Broadband Optical Amplifiers Research Articles

Ni(2+) doped glass ceramic fiber fabricated by melt-in-tube method and successive heat treatment.

Glass ceramic fibers containing Ni(2+) doped LiGa(5)O(8) nanocrystals were fabricated by a melt-in-tube method and successive heat treatment. Fiber precursors were prepared by drawing at high temperature where fiber core glass was melted while fiber clad glass was softened. After heat treatment, LiGa(5)O(8) nanocrystals were precipitated in the fiber core. Excited by 980 nm laser, efficient broadband near-infrared emission was observed in the glass ceramic fiber compared to that of precursor fiber. The melt-in-tube method can realize controllable crystallization and is suitable for fabrication of novel glass ceramic fibers. The Ni(2+)-doped glass ceramic fiber is promising for broadband optical amplification.

Optimization for high-energy and high-efficiency broadband optical parametric chirped-pulse amplification in LBO near 800 nm

In this Letter, we present a study of high-energy and high-conversion-efficiency broadband optical parametric chirped-pulse amplification (OPCPA) system with a 100 mm×100 mm×17 mm LBO crystal near 800nm. The results showed that the back-conversion was sensitively affected by the pump intensity and the injected signal intensity. It occurred when the injected signal was above 0.82J with a pump energy of 170J, and this effect also reshaped the amplified spectrum. After optimization, an amplified energy of 45.3J was achieved with a conversion efficiency of 26.3% by the OPCPA. The peak power of the hybrid CPA-OPCPA laser system reached 1.02PW with a compressed duration of 32fs, which is the first reported OPCPA peak power higher than 1PW, to the best of our knowledge.

Spectroscopic and laser properties of Er3+ doped fluoro-phosphate glasses as promising candidates for broadband optical fiber lasers and amplifiers

Different fluoro-phosphate glasses doped with 0.5mol% Er3+ doped are prepared by melt quenching method. Both structural and spectroscopic properties have been characterized in order to evaluate their potential as both laser source and amplifier materials. Optical absorption measurements are carried out and analyzed through Judd–Ofelt and Mc-Cumber theories where spectroscopic parameters such as intensity parameters Ωl (λ=2,4,6), transition probabilities, radiative lifetimes, stimulated absorption cross-sections and emission cross-sections at 1.5μm have been evaluated for Er3+ doped different fluorophosphate glasses. The various luminescence and gain properties are explained from photoluminescence studies. The decay curve analysis have been done for obtaining the decay time constants of Er3+ excited level 4I13/2 in all the fluoro-phosphate glasses. The obtained results of each glass matrix are compared with the equivalent parameters for several other host glasses. These fluoro-phosphate glasses are found to be suitable candidates for laser and amplifier applications.

Enhanced 1.53 µm fluorescence and energy transfer mechanism in tellurite glasses doped with Er3+/Ce3+/Yb3+

Tellurite glasses (TeO2–ZnO–La2O3) doped with Er3+, Er3+/Ce3+ and Er3+/Ce3+/Yb3+ have been prepared using the melt-quenching technique, and the absorption spectra, fluorescence and up-conversion emission spectra together with the differential scanning calorimeter (DSC) curves and X-ray diffraction (XRD) patterns were measured to evaluate the effects of Ce3+ and Yb3+ introduction on the 1.53µm band spectroscopic properties of Er3+, thermal stability and structural nature of glass hosts. The Judd–Ofelt intensity parameters Ωt (t=2,4,6), spontaneous emission probabilities, radiative lifetimes and branching ratios of several Er3+ transitions were calculated from the measured absorption spectra based on the Judd–Ofelt theory. The co-doping with Ce3+ was effective on the suppression of up-conversion emission of Er3+ owing to the phonon-assisted energy transfer: Er3+:4I11/2+Ce3+:2F5/2→Er3+:4I13/2+Ce3+:2F7/2, while the co-doping with Yb3+ had the effect of obviously increasing the Er3+ population at 4I11/2 level via the resonant energy transfer: Yb3+:2F5/2+Er3+:4I15/2→Yb3+:2F7/2+Er3+:4I11/2, both of which contributed the effective enhancement of 1.53µm fluorescence emission. The quantitative studies were carried out to elucidate the energy transfer mechanism by calculating the microscopic parameters and phonon contribution ratios. The glass transition temperature (Tg), crystallization onset temperature (Tx) and the difference ΔT(=Tx−Tg), which characterize the thermal stability of glass host, increased with the Ce3+ and Yb3+ co-doping and for all glass samples the value of ΔT is larger than 145°C. The glass structural nature was demonstrated from the measured XRD patterns with no sharp diffraction peaks. The results of the present work indicated that the prepared Er3+/Ce3+/Yb3+ co-doped tellurite glass is a potential material for developing broad-band and high-gain optical amplifiers and other optical devices.

掺铋光纤的宽带光放大特性研究

掺铋光纤的宽带光放大特性研究

High efficiency, high energy, CEP-stabilized infrared optical parametric amplifier

A high efficiency, tunable, carrier-envelope-phase (CEP) stabilized near-infrared optical parametric amplifier (OPA) is demonstrated with just a single BBO crystal. A white-light continuum produced by a CEP-stabilized laser is seeded into the two stages of the type II OPA system. We achieved a pump-to-signal conversion efficiency of 34% with a single nonlinear crystal. To our knowledge this is the highest conversion efficiency reported in broadband optical parametric amplification, using the two stages. This work demonstrates a compact way to for tunable femtosecond pulses with CEP stabilization.

Enhancement of 1.53 μm emission in erbium/cerium-doped germanosilicate glass pumped by common 808 nm laser diode.

Erbium-doped germanosilicate glasses with various cerium ions contents have been prepared. Optical absorption and 1.53 μm emission spectra were measured to characterize the spectroscopic performances of prepared samples. A detailed study of 1.53 μm spectroscopic properties was carried out when pumped by an 808 nm laser diode. Moreover, an energy level diagram and an energy transfer mechanism between Er3+ and Ce3+ were proposed to elucidate the enhanced 1.53 μm fluorescence. It is found that the prepared samples have optimal spectroscopic properties when the Ce3+ concentration is fixed to 0.5 mol. %. High spontaneous radiative transition probability (172.66 s(-1)), large effective emission bandwidth (74 nm), and emission cross section (9.49×10(-21) cm(2) indicate that 808 nm pumped Er3+/Ce3+ codoped germanosilicate glass might be a suitable material for a broadband optical amplifier.

Performance of megahertz amplified optical time-stretch optical coherence tomography (AOT-OCT).

Enabled by the ultrahigh-speed all-optical wavelength-swept mechanism and broadband optical amplification, amplified optical time-stretch optical coherence tomography (AOT-OCT) has recently been demonstrated as a practical alternative to achieve ultrafast A-scan rate of multi-MHz in OCT. With the aim of identifying the optimal scenarios for MHz operation in AOT-OCT, we here present a theoretical framework to evaluate its performance metric. In particular, the analysis discusses the unique features of AOT-OCT, such as its superior coherence length, and the relationship between the optical gain and the A-scan rate. More importantly, we evaluate the sensitivity of AOT-OCT in the MHz regime under the influence of the amplifier noise. Notably, the model shows that AOT-OCT is particularly promising when operated at the A-scan rate well beyond multi-MHz--not trivially achievable by any existing swept-source OCT platform. A sensitivity beyond 90 dB, close to the shot-noise limit, can be maintained in the range of 2 - 10 MHz with an optical net gain of ~10 dB. Experimental measurement also shows excellent agreement with the theoretical prediction. While distributed fiber Raman amplification is mainly considered in this paper, the theoretical model is generally applicable to any type of amplification schemes. As a result, our analysis serves as a useful tool for further optimization of AOT-OCT system--as a practical alternative to enable MHz OCT operation.

Tailoring chromatic dispersion in chalcogenide–tellurite microstructured optical fiber

We report fabrication of a highly nonlinear hybrid microstructured optical fiber composed of chalcogenide glass core and tellurite glass cladding. The flattened chromatic dispersion can be achieved in such an optical fiber with near zero dispersion wavelength at telecommunication wavelengths λ=1.35–1.7μm, which cannot be achieved in chalcogenide glass optical fibers due to their high refractive index, i.e. n>2.1. We demonstrate a hybrid 4-air hole chalcogenide–tellurite optical fiber (Δn=0.25) with flattened chromatic dispersion around λ=1.55μm. In optimized 12-air hole optical fiber composed of the same glasses, the chromatic dispersion values were achieved between −20 and 32ps/nm/km in a broad wavelength range of 1.5–3.8μm providing the fiber with extremely high nonlinear coefficient 86,000km−1W−1. Hybrid chalcogenide/tellurite fibers pumped with the near infrared lasers give good promise for broadband optical amplification, wavelength conversion, and supercontinuum generation in the near- to mid-infrared region.

Near-IR emission in Pr3+single doped and tunable near-IR emission in Pr3+/Yb3+ codoped tellurite tungstate glasses for broadband optical amplifiers

A study of the broadband near-infrared emission in Pr3+ single doped and Pr3+/Yb3+ codoped tellurite–tungstate glasses for optical amplification is presented. In the Pr3+ single doped samples pumped at 474nm the emission band at 1480nm presents a FWHM of ∼140nm. The Yb3+ addition produces a FWHM broadening up to ∼155nm, achieved through the 1G4–3H5 transition. The emission spectra when the codoped sample is pumped at 980nm shows efficient energy transfer from Yb3+ to Pr3+, resulting in an intense Pr3+ emission around 1330nm. This shows that changing the pump wavelength it is possible to select the 1D2–1G4 or the 1G4–3H5 transition, displacing the emission band from ∼1480 to ∼1330nm.

Optoenergy storage and random walks assisted broadband amplification in Er3+-doped (Pb,La)(Zr,Ti)O3 disordered ceramics

A broadband optical amplification was observed and investigated in Er3+-doped electrostrictive ceramics of lanthanum-modified lead zirconate titanate under a corona atmosphere. The ceramic structure change caused by UV light, electric field, and random walks originated from the diffusive process in intrinsically disordered materials may all contribute to the optical amplification and the associated energy storage. Discussion based on optical energy storage and diffusive equations was given to explain the findings. Those experiments performed made it possible to study random walks and optical amplification in transparent ceramics materials.

Broadband near infrared emission in antimony-germanate glass co-doped with erbium and thulium ions

Antimony-germanate glasses co-doped with Er 3 + / Tm 3 + ions as a material for active waveguides application have been investigated. In result of optimizations of rare earths, concentration wide ( Δλ FWHM = 420 nm ) luminescence emission in the range of 1.4 to 1.9 μm was obtained for molar composition of 1%Er 2 O 3 : 0.25%Tm 2 O 3 . The influence of the molar ratio of active ions on the luminescence spectra has been investigated. Luminescent properties of fabricated glass indicate that elaborated glass is promising material for broad tunable integrated laser sources and broadband optical amplifiers.

宽带光参量放大过程中的转换效率提升

宽带光参量放大过程中的转换效率提升

Er–Yb codoped phosphate glasses with improved gain characteristics for an efficient 1.55 µm broadband optical amplifiers

We have investigated the optical properties of phosphate glasses codoped with Er3+–Yb3+ as a function of Yb3+concentration in order to evaluate their potential as both glass laser systems and amplifier materials. The results of differential scanning calorimetry (DSC) measurements indicate a good thermal stability of phosphate glasses. The Judd–Ofelt (JO) model has been applied to absorption intensities of Er3+ (4f11) transitions to establish the so-called Judd–Ofelt intensity parameters: Ω2, Ω4,Ω6. With the weak spectroscopic quality factors Ω4/Ω6 (0.38), we expect a relatively prominent Infrared laser emission. The intensity parameters are used to determine the spontaneous emission probabilities of some relevant transitions, the branching ratio and the radiative lifetimes of several excited states of Er3+ and compared to the equivalent parameters for other host glasses.Both the IR photoluminescence (PL) intensity and the PL decay time were found to largely increase with Yb3+concentration and the maximum quantum efficiency for the 1.55µm emission was found to be in the order of 91%. We show that the Yb3+ acts as sensitizer for Er3+ and contributes largely to the improvement of the spectroscopic properties of phosphate glasses codoped with Er3+–Yb3+.Using McCumber method, absorption cross-section and calculated emission cross-section, for the 4I13/2→ 4I15/2 transition, were determined and compared for the doped and codoped glasses. The phosphate glasses are promising gain media for developing the solid-state 1.55µm optical amplifiers.

Broadband 1.53 μm emission property in Er3+ doped germa-silicate glass for potential optical amplifier

In this paper, a new type of germa-silicate glass was developed. A detailed investigation of thermal stability, absorption spectrum and 1.53μm emission spectrum was carried out. Based on the absorption spectrum and Judd–Ofelt theory, the Judd–Ofelt parameters and radiative properties were calculated and compared to other glasses. The thermal stability of prepared glass can reach as high as 155°C. Er3+ doped germa-silicate glass possessing high full-width at half-maximum (FWHM) (77nm) and large stimulated emission cross-section (9.55×10−21cm2) shows its potential application in broadband optical amplifier.

Demonstration of optical parametric gain generation in the 1 μm regime based on a photonic crystal fiber pumped by a picosecond mode-locked ytterbium-doped fiber laser

We report the experimental demonstration of the optical parametric gain generation in the 1 μm regime based on a photonic crystal fiber (PCF) with a zero group velocity dispersion (GVD) wavelength of 1062 nm pumped by a homemade tunable picosecond mode-locked ytterbium-doped fiber laser. A broad parametric gain band is obtained by pumping the PCF in the anomalous GVD regime with a relatively low power. Two separated narrow parametric gain bands are observed by pumping the PCF in the normal GVD regime. The peak of the parametric gain profile can be tuned from 927 to 1038 nm and from 1099 to 1228 nm. This widely tunable parametric gain band can be used for a broad band optical parametric amplifier, large span wavelength conversion or a tunable optical parametric oscillator.

Octave-spanning coherent mid-IR generation via adiabatic difference frequency conversion

We demonstrate efficient downconversion of a near-IR broadband optical parametric chirped pulse amplifier (OPCPA) pulse to a 1.1-octave-spanning mid-IR pulse (measured at -10 dB of peak) via a single nonlinearly and adiabatically chirped quasi-phase-matching grating in magnesium oxide doped lithium niobate. We report a spectrum spanning from 2 to 5 μm and obtained by near full photon number conversion of μJ-energy OPCPA pulses spanning 680-870 nm mixed with a narrowband 1047-nm pulse. The conversion process is shown to be robust for various input broadband OPA pulses and suitable for post-amplification conversion for many near-IR systems.

Theoretical studies on optimization of a broadband optical parametric amplifier for enhanced output stability

In this paper, we report theoretical studies on optimization of a broadband optical parametric amplifier (OPA) with enhanced output stability for chirped pulse amplification. Optimization of various signal, pump, crystal and ambient parameters has been carried out to achieve an output energy fluctuation that is much smaller than the pump fluctuation. Different practical examples of single/multi stage OPAs and single/ multi pass OPAs, operating in many optical cycles and few optical cycles regimes have been considered in our studies. It is shown that apart from several crystal and beam parameter parameters, crystal temperature and inter/ intra crystal losses constitute important parameters which can be varied to achieve stable broadband pulse amplification in an optical parametric amplifier.

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.