispersed in the glassy matrix. Using ZnS–PbO to replace PbS as precursor of PbS QDs, the size distribution of PbS QDs in glasses becomes more uniform. Tunable infrared luminescence from 1100 to 2200 nm has been obtained by controlling the glassy matrix and preparation parameters. Obvious optical amplification at communication windows of 1.55 μm and 1.33 μm is probed, and the PbS QDs doped glasses using ZnS–PbO as precursor exhibit larger optical amplification. The PbS QDs doped glasses with intense optical amplification are considered to be promising candidate as gain medium for broadband fiber amplifier and tunable fiber laser.

Erbium‐Doped Fluoroborate Glasses for Near Infrared Broadband Amplifiers

Erbium (Er3+)‐doped alkali lead tellurofluoroborate (RLTB) glasses were prepared and characterized systematically through optical absorption and emission measurements. The emission spectra in the range 450–900 and 1400–1800 nm were recorded by exciting the samples with 532 nm (Nd : YVO4 crystal) and 514.5 nm (Ar+ laser), respectively. Applying Judd–Ofelt analysis, the intensity parameters have been determined using experimental oscillator strengths of absorption bands. From the Judd–Ofelt intensity parameters, some important fluorescence properties such as spontaneous transition probabilities, radiative lifetimes and luminescence branching ratios for the 4S3/2→4I15/2 (0.55 μm), 4S3/2→4I13/2 (0.85 μm), and 4I13/2→4I15/2 (1.54 μm) emission transitions of Er3+ ion in RLTB glasses have been calculated. The continuous pumping of the samples results in fast nonradiative decay through 2H11/2→4F9/2 (~3500 cm−1) transition, which in turn causes the population of Er3+ ions from 2H11/2 state to the higher 4F3/2 state. The emission cross sections determined for the 4I13/2→4I15/2 (1.54 μm) transition using the McCumber theory are in good agreement with the values obtained from the Judd–Ofelt analysis. From evaluated radiative parameters, it is suggested that these RLTB glasses are more suitable candidates for 0.85 and 1.54 μm broadband optical amplifiers.

Fabrication and characterization of Er3+-doped tellurite glass waveguide by Ag+-Na+ ion-exchange method

The planar waveguides of 12Na2O·10NbO2.5·25WO3·53TeO2+1Er2O3 ([NbWEr]) glasses were prepared by Ag+-Na+ ion-exchange at 320-380°C for 5-30 h. The optical properties of the waveguides were characterized. Waveguiding property was successfully confirmed under all the ion-exchange conditions in this study. The thickness of the waveguides increased with increasing ion-exchange temperature and time. The minimum propagation loss of the waveguides was approximately 0.8 dB/cm at 632.8 nm. Hence, the [NbWEr] glass waveguides were considered to be promising for broadband optical amplifiers.