Peak Absorption Cross Section Research Articles

Growth, spectroscopy and Dy3+→Tb3+ energy transfer of TbAl3(BO3)4 and Dy3+:TbAl3(BO3)4 crystals

TbAl3(BO3)4 and Dy3+:TbAl3(BO3)4 crystals were grown by the top-seeded solution method and the polarized optical spectra of the crystals were investigated at room temperature. Peak absorption cross-sections for the 6H15/2 → 4I15/2 transition of Dy3+ in the Dy3+:TbAl3(BO3)4 crystal are 1.2 × 10−21 cm2 at 453 nm and 0.6 × 10−21 cm2 at 452.4 nm for σ and π polarizations, respectively. Under excitation at 453 nm, a strong green fluorescence of Tb3+ around 541 nm was observed in the Dy3+:TbAl3(BO3)4 crystal due to the efficient energy transfer from Dy3+ to Tb3+ ions. Peak emission cross-sections for the 5D4→7F5 transition of Tb3+ in the Dy3+:TbAl3(BO3)4 crystal are 2.8 × 10−21 and 1.5 × 10−21 cm2 at 541 nm for σ and π polarizations, respectively. Fluorescence lifetime of the 5D4 level of Tb3+ is 1.4 ms and the efficiency of energy transfer from Dy3+ to Tb3+ ions is about 92% in the Dy3+:TbAl3(BO3)4 crystal. The results show that a commercial high-power 450 nm diode laser may be used as the pumping source for Dy3+/Tb3+ co-doped crystal to realize Tb3+ visible laser.

Polarized spectral characteristics and 1.5–1.6 μm laser operation of Er:Yb:CaSrAl2SiO7 crystal

An Er:Yb:CaSrAl2SiO7 single crystal was grown by the Czochralski method, and its polarized spectral properties were investigated at room temperature. The peak absorption cross-sections of the crystal at 978 nm are 3.30 × 10−20 and 1.42 × 10−20 cm2 for σ and π polarizations, respectively. The peak emission cross-sections at 1536 nm are 0.87 × 10−20 and 0.95 × 10−20 cm2 for σ and π polarizations, respectively. The fluorescence lifetime of the 4I13/2 multiplet of Er3+ is 8.66 ms, and energy transfer efficiency from Yb3+ to Er3+ in the crystal is 70%. Pumped by a 975 nm diode laser, a continuous-wave laser with a slope efficiency of 5.5% and a maximum output power of 70 mW was achieved in the Er:Yb:CaSrAl2SiO7 crystal.

Spectroscopic and 1.5–1.6 μm laser properties of Er:Yb:GdSr3(PO4)3 crystal

An Er:Yb:GdSr3(PO4)3 crystal was grown by the Czochralski method, and its spectroscopic properties were investigated at room temperature. The peak absorption cross section is 1.12 × 10−20 cm2 at 975 nm and the full width at half maximum of the absorption band is 5.8 nm. The peak emission cross section is 0.74 × 10−20 cm2 at 1535 nm and the full width at half maximum of the fluorescence band is 41 nm. Fluorescence lifetime of the 4I13/2 multiplet of Er3+ and Yb3+→Er3+ energy transfer efficiency in the crystal are 7.97 ms and 91.8 %, respectively. End-pumped by a 975 nm diode laser, a 1563 nm continuous-wave laser with a maximum output power of 60 mW and a slope efficiency of 16.1 % was realized in an Er:Yb:GdSr3(PO4)3 crystal at an absorbed pump power of 413 mW. Using a SiO2 birefringent filter as a wavelength tuning element, a continuously tunable 1.5–1.6 μm laser with a range of 45 nm and a maximum output power of 30 mW at 1541 nm was obtained at the same pump power.

Er3+: B2O3-TeO2-ZnO-PbF2−M2O/MF (M = Li, Na, and K) glasses: An inspection of structural, thermal, optical, chromatic, and near-infrared luminescence traits for displays and potential C-band amplification

Six 1.0 mol% Er2O3-doped lead fluoride zinc borotellurite glasses comprising different alkali metal oxides and fluorides (K2O, Na2O, Li2O, KF, NaF, and LiF) have been synthesized via melting and quick-quench approach and structural, thermal, optical, chromatic, upconversion, and NIR (near-infrared) emission features and fluorescence decay times were explored. Main structural units BO3 and BO4, as well as TeO4 and TeO3, are affirmed in all glasses networks by Fourier transform infrared and Raman spectroscopy. For transition 4I13/2 →4I15/2, σemi (emission cross-section) has been assessed by applying Füchtbauer–Ladenburg and McCumber's theories. For Li2O and NaF constituting glasses, acquired peak absorption cross-section (4I15/2→4I13/2) values are 0.999 × 10−20 cm2 and 1.093 × 10−20 cm2, while σemiM (4I13/2→4I15/2) values are 1.064 × 10−20 cm2 and 1.174 × 10−20 cm2 individually. At various P (population inversion) values, calculated gain spectra revealed the C- band amplification from P = 40%.

High-resolution absorption spectroscopy of room-temperature and jet-cooled ammonia between 59,000 and 93,000 cm−1

We present new high-resolution photoabsorption spectra of ammonia spanning the region between 59,000 cm−1 and 93,000 cm−1 that were recorded by using the Fourier Transform Spectrometer at the Synchrotron SOLEIL. This region extends from just above the Franck-Condon envelope for the Ã1A2″ ← X̃1A1′ transition to well above the NH3+X̃+2A2″ ionization threshold. The spectra were recorded at a measured resolution of 0.23 cm−1 in both a room-temperature cell (293 K) and in a slit-jet supersonic expansion (∼70 K). The absolute photoabsorption cross section with an uncertainty of ± 5% is also reported for the room-temperature spectrum. The present resolution is a factor of 10 – 100 times higher than in other recently reported broad band spectra of ammonia, and many of the observed bands show partially resolved rotational structure. We have attempted to assign this structure for a number of these bands. The oscillator strengths extracted from the data are in good agreement with previous measurements but, in the case of structured bands, the present higher resolution measurements return higher peak absorption cross sections, that increase further when the sample is cooled. The present higher resolution spectra suggest that a number of previous vibronic band assignments that were based on quantum defect considerations may require some revision. Finally, we discuss the substantial differences between the photoabsorption and photoionization data just above the first ionization threshold.

Crystal growth and spectral properties of Ho:Sc2O3

Edge-defined film-fed growth (EFG) was successfully used to grow a Ho3+ doped Sc2O3 crystal. At room temperature, the spectroscopic characteristics of the Ho:Sc2O3 crystal were measured. At 650 nm, 1144 nm, and 1922nm, respectively, the peak absorption cross sections were 0.430 × 10−20 cm2, 0.159 × 10−20 cm2, and 0.513 × 10−20 cm2, with complete widths at half maximum of 16 nm, 22 nm, and 122 nm. The crystal's 5I7→5I8 and 5I6→5I7 peak emission cross-sections were 5.205 × 10−21 cm2 and 5.059 × 10−21 cm2, respectively. The measured fluorescence lifetimes 5I6 and 5I7 were 0.135 ms and 8.389 ms, respectively. The results demonstrated the great potential of Ho:Sc2O3 crystal for 3 µm laser operation.

Spectroscopic properties of Er:Yb:Bi4Si3O12 crystal for 1.5–1.6 μm laser

An Er3+ and Yb3+ co-doped Bi4Si3O12 single crystal was grown by the Czochralski method and the spectroscopic properties of the crystal were studied at room temperature in detail. The crystal has a peak absorption cross section of 0.98 × 10−20 cm2 at wavelength of 975 nm, and a peak emission cross section of 1.01 × 10−20 cm2 at wavelength of 1544 nm. The fluorescence lifetimes of the 4I11/2 and 4I13/2 multiplets of Er3+ are 14.4 μs and 5.64 ms, respectively. The fluorescence quantum efficiency of the 4I13/2 multiplet of Er3+ and the Yb3+ → Er3+ energy transfer efficiency are 88.4% and 77.5%, respectively. The results indicate that the Er:Yb:Bi4Si3O12 crystal is a promising 1.5–1.6 μm laser gain medium.

Polarized spectroscopic properties and 1046 nm laser operation of Yb3+:Ca3TaGa3Si2O14 crystal

A Yb3+:Ca3TaGa3Si2O14 single crystal was grown by the Czochralski method. Polarized absorption and fluorescence spectra of the crystal were measured at room temperature. The peak absorption cross sections at 977 nm are 3.69 × 10−20 and 2.03 × 10−20 cm2 for σ and π polarizations, respectively. The crystal has a broad gain band with a full width at half-maximum of 58 nm around 1 μm for σ polarization when the inversion parameter is 0.2. The intrinsic fluorescence lifetime of the 2F5/2 multiplet of the crystal was fitted to be 634 μs. Pumped by a 976 nm diode laser, a 1046 nm continuous-wave laser with a maximum output power of 2.8 W and a slope efficiency of 52.6% was achieved in the crystal. The results show the Yb3+:Ca3TaGa3Si2O14 crystal may be a potential gain medium for tunable and ultrashort pulse lasers at 1 μm.

Crystal growth and optical features study of Dy:Sr3Gd(BO3)3 crystal for yellow laser

The Dy3+:SGB single crystal has been successfully prepared for the first time via the Czochralski technique, of which the optical features were investigated in detail. Based on measured polarized absorption spectra, various spectral parameters were determined via Judd-Ofelt theory. The peak absorption cross-sections at 450 nm for the 6H15/2 → 4I15/2 transition of Dy3+ ions, are 0.66 × 10−21 cm2 for π-polarization and 0.59 × 10−21 cm2 for σ-polarization respectively. The emission cross-sections at 576 nm are 1.91 × 10−21 cm2 and 1.67 × 10−21 cm2 for π and σ polarizations accordingly. Radiative and fluorescence decay times of Dy3+: 4F9/2 level were measured to be 1.607 ms and 1.037 ms, respectively, and the quantum efficiency is 64.5%. All experimental results tell that Dy:SGB could be a potential candidate for direct LD-pumped yellow lasers.

Spectroscopic properties of stoichiometric CaTbAlO4 crystal as a visible laser gain medium

A CaTbAlO4 crystal was grown by the Czochralski method and the polarized spectroscopic properties of the crystal were investigated at room temperature. The peak absorption cross sections at 484.6 nm for σ and π polarizations are 2.97 × 10−22 and 0.68 × 10−22 cm2, respectively. Based on the Judd-Ofelt theory, the spontaneous transition probabilities, fluorescence branching ratios, and radiative lifetime of the 5D4 multiplet of Tb3+ in the crystal were obtained. For σ and π polarizations, the peak emission cross sections at 545 nm are 9.55 × 10−22 and 2.48 × 10−22 cm2, as well as the full widths at half maximum of the green fluorescence bands are about 7 and 10 nm, respectively. The fluorescence lifetime and fluorescence quantum efficiency of the 5D4 multiplet of Tb3+ are 1.84 ms and 79%, respectively. Above results indicate that the CaTbAlO4 crystal is a promising gain medium for visible laser.

Absolute Absorption Cross-Section of the Ã←X˜ Electronic Transition of the Ethyl Peroxy Radical and Rate Constant of Its Cross Reaction with HO2

The absolute absorption cross-section of the ethyl peroxy radical C2H5O2 in the Ã←X˜ electronic transition with the peak wavelength at 7596 cm−1 has been determined by the method of dual wavelengths time resolved continuous wave cavity ring down spectroscopy. C2H5O2 radicals were generated from pulsed 351 nm photolysis of C2H6/Cl2 mixture in presence of 100 Torr O2 at T = 295 K. C2H5O2 radicals were detected on one of the CRDS paths. Two methods have been applied for the determination of the C2H5O2 absorption cross-section: (i) based on Cl-atoms being converted alternatively to either C2H5O2 by adding C2H6 or to hydro peroxy radicals, HO2, by adding CH3OH to the mixture, whereby HO2 was reliably quantified on the second CRDS path in the 2ν1 vibrational overtone at 6638.2 cm−1 (ii) based on the reaction of C2H5O2 with HO2, measured under either excess HO2 or under excess C2H5O2 concentration. Both methods lead to the same peak absorption cross-section for C2H5O2 at 7596 cm−1 of σ = (1.0 ± 0.2) × 10−20 cm2. The rate constant for the cross reaction between of C2H5O2 and HO2 has been measured to be (6.2 ± 1.5) × 10−12 cm3 molecule−1 s−1.

Spectroscopic analysis of Nd:BGSO crystal grown by the micro-pulling-down method

A Nd:BGSO crystal with the dimensions of Φ2 × 131 mm3 has been grown successfully by the micro-pulling-down method. The peak absorption cross-section at 808 nm was calculated to 0.98 × 10−20 cm2 with full-width at half-maximum of 17.4 nm. The stimulated emission cross-section was obtained to be 3.15 × 10−20 cm2 at 1063 nm. The fluorescence and radiative lifetimes of 4F3/2 level were 248 μs and 300 μs respectively. All results indicate that the Nd: BGSO single crystal would be a promising near-IR solid-state laser material.

Crystal growth, spectral properties and Judd-Ofelt analysis of Ho:GdScO3 crystal

Ho3+-doped GdScO3 crystal was successfully grown by the edge-defined film-fed growth (EFG) method. The spectroscopic properties of Ho:GdScO3 crystal were investigated at room temperature. The peak absorption cross-sections were 0.33 × 10−20 cm2 and 1.24 × 10−20 cm2 at 1160 nm and 653 nm with full widths at half maximum of 171.7 nm and 11.5 nm. The peak emission cross-sections of 5I7→5I8 and 5I6→5I7 transitions for the crystal were 0.49 × 10−20 cm2 and 1.24 × 10−20 cm2, respectively. The fluorescence lifetimes of the 5I6 and 5I7 multiplets were measured to be 1.12 ms and 6.13 ms, respectively. The results show that Ho:GdScO3 crystal is a very promising material for 3 μm laser operation.

Polarized spectral properties and laser operation of Nd:SrAl12O19 crystal

Nd:SrAl11O19 (Nd:SRA) crystal has been grown by the Czochralski method. Polarized absorption spectra, polarized fluorescence spectra and fluorescence lifetime were investigated. For σ-polarization, the peak absorption cross section at 798 nm is 2.08 × 10−20 cm2 with full width at half maximum (FWHM) of 10.2 nm and the peak emission cross section is 3.36 × 10−20 cm2 at 1048.5 nm with FWHM of 4.80 nm. The Judd-Ofelt parameters Ω2,4,6 were obtained to be 0.51 × 10−20 cm2, 2.08 × 10−20 cm2, and 2.12 × 10−20 cm2, respectively. Continuous-wave laser operation of the a-cut and c-cut Nd:SRA sample has been demonstrated. The maximum output power of 8.33 W was achieved from c-cut sample at an absorbed power of 27.73 W, corresponding to a slope efficiency of 31.3%.

Crystal growth, structure, optical properties and laser performance of new tungstate Yb:Na2La4(WO4)7 crystals

Abstract The 2 at.% and 10 at.% Yb:Na2La4(WO4)7 crystals with dimensions of O 21 × 24 mm3 and O 24 × 28 mm3 were grown by the Czochralski method. The crystal growth, spectroscopic properties and laser performances of the two crystals were investigated. The peak absorption cross-sections of the 2 at.% and 10 at.% Yb:Na2La4(WO4)7 crystals are 1.51 × 10−20 cm2 and 1.74 × 10−20 cm2 along σ-polarization, as well as 1.61 × 10−20 cm2 and 1.34 × 10−20 cm2 along π- polarization, respectively. The emission cross sections calculated by Fuchtbauer-Ladenburg (FL) method along σ- orientation are 1.45 × 10−20 cm2 and 2.31 × 10−20 cm2 at 1012 nm for the two crystals, respectively. The reciprocity method (RM) was adopted to calculate the emission cross-sections for compassion, and the values at 1012 nm for the two crystals are 0.27 × 10−20 cm2 and 0.34 × 10−20 cm2, respectively. Strong re-absorption effect exists in the crystals, and the analysis of the re-absorption probabilities shows that the crystal with as high as 10 at% Yb3+ concentration has more serious re-absorption effect than many other Yb-doped crystals. The lifetimes of the excited state of Yb3+ in the two crystals were measured and fitted to be 0.392 ms and 0.422 ms, respectively. Based on the absorption and emission spectra, the important laser potential parameters, including the minimum inversion fraction β min , the saturation pump intensity I sat , the minimum pump intensity I min and gain emission cross-sections were evaluated and results indicates that Yb:Na2La4(WO4)7 are candidate lasing mediums. The laser experiments were also performed and continuous-wave (cw) laser actions were demonstrated with the c-cut uncoated crystal samples in a plane-concave cavity, end pumped by a 977 nm laser diode. The maximum output powers are respectively 1.15 W and 0.85 W for the 2 at.% and 10 at.% Yb:Na2La4(WO4)7 crystals, along with the corresponding slope efficiencies of 17.24% and 12.35% when the transmittance of the output coupler is 5%. All the results indicate that the new tungstate Yb:Na2La4(WO4)7 crystal is a good laser medium.

Spectroscopic and continuous-wave laser properties of Er:GdScO3 crystal at 2.7 µm

Er:GdScO3 crystal was grown by the edge-defined film-fed (EFG) method for the first time. The rocking curve showed that the as-grown crystal has a high crystalline quality. The peak absorption cross section at 980 nm is 0.38×10−20 cm2 with full width at half maximum (FWHM) of 19.5 nm and the peak emission cross section at 2720 nm is 0.93×10−20 cm2 with FWHM of 149.0 nm. The fluorescence lifetimes of 4I11/2 and 4I13/2 were fitted to be 2.24 ms and 4.57 ms, respectively. At inversion ratio P≥0.5, the positive local peak of gain cross-section at 2.7 µm was obtained. Continuous-wave laser operation of Er:GdScO3 crystal was demonstrated. The maximum output power of 863 mW was obtained with a slope efficiency of 11.25%. The results indicated that Er:GdScO3 crystal is a potential laser material for 2.7 µm laser.

Growth, thermal, and polarized spectroscopic properties of Nd:CeF3 crystal for dual-wavelength lasers

A Nd:CeF3 crystal was grown successfully by the vertical Bridgman method. The polarized optical properties were investigated for the first time. Based on the Judd–Ofelt theory, the spectral parameters of Nd3+ were studied in detail by using the spectrum of the as-grown crystal. The peak absorption cross-section of σ-polarization at 791 nm is 1.59 × 10−20 cm2, the full width at half maximum (FWHM) is 10 nm. The peak emission cross-section of σ-polarization at 1070 nm is approximately 2.53 × 10−20 cm2, and the three peaks that make up the broadband peak have comparable value. The measured 4F3/2 level fluorescence lifetime is 0.406 ms. Moreover, segregation coefficient of Nd3+, thermal diffusivity coefficient, and thermal conductivity were also measured. We propose that the Nd:CeF3 crystal may be a promising material for 1 μm dual-wavelength laser applications.

Relationship between glass structure and spectroscopic properties in Er3+/Yb3+/Al3+/P5+-doped silica glasses

In this study, Er3+/Yb3+/Al3+/P5+-doped silica (simplified as EYAPS) glasses with different P/Al ratios ranging from zero to infinity were fabricated via the sol-gel method combined with high-temperature sintering. The absorption, emission and fluorescence lifetime of Yb3+ and Er3+ ions as well as the energy transfer efficiency from Yb3+ to Er3+ ions were recorded. The composition-dependent macroscopic properties were correlated to the glass structures, and probed by pulse electron paramagnetic resonance (EPR) and Raman spectroscopy. Results show that the spectral properties of Er3+ and Yb3+ ions and their local environment as well as the global glass network structure of EYAPS glasses are strongly dominated by the P/Al ratio. With the increase of the P/Al ratio, pulse EPR shows that rare earth ions gradually moved from a silicon and aluminum rich environment to a phosphorus rich environment. Raman spectroscopy shows that the maximum phonon energy of EYAPS samples gradually increases from 1200 to 1326 cm−1 due to the formation of AlPO4-like units and P = O double bonds. These structural changes lead to a gradual increase of peak absorption and emission cross sections of Er3+ ions at 1.5 µm, as well as the energy transfer efficiency of 2F5/2 level of Yb3+ to 4I11/2 level of Er3+ ions.

Growth and mid-infrared luminescence property of Ho3+ doped CeF3 single crystal

A Ho3+-doped CeF3 crystal was successfully grown for the first time using the Bridgman method, and its spectral properties were studied. By analyzing the absorption and emission measurements of the Ho:CeF3 crystal with the Judd–Ofelt theory, the intensity parameters Ω2,4,6, emission cross-sections, gain cross-sections, and excited state lifetimes were calculated. It was found that the peak absorption cross-section around 447 nm is 0.4339 × 10−20 cm2, which matched to the commercially available blue laser diode lasers. The 2.0 μm excitation emission of the Ho:CeF3 crystal corresponding to the stimulated emission Ho3+:5I7→5I8 transition has an emission cross section of 0.24 × 10−20 cm2 with FWHM of 146 nm.

CH2OO Criegee intermediate UV absorption cross-sections and kinetics of CH2OO + CH2OO and CH2OO + I as a function of pressure.

The UV absorption cross-sections of the Criegee intermediate CH2OO, and kinetics of the CH2OO self-reaction and the reaction of CH2OO with I are reported as a function of pressure at 298 K. Measurements were made using pulsed laser flash photolysis of CH2I2/O2/N2 gas mixtures coupled with time-resolved broadband UV absorption spectroscopy at pressures between 6 and 300 Torr. Results give a peak absorption cross-section of (1.37 ± 0.29) × 10-17 cm2 at ∼340 nm and a rate coefficient for the CH2OO self-reaction of (8.0 ± 1.1) × 10-11 cm3 s-1, with no significant pressure dependence of the absorption cross-sections or the self-reaction kinetics over the range investigated. The rate coefficient for the reaction between CH2OO and I demonstrates pressure dependence over the range investigated, with a Lindemann fit giving k0 = (4.4 ± 1.0) × 10-29 cm6 s-1 and k∞ = (6.7 ± 0.6) × 10-11 cm3 s-1. The origins of IO in the system have been investigated, the implications of which are discussed.