Polarized Absorption Spectra Research Articles

Spectroscopic characteristics and Judd-Ofelt analysis of Pr:GdScO3 crystal

The polarization absorption spectra of Pr3+-doped GdScO3 have been measured. Polarized emission spectra and fluorescence decay from the 3P0 upper level have been investigated. The strongest absorption peaks are located at 448 nm for a, b and c polarization, the absorption cross sections are 1.29 × 10−20 cm2, 0.98 × 10−20 cm2 and 1.57 × 10−20 cm2, respectively. The maximum emission cross section is located at 662 nm, which is 18.55 × 10−20 cm2 (a polarization), 12.74 × 10−20 cm2 (b polarization) and 22.41 × 10−20 cm2 (c polarization), and the FWHM is 10.02 nm, 9.38 nm and 10.14 nm, respectively. The fluorescence lifetime of 3P0 level is 12.39 μs. Those results indicated that Pr3+-doped GdScO3 crystal grown by the Czochralski method is a potential laser medium for visible laser operation.

Growth, spectroscopy and CW laser operation of Ho3+ doped CaY0.9Gd0.1AlO4 single crystal

Ho3+-doped CaY0.9Gd0.1AlO4 single crystal was successfully grown by the Czochralski technique for the first time. The polarized absorption spectra, polarized luminescence spectra and fluorescence decay curve of the crystal were investigated at room temperature. The spectroscopic parameters are calculated based on Judd–Ofelt theory, the values of Ω2,4,6 were calculated to be 3.16 × 10−20 cm2, 3.93 × 10−20 cm2, 0.91 × 10−20 cm2, respectively. The Ho:CaY0.9Gd0.1AlO4 crystal exhibits strong emission at 2013 nm for π- and 2032 nm for σ-polarizations with stimulated emission cross section of 6.64 × 10−20 cm2 and 1.90 × 10−20 cm2, respectively. The fluorescence lifetime of the 5I7 level was measured to be 6.60 ms. The continuous-wave (CW) laser operation of Ho:CaY0.9Gd0.1AlO4 crystal around 2 μm was demonstrated.

Study of the Optical Features of Tb3+:CaYAlO4 and Tb3+/Pr3+:CaYAlO4 Crystals for Visible Laser Applications

Single crystals of Tb3+ single-doped and Tb3+/Pr3+ co-doped CaYAlO4 were produced by the Czochralski method. The room-temperature polarized absorption spectra, emission spectra, and decay curves were recorded and analyzed in detail. The absorption cross-section around 487 nm was found to be 1.53 × 10−22 cm2 for the π polarization in the Tb3+:CaYAlO4 crystal and increased to 5.23 × 10−22 cm2 in the Tb3+/Pr3+:CaYAlO4 crystal. The spectroscopic parameters were calculated through the Judd–Ofelt theory. For the Tb3+:CaYAlO4 crystal, the emission bands of green light at 546 nm and yellow light at 587 nm had fluorescence branching ratios of 64.7% and 6.65% with cross-sections of 8.82 × 10−22 cm2 (σ-polarization) and 0.44 × 10−22 cm2 (π-polarization), respectively. The decay lifetimes of 5D4 multiplets were measured to be 1.41 ms and 1.1 ms for Tb3+:CaYAlO4 and Tb3+/Pr3+:CaYAlO4 crystals, respectively. The energy transfer mechanisms of Tb3+ and Pr3+ and their emission spectral intensities at different temperatures were analyzed. As the temperature increased, the luminescence intensity of the Tb3+:CaYAlO4 and Tb3+/Pr3+:CaYAlO4 crystals decreased almost linearly with the CIE coordinate variation, from (0.370, 0.621) to (0.343, 0.636) and from (0.345, 0.638) to (0.246, 0.698), respectively. The results indicate the potential of Tb3+:CaYAlO4 and Tb3+/Pr3+:CaYAlO4 crystals as visible laser materials with a wide temperature range.

Impact of temperature on optical spectra and up-conversion phenomena in (Lu0.3Gd0.7)2SiO5 crystals single doped with Er3+ and co-doped with Er3+ and Yb3+

Optical absorption and luminescence spectra were recorded at different temperatures for the Czochralski grown crystals of Lu2SiO5-Gd2SiO5 solid solution (LGSO) single doped with Er3+ and double-doped with Er3+ and Yb3+. Optical anisotropy and intensities of Er3+ transitions in LGSO were determined from analysis of room temperature polarized absorption spectra. The crystal field splitting of multiplets and linewidths of Er3+ transitions were derived from low-temperature 6 K absorption and luminescence spectra. Spectra of the Er3+ luminescence excited at 380 nm and of up-converted luminescence excited at 803 nm and 975 nm were recorded for samples with different Yb3+ concentration as a function of temperature between 300 K and 775 K. Thermographic parameters of LGSO:0.5%Er,5%Yb sample derived for FIR (2H11/2/4S3/2) are comparable to those observed in other hosts co-doped with Er and Yb ions, corroborating suitability of this system for the purpose of optical thermometry. For all samples studied the relative thermographic sensitivity Sr(max) values for the 4S3/2/4F9/2, 4F7/2/4S3/2 and 4F7/2/4F9/2 pairs are smaller as compared to 2H11/2/4S3/2 pair but they occur at higher temperatures and therefore may be of interest for specific applications.

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.

The sensitization and deactivation effects of Nd3+ ion in Nd,Ho:CaYAlO4 disordered crystal for 2.86 µm tunable and ultrafast laser

Nd,Ho:CaYAlO4 (Nd,Ho:CYA) crystals with two different Nd3+ doping concentrations for ∼3 µm mid-infrared (MIR) laser were grown successfully by the Czochralski method. The sensitization and deactivation effects of Nd3+ ions were analyzed based on the polarized absorption spectra, mid-infrared and upconversion fluorescence spectra and fluorescence decay curves in detail. Excited by 808 nm laser diode (LD), strong 2.86 µm emission was observed. The maximum emission cross section was calculated to be 1.93 × 10-20 cm2 in 1.0 at.% Nd, 2.5 at.% Ho:CYA, and the FWHM was about 115 nm. The ∼3 µm emission was enhanced by 10 times compared to the 2.5 at.% Nd, 2.5 at.% Ho:CYA crystal. Due to the dual function of Nd3+ as effective sensitizing and deactivating ion, 1.0 at.% Nd, 2.5 at.% Ho:CYA had a relatively longer lifetime 0.240 ms for the upper level 5I6, while the lifetime of the lower level 5I7 reduced to 0.723 ms, which was greatly advantageous to the population inversion. The calculated deactivation efficiency from Ho3+: 5I7 to Nd3+: 4F13/2 was estimated to be 89.66%. All results indicated that 1.0 at.% Nd, 2.5 at.% Ho:CYA crystal is a promising gain medium for ∼3 µm tunable and ultrafast laser output under 808 nm LD pump.

Perovskite-based Lossy-mode resonance sensor in visible light spectrum: Comparison and optimization of optical enhancements

This work considered a two-dimensional hybrid organic–inorganic perovskite thin film with various thicknesses within a sandwiched structure of P3HT: PC61BM and PEDOT: PSS (the top and bottom sides). The optical absorption based on the method of attenuated total reflection was calculated. Then, a detailed primeval study on the lossy mode resonance (LMR) behavior of perovskite thin film as a refractive index sensor was theoretically investigated by defining surrounding media with various refractive indices ranging from 1.33 to 1.44. Since one of the efficient ways to improve the performance of the LMR sensor is optimizing the thickness of the lossy layer, herein, both polarization absorption spectra were studied. The results revealed that the transverse magnetic (TM) mode experienced more loss variation with exhibiting higher red-shift versus rather than transverse electric (TE) mode. The highest sensitivity of 3400 refractive index unit (RIU−1) was achieved; with such high sensitivity to the surrounding environment variations, the proposed structure indicates a versatile prospect. We believe that the perovskite-based LMR sensor can play an influential role in signal detection in biochemical sensors.

Refractive index, thermal, spectroscopic and 1.55 μm laser properties of an Er:Yb:Lu2Si2O7 crystal

Refractive indexes and thermal conductivities at room temperature of an Er:Yb:Lu2Si2O7 crystal were measured to be 1.745, 1.730, 1.695 around 1550 nm and 9.08, 6.98, 7.29 W m−1K−1 along three optical indicatrix X, Y, Z axes, respectively. Room-temperature polarized absorption spectra, fluorescence decay curves and unpolarized up-conversion fluorescence spectrum of the crystal were investigated. Some spectroscopic parameters related to the 1.55 μm laser operation were calculated. End-pumped by a 975 nm laser diode, a 1565 nm continuous-wave laser with maximum output power of 2.18 W and slope efficiency of 21.8% was realized in an Er:Yb:Lu2Si2O7 crystal.

Preparation and systematic spectra analysis of YPO4 crystal co-doped with Er3+ and Yb3+

The Er3+:YPO4 crystals co-doped with different concentrations of Yb3+ (7.5 at.% and 11.5 at.%) were successfully grown by high-temperature solution method with Pb2P2O7 as cosolvent. Crystal growth, structures and spectroscopic characterizations, including polarized absorption spectra, polarized fluorescence spectra and lifetime, were systematically explored and compared. The absorption FWHM at around 975 nm is 17.1 nm for σ-polarizations and 12.0 nm for π-polarizations, which makes Er3+/Yb3+:YPO4 crystal suitable for effective pumping by InGaAs laser diode. Based on J-O theory, the spectroscopic parameters, including J-O intensity, oscillator strength, line strength, fluorescence branching ratios, spontaneous transition rates and radiative lifetime were calculated systematically. Furthermore, four intense emission peaks at around 1505, 1537, 1561 and 1586 nm can be observed in the polarized fluorescence spectra. Theoretically, different frequencies interactions between these wavelengths may be used for the application of generating radiation in the range of 2.9–10.2 THz. The results show that Er3+/Yb3+:YPO4 crystal may be a potential laser material of 1.5–1.6 μm.

Er<sup>3+</sup>,Yb<sup>3+</sup>:YGdSiO<sub>5</sub> Crystal as Gain Media for Lasers Emitting in the Spectral Range of 1.5–1.6 µm

Solid-state erbium lasers, emitting in the spectral range of 1.5–1.6 µm, are of great interest for several industrial applications. Nowadays the Er:glass is the most widespread laser material for obtaining laser radiation at the wavelength near 1.5 µm. However, the maximal output powers of such lasers are restricted by hundreds of milliwatts because low thermal characteristics of the glass host. By this reason the search for new crystalline hosts doped with erbium ions is the actual task.In this article the investigation results of spectroscopic properties of Er3+,Yb3+:YGdSiO5 (YGSO) crystals are reported. Polarized absorption and luminescence spectra were measured. The lifetimes of energy levels were determined. The excited state absorption spectra were measured. It was shown that excited state absorption band does not overlap with gain band in the range 1.5–1.6 µm. The energy transfer efficiency from ytterbium to erbium ions was estimated. The stimulated emission and gain cross-section spectra for Er3+ ions in YGSO were calculated.

Growth, spectroscopic and laser properties of a new Yb0.05:Lu0.03Y0.92PO4 mixed orthophosphate crystal

A new mixed orthophosphate crystal of Yb0.05:Lu0.03Y0.92PO4 was grown by high temperature solution method. The crystal structure, polarization absorption and emission spectra, and fluorescence lifetime were measured and investigated in detail. Continuous-wave (CW) laser action of the mixed crystal was achieved in a simple plane-parallel resonator under diode pumping, producing a maximum CW output power of 0.81 W with a pump power of 2.18 W, the slope and optical-to-optical efficiencies being respectively 46.4% and 39.6%. The wide emission spectrum of the mixed crystal also indicates that it may be of some potential applications in the generation of mode-locked femtosecond pulsed lasers.

Tm,Ho:Ca(Gd,Lu)AlO4 crystals: Crystal growth, structure refinement and Judd-Ofelt analysis

“Mixed” calcium rare-earth aluminate laser host crystals Ca(Gd,Lu)AlO4 (CALGLO) with up to 10.8 at.% Lu codoped with Tm3+ and Ho3+ ions are grown by the Czochralski method along the [001] direction. The segregation of rare-earth ions is studied. The crystal structure is refined by the Rietveld method. Tm,Ho:Ca(Gd,Lu)AlO4 crystallizes in the tetragonal system (sp. gr. I4/mmm) exhibiting a K2NiF4 type structure. The lattice constants are a = 3.6585(6) Å and c = 11.9660(9) Å for a crystal with a composition of CaGd0.8947Lu0.0551Tm0.0448Ho0.0054AlO4. The stability of Ca(Gd,Lu)AlO4 solid-solutions is discussed. The polarized Raman spectra are measured, revealing a most intense mode at 311 cm−1 and a maximum phonon frequency of ∼650 cm−1. The polarized absorption spectra are measured. The transition intensities for the Ho3+ ion are analyzed using the modified Judd-Ofelt theory accounting for configuration interaction.

Nd3+ doped CaLaGa3O7: Growth, structure, and optical properties of a disordered laser crystal

A new disordered crystal of Nd3+-doped CaLaGa3O7 (Nd: CLGO) was successfully grown using the Czochralski method for the first time. The effective segregation coefficient of Nd3+ ions in CLGO was calculated to be 0.68. A systematic investigation of the crystal structure characteristics, fluorescence lifetime, polarized absorption spectra, and emission spectra of Nd: CLGO crystal at room temperature was reported. The maximal absorption cross-sections at 808 nm were 3.18 and 1.34 × 10−20 cm2 for π-polarization and σ-polarization with an FWHM of 16 and 10 nm, respectively, indicating the good pumping efficiency of laser diodes (LDs). The emission cross-sections at 1061 nm of π- and σ-polarization were 7.23 and 6.90 × 10−20 cm2 with an FWHM of 18.8 and 27.8 nm, respectively. Moreover, the measured fluorescence lifetime was 250 μs? Based on the spectral parameters, several important laser parameters were calculated to assess the laser capability. The above results indicate that Nd: CLGO crystal is a promising disordered laser host with AlGaAs LD pumping, and is suitable for generating ultrashort pulse lasers.

Crystal growth, polarization spectral analysis derived from the broadband emission from the 1D2 level of Pr:GdScO3 crystal

Pr3+-doped GdScO3 single crystal was successfully grown by the Czochralski (Cz) method. Polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves were measured at room temperature. The polarized spectroscopic property of Pr:GdScO3 crystal for new-wavelength transition in the near infrared (NIR) region was discussed for the first time. The absorption cross-sections at 600 nm were calculated to be 0.39×10−20 cm2 (E∥a), 0.32×10−20 cm2 (E∥b) and 0.4×10−20 cm2 (E∥c). The emission cross sections at 1053 nm of 1D2 energy level were calculated to be 0.86×10−20 cm2 (E∥a), 0.79×10−20 cm2 (E∥b) and 0.78×10−20 cm2 (E∥c), with FWHM of 57.54 nm, 57.96 nm and 58.96 nm, respectively. The fluorescence lifetime and radiative lifetime of the 1D2 energy levels of Pr3+ ions were 45.46 µs and 393.94 µs, respectively. Those results show that the Pr:GdScO3 crystal should be the potential near infrared laser gain medium originated from the 1D2 transition.

Growth, spectroscopic properties and 1060 nm laser operation of Nd:GdPO4 crystal

A Nd:GdPO4 single crystal with dimensions of 31 × 13 × 10 mm3 was grown by the top-seeded solution method. Polarized absorption and fluorescence spectra of the crystal were measured at room temperature and analyzed based on the Judd-Ofelt theory. The effects of the energy transfer and energy migration processes on the fluorescence lifetime of the 4F3/2 multiplet of Nd3+ were discussed, as well as the concentration-dependent fluorescence quenching effect was also investigated. End-pumped by a quasi-continuous-wave 790 nm laser diode, a 1060 nm laser with a maximum output peak power of 1.12 W and a slope efficiency of 21.9% was obtained in a Nd:GdPO4 crystal at an absorbed pump peak power of 5.39 W.

High Power Diode-Pumped Erbium Laser Emitting at Near 1.5 μm

Solid-state lasers emitting in the 1.5–1.6 μm spectral range are very promising for eye-safe laser range finding, ophthalmology, fiber-optic communication systems, and optical location. The aim of this work is the investigation of spectrosposcopic and laser properties of gain medium based on borate crystal for abovementioned lasers.Spectroscopic and laser properties of Er,Yb:YAl3(BO3)4 crystals with different concentrations of dopants were investigated. Polarized absorption and emission cross-section spectra were determined. The ytterbium- erbium energy transfer efficiency was estimated. The maximal energy transfer efficiency up to 97 % was obtained for Er(4 at.%),Yb(11 at.%):YAl3(BO3)4 crystal.The laser operation of heavily doped crystals with erbium concentration up to 4 аt.% (2.2^1020 cm^3) was realized. By using of Er(2 at.%),Yb(11 at.%):YAl3(BO3)4 crystal a maximal continuous- wave (CW) output power of 1.6 W was obtained at 1522 nm with slope efficiency of 32 %. By using of Er(4 at.%),Yb(11 at.%):YAl3(BO3)4 crystal a maximal peak output power up to 2.2 W with slope efficiency of 40 % was realized in quasi-continuous-wave regime of operation. The spatial profile of the output beam was close to TEM00 mode with M2 < 1.2 during all laser experiments.Based on the obtained results, it can be concluded that Er,Yb:YAl3(BO3)4 crystals are promising active media for lasers emitting in the spectral range of 1.5-1.6 pm for the usage in laser rangefinder and laser- induced breakdown spectroscopy systems, and LIDARs.

Electronic spectra and structure of 1- and 2-fluoronaphthalene impurity centers in crystalline naphthalene

The results of experimental investigations on the low-temperature fluorescence and absorption spectra of the 1- and 2-fluoronaphthalene impurities in the crystalline naphthalene are presented and analyzed. When the 1- and 2-fluoronaphthalene concentrations are less than 1%, the absorption and fluorescence spectra are shown to be composed of two identical band series, induced by the formation of two different centers, consisting of the single impurity molecules. The impurity concentration increase of over 1% results in the appearance of the additional structure in the polarized absorption spectra near the 0-0 bands of the single centers in a form of narrow bands with similar intensity and different polarization. This structure is associated with a formation of impurity paired centers, consisting of the two resonantly interacting molecules of either 1-fluoronaphthalene, or 2-fluoronaphthalene. Besides, in the case of the 2-fluoronaphthalene, the absorption spectra contain intense peaks, located ∼ 45 cm−1 higher in frequency, relative to the 0−0 transition bands for each single-center, and consisted of complexes of narrow lines. These spectral peaks are also explained by a formation of impurity paired centers, but here interactions between the molecules are not resonant. For the pure naphthalene crystal factors, causing the observation of additional oppositely polarized weak bands in the absorption spectra at ∼ 10 cm−1 near the Davydov doublet components, are described.

Growth and spectroscopic analyses of Yb,Ho:CaYAlO4 disordered crystal for ~3 μm mid-infrared laser

Ho:CaYAlO4 (Ho:CYA) and Yb,Ho:CaYAlO4 (Yb,Ho:CYA) disordered crystals exhibiting high optical nature were successfully grown by the Czochralski method for ~3 μm mid-infrared laser. The polarized absorption spectra and J-O parameters were analyzed. A strong 2.86 μm emission with the FWHM of 111 nm had been realized in Yb,Ho:CYA crystal via Yb3+ ions sensitization, corresponding to the emission cross-section of 1.4 × 10−20 cm2. The comparable emission peak at 1.2 μm and fluorescence lifetime of Ho3+:5I6 level indicated an effectively energy transfer from Yb3+:2F5/2 to Ho3+:5I6. The efficiency was calculated to be about 83.5%. All above results suggest that Yb,Ho:CYA crystal is a potential laser host for ~3 μm mid-infrared ultrafast and tunable laser under the commercial 980 nm LD pump.

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%.