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Confocal micro-Raman spectroscopy is employed to monitor the damage to haemoglobin from mid-ultraviolet (UVB) radiation. We obtained the Raman spectra of an erythrocyte, which indicated that a peroxidation reaction occurs after UVB radiation. Further, the surface enhanced Raman scattering (SERS) spectra of isolated haemoglobin show that the intensities of the 1375 and 1399 cm bands, which are markers of haem aggregation, obviously increase with prolonged UVB irradiation. This increase reveals that haem aggregation occurs in the peroxidation of erythrocytes. The UV-Vis spectra of isolated haemoglobin indicate that the Soret band, which is indicative of excitonic interactions in the aggregated haems, has a redshift (~12 nm) after 30 min of UVB irradiation of erythrocytes. It can be deduced that an excitonic interaction occurs in the aggregated haems, which is caused by haemoglobin denaturation following UVB irradiation. In addition, the changes of the Raman marker bands during aggregation primarily originate from excitonic interactions. Throughout the process, a higher UVB radiation dose causes greater damage to haemoglobin. [ABSTRACT FROM AUTHOR]

A comparison of two optical frequency standards and a detailed study of the systematic frequency shifts of each Ca single-ion optical frequency standard is presented. The methods used for the systematic shift evaluation of the comparison measurements are also provided. One of the ion traps runs at a chosen operating frequency of 24.7 MHz, determined by the differential scalar polarizability of the clock transition, at which frequency the rf-induced Stark shifts and second-order Doppler shifts cancel each other, yielding a great suppression in the combined micromotion shifts. After compensating for the micromotion, the two optical frequency standards both reach an uncertainty level of a few parts in 10, which is more than an order of magnitude smaller compared to a few years ago. The dominant source of uncertainty is the blackbody radiation shift after minimizing the micromotion-induced shifts. The blackbody radiation shift is evaluated by controlling and measuring the temperature at the trap center. With a measurement over one month, the frequency difference between the two clocks is measured to be 3.2 × 10 with a measurement uncertainty of 5.5 × 10, considering both the statistical (1.9 × 10) and the systematic (5.1 × 10) uncertainties. Due to improvement of the clock laser and better control of the optical and electromagnetic field geometry and the laboratory conditions, a fractional stability of 7 × 10 in 20,000 s of averaging time is achieved. The absolute frequency of the Ca 4 sS-3d D clock transition is measured as 411 042 129 776 401.7 (1.1) Hz, with a fractional uncertainty of 2.7 × 10 using the GPS satellites as a link to the SI second. Details of the method used for the systematic shift evaluation of the measurements are given. [ABSTRACT FROM AUTHOR]

The spatial and temporal behaviors in a diode-end-pumped passively Q-switched laser with a flat-flat resonator are systematically explored as a function of the cavity length. A Nd:YAG/Cr:YAG miniature laser is experimentally used to show that the scale-up of the pulse energy without the higher-order transverse modes can be practically realized by optimizing the cavity length as a function of the pump size. A theoretical analysis is performed to confirm the experimental results. The extracavity second harmonic generation is experimentally conducted to demonstrate the usefulness of the laser design. PACS number(s): 42.60.Gd Q-switching; 42.55.Xi Diode-pumped lasers; 42.55.-f Lasers; 42.65.Sf Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatiotemporal dynamics. [ABSTRACT FROM AUTHOR]

Polarized spectroscopic properties related to 1.07 μm laser operation of a 1.8 at.% Nd:LaBOMoO crystal grown by the Czochralski method were investigated at room temperature. Using a 2.2-mm-thick, Z-cut Nd:LaBOMoO crystal as gain medium, orthogonally polarized dual-wavelength laser at 1,068 and 1,074 nm was first realized in a plano-concave resonator end-pumped by a quasi-continuous-wave 795 nm diode laser. A total output peak power of 1.2 W with slope efficiency of 26 % around 1.07 μm was obtained. The influences of resonator length and pump power on output laser wavelength were also investigated. [ABSTRACT FROM AUTHOR]

The natural birefringence of the Nd:YLF crystal is utilized to achieve a reliable TEM-mode linearly polarized laser at 1053 nm in a compact concave-plano resonator. The efficient selection of the polarization relies on the combined effect of the difference in diffraction angle for σ- and π-polarization of a wedged laser crystal and the alignment sensitivity of an optical resonator. We further employ a Cr:YAG saturable absorber to perform the passively Q-switched operation. At an incident pump power of 12 W, the maximum average output power is up to 2.3 W with a pulse repetition rate of 8 kHz and a pulse width of 9 ns. The pulse energy and peak power are found to be 288 μJ and 32 kW, respectively. [ABSTRACT FROM AUTHOR]

Ce doped ABaPO ( A=Li, Na, K) phosphors were prepared by conventional high temperature solid-state reaction. The phosphors were investigated by XRD, photoluminescence excitation and emission spectra, and luminescence decay curves. The five 5d levels corresponding to the 4f→4f5d transition of Ce ions were identified. The spectroscopic parameters, e.g., the 5d barycenter, the crystal-field splitting, and the Stokes shift, were discussed. LiBaPO:Ce phosphor could be efficiently excited by the near-UV lights (330-420 nm) and showed a broad emission band in the range of 430-620 nm with the maximum wavelength at 468 nm. In contrast, Ce-doped NaBaPO and KBaPO showed only excitation bands in a limited UV region (230-370 nm) and have blue emission at 385 nm and 416 nm, respectively. The temperature quenching of luminescence and the chromaticity coordinates were reported. The luminescence properties were discussed by analyzing the crystal structure and the local surroundings of Ce ions on the Ba sites. [ABSTRACT FROM AUTHOR]

We report a discretely tunable, single and multiwavelength continuous-wave diode-end-pumped laser with a c-cut Nd:YVO crystal lasing on the F-I intermanifold transitions and an intracavity sub-THz free-spectral-range etalon. Experimental results show that it is tunable in the discrete regions of 1066.5-1066.8, 1083.1-1084.6, and 1087.2-1088.2 nm and operates simultaneously at dual-wavelengths of (1084.6, 1087.4), (1066.5, 1088.0), (1066.8, 1083.3) nm by changing the angle of an intracavity etalon with 0.67 THz free-spectral range. With a proper etalon angle, the laser can also simultaneously oscillate at four wavelengths of 1066.9, 1082.9, 1085.7, and 1088.3 nm with a total output power of 1.2 W at an incident diode pump power of 15 W. Similar performance of the laser at different wavelengths was also achieved by using a 0.88 THz free-spectral-range etalon in the same laser cavity. [ABSTRACT FROM AUTHOR]

We report on an efficient high-power passively Q-switched UV laser at 355 nm. We take into account the second threshold criterion and the thermal-lensing effect to design and realize a compact reliable passively Q-switched Nd:YVO laser with Cr:YAG as a saturable absorber. At an incident pump power of 16.3 W, the average output power at 1064 nm reaches 6.2 W with a pulse width of 7 ns and a pulse repetition rate of 56 kHz. Employing the developed passively Q-switched laser to perform the extra-cavity harmonic generations, the maximum average output powers at 532 nm and 355 nm are up to 2.2 W and 1.62 W, respectively. [ABSTRACT FROM AUTHOR]

We present a compact efficient scheme for generation of high-order Laguerre-Gaussian TEM modes in a diode-pumped actively Q-switched Nd:YVO laser. The resonator is composed of two plane mirrors with an intracavity concave lens to expand the cavity mode size for generating a high-power Laguerre-Gaussian TEM mode. We further confirm that the TEM mode is noticeably superior to the TEM mode in the processes of second and third harmonic generations. [ABSTRACT FROM AUTHOR]

We originally demonstrate the use of an AlGaInAs periodic quantum-well absorber to achieve a quasi-continuous-wave (QCW) diode-pumped passively Q-switched Nd:YVO laser with an intracavity optical parametric oscillator (OPO). With a diode-pumping energy of 35 mJ, the output pulse energy and the pulse width at 1573 nm are found to be 1.58 mJ and 26 ns, respectively. The pulse repetition rate can be up to 100 Hz with the overall OPO beam quality M factor to be better than 1.5. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) of LiTb(PO), LiGdSm(PO), and LiTbSm(PO) under vacuum ultraviolet (VUV)/ultraviolet (UV) excitation were studied. We observed the VUV-UV sensitization of Sm emission (561 nm, 601 nm, 649 nm, and 710 nm) by Tb in LiTb(PO):Sm, which leads to the yellow light emission (486 nm, 546 nm, 561 nm, 587 nm, 601 nm, 621 nm, 649 nm, and 710 nm) of LiTb(PO):Sm phosphor under UV and VUV excitation. The emission is a result of partial energy transfer from Tb to Sm, which is discussed in detail in terms of the excitation and emission spectra and decay curves. [ABSTRACT FROM AUTHOR]

Yb:YAl(BO) crystals were grown in LiWO-BO and KMoO-BO fluxes, respectively. In the same experimental conditions, a shorter ultraviolet absorption edge of 278 nm, longer fluorescence lifetime of 1.1 ms, higher slope efficiency of 58%, and lower threshold of 2.4 W were obtained in a Yb:YAl(BO) crystal grown in LiWO-BO flux, whereas the corresponding values for the crystal grown in KMoO-BO traditional flux were 318 nm, 0.7 ms, 46%, and 3.1 W, respectively. Therefore, spectroscopic and laser performances of the one grown in LiWO-BO flux are enhanced due to the improved crystal optical quality. [ABSTRACT FROM AUTHOR]

short-cavity Nd:YVO laser is employed to confirm that a spontaneous mode locking (SML) typically occurs without employing an extra nonlinearity. We further experimentally demonstrate that reducing the number of longitudinal lasing modes can diminish the phase fluctuation and effectively improve the SML pulse stability. Considering the spatial hole-burning (SHB) effect, an analytical expression is derived to accurately estimate the number of longitudinal lasing modes for a practical design guideline. [ABSTRACT FROM AUTHOR]

highly efficient Nd:GdYVO laser by direct in-band pumping at 914 nm is demonstrated for the first time. With an absorbed power of 3.7 W, a maximum output power of 2.65 W at 1064 nm was obtained, corresponding to an optical conversion efficiency of 72%. We also experimentally observed that the laser system could be efficiently operated in the self-mode-locked state in the range of 0.9-3.3 GHz. The pulse width was measured to be 16 ps at a repetition rate of 1.75 GHz. [ABSTRACT FROM AUTHOR]

We present a simple and compact continuous-wave (CW) 1176 nm laser based on self-frequency Raman conversion in continuous-grown YVO/Nd:YVO composite crystal. With a composite crystal 30 mm in length, a maximum output power up to 1.84 W was achieved at the incident diode pump power of 23.6 W. Corresponding to overall optical conversion, the efficiency was 7.8% and the slope efficiency was 8.5%. The conversion efficiency has been doubled compared with the conventional Nd:YVO CW self-frequency Raman laser . The excellent performance of this laser shows that the long continuous-grown YVO/Nd:YVO composite crystal is promising in the application of CW Raman lasers and ideal for miniaturization. [ABSTRACT FROM AUTHOR]

We exploit an AlGaInAs periodic quantum-well absorber with a large modulation strength to realize a multi-mJ passively Q-switched Nd:YVO laser with a repetition rate up to 200 Hz. At a pump energy of 34 mJ, the output pulse energy and the peak power are found to be 3.5 mJ and 1.1 MW, respectively. The fluctuation of the output pulse energy is generally less than ±2%. [ABSTRACT FROM AUTHOR]

We study dispersion of the dielectric function real part ε′ in the terahertz-frequency range for bulk and periodically poled congruent LiNbO and Mg:LiNbO crystals. The concentration of Mg in Mg:LiNbO samples was close to 5 mol%, which is the photorefractive threshold. Approximate expressions for extraordinary polariton dispersion dependence were obtained in the range 0.5-6.5 THz. The influence of Mg-dopant on the optical properties of crystals in the terahertz range is revealed. Changes of the defect structure of lithium niobate crystals are discussed. [ABSTRACT FROM AUTHOR]

Low-voltage cathodoluminescence and vacuum ultraviolet-excited photoluminescence were investigated for Tm-doped phosphor LiGd(PO):0.05Tm and un-doped phosphor LiGd(PO), showing that the photon cascade emission of Gd can be fulfilled upon low-voltage electron beam and 195 nm light excitation, but this process can not be realized at 160 nm excitation. The different spectroscopic feature was discussed in terms of the excitation type and the energy transfer. [ABSTRACT FROM AUTHOR]

End-pumped by a single-stripe 805-nm diode laser, a maximum continuous-wave output power of 290 mW with slope efficiency of 42% and 90 mW with slope efficiency of 44% around 2 µm were achieved in a 1.6-mm-thickness, unprocessed 7.2 at.% Tm3+:BaGd2(MoO4)4 cleavage plate in a hemispherical and plano–plano cavities, respectively, when the absorbed pump power was 830 mW. The dependence of the polarization of output laser on the output coupler transmission was investigated. The influence of upconversion on the laser performance was analyzed. The results show that the unprocessed Tm3+:BaGd2(MoO4)4 cleavage plate is a promising 2-µm laser gain medium pumped by diode laser around 808 nm. [ABSTRACT FROM AUTHOR]

The luminescence properties of polyphosphates NaEu xGd(1− x)(PO3)4 ( x = 0–1.00) and the energy transfer from Gd3+ to Eu3+ were studied. In undoped NaGd(PO3)4 sample, the photon cascade emission of Gd3+ was observed under 8S7/2 → 6GJ excitation (201 nm) in which the emission of a red photon due to 6GJ → 6PJ transition is followed by an ultraviolet photon emission due to 6PJ → 8S7/2 transition. When part of Gd3+ ions in the host NaGd(PO3)4 were substituted by Eu3+ ions, the NaGd(PO3)4:Eu3+ sample showed intensive red emission under 172-nm vacuum-ultraviolet (VUV) excitation which is suitable for mercury-free fluorescent lamps and plasma display panel applications. Based on the VUV–visible spectroscopic characteristics and the luminescence decay properties of NaGd(PO3)4:Eu3+, it was found that the quantum cutting by a two-step energy transfer from Gd3+ to Eu3+ can improve the red emission of Eu3+ ions under VUV excitation but only a part of the excitation energy in the excited 6PJ states within Gd3+ ions can be transferred to Eu3+ ions for its red emission, and the nonradiative energy transfer efficiencies from the excited 6PJ states within Gd3+ to Eu3+ were calculated. [ABSTRACT FROM AUTHOR]

An Er:Yb:Sr3Gd2(BO3)4 crystal was grown by the Czochralski method. The polarized spectral properties of the crystal were investigated, including the polarized absorption and fluorescence spectra and fluorescence decay. The fluorescence quantum efficiency of the upper laser level 4I13/2 of Er3+ ions and the efficiency of the energy transfer from Yb3+ to Er3+ ions were calculated. End-pumped by a diode laser at 970 nm in a hemispherical cavity, a 1.6 W quasi-cw laser at 1.5–1.6 μm with a slope efficiency of 18% and an absorbed pump threshold of 5.9 W was achieved in a 1.8-mm-thick Z-cut Er:Yb:Sr3Gd2(BO3)4 crystal. This crystal has a flat and broad gain curve at 1.5–1.6 μm and so is also a potential gain medium for tunable and short pulse lasers. [ABSTRACT FROM AUTHOR]

A Pr3+:NaGd(MoO4)2 single crystal has been grown by the Czochralski method. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of the crystal were measured at room temperature. The Judd–Ofelt intensity parameters Ω t, q ( t=2,4,6) and the spectroscopic parameters related to the 3 P 0 and 1 D 2 multiplets were obtained and analyzed. The decay mechanisms for the 3 P 0 and 1 D 2 multiplets were also discussed. [ABSTRACT FROM AUTHOR]

A 1.2 mm thick microchip cleaved from a 1.2 at.% Nd3+: BaGd2(MoO4)4 crystal was used as the laser gain medium directly. The laser cavity mirrors were coated on the microchip without cutting and polishing. In the 1.06 μm quasi-CW laser operation, the microchip was pumped by a Ti:sapphire laser with a duty cycle of 10%, the threshold is 10 mW, and the slope efficiency is 50%. In the CW laser operation pumped by a diode laser, the threshold and slope efficiency are 140 mW and 33%, respectively. The results demonstrate that the unprocessed surfaces of the cleaved microchip have good enough flatness and parallelism for laser operation. [ABSTRACT FROM AUTHOR]

We demonstrate a high-peak-power quasi-continuous-wave diode-pumped passive Q-switched Nd:YAG laser at 946 nm. We make a thorough comparison of the output performance between the saturable absorbers of InGaAs quantum wells (QWs) and a Cr4+:YAG crystal. Experimental results reveal that the saturable absorber of InGaAs QWs is superior to the Cr4+:YAG crystal because of the low nonsaturable losses and leads to a pulse energy of 330 μJ with a peak power greater than 11 kW. [ABSTRACT FROM AUTHOR]

The influence of hole shape on extraordinary optical transmission was investigated using hole arrays consisting of rectangular holes with different aspect ratios. It was found that the transmission could be tuned continuously by rotating the hole array. Furthermore, a phase was generated in this process, and linear polarization states could be changed to elliptical polarization states. This phase was correlated with the aspect ratio of the holes. An intuitional model was presented to explain these results. [ABSTRACT FROM AUTHOR]

An Er3+:Bi2(MoO4)3 single crystal has been grown by the Czochralski technique. The Stark sublevels of the 4I15/2 and 4I13/2 multiplets of Er3+ ions in the crystal were determined. The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curve of the crystal were measured at room temperature and the relevant spectroscopic parameters, including the Judd–Ofelt intensity parameters, spontaneous emission probability, fluorescence branching ratio, radiative lifetime, and stimulated emission cross section, were estimated. The effect of re-absorption on the spectroscopic parameters was discussed. When the crystal was excited at 977 nm, up-conversion green fluorescence was observed and discussed. [ABSTRACT FROM AUTHOR]

A Bi2(MoO4)3 single crystal doped with Pr3+ ions has been grown by the Czochralski technique. The polarized absorption and fluorescence spectra as well as the fluorescence decay curve of Pr3+ ions in the crystal were measured at room temperature. The spectroscopic parameters, including the Judd–Ofelt intensity parameters Ωt (t=2, 4, and 6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, stimulated emission cross sections, and fluorescence quantum efficiencies, were calculated. The spectral properties related to laser performance of this crystal were analyzed. The 1 D 2 multiplet of the crystal may be a good upper level for a solid-state laser. [ABSTRACT FROM AUTHOR]

An Er3+/Yb3+-codoped Li6Y(BO3)3 crystal was grown by the Czochralski method. The polarized absorption spectra and the fluorescence decay curve were recorded. The efficiency of energy transfer from Yb3+ to Er3+ ions was estimated. Quasi-continuous-wave output power of 325 mW at 1594 nm was realized under the absorbed pump power of 10.4 W in a hemispherical cavity. The absorbed pump threshold and slope efficiency of the laser are 6.0 W and 7.2%, respectively. [ABSTRACT FROM AUTHOR]

Polarized spectral properties of Er3+:NaGd(WO4)2 single crystal are reported. The crystal was grown by the Czochralski method. The Judd–Ofelt theory was applied to analyze the polarized absorption spectra and then calculate the spontaneous emission probabilities, radiative lifetimes, and branching ratios. Fluorescence decay curves of the 4 I 13/2, 4 I 11/2, and 4 S 3/2 multiplets for the Er3+ ions were measured. Stimulated emission cross-sections of the 4 I 13/2→4 I 15/2 transition obtained by the Fuchtbauer–Ladenberg formula and the reciprocity method were compared. Multi-phonon relaxation rates of the crystal were estimated. Green up-conversion fluorescence around 531 and 552 nm was observed, and the possible up-conversion mechanisms were proposed. [ABSTRACT FROM AUTHOR]

A Pr3+-doped La2(WO4)3 crystal grown by the Czochralski method has been investigated as a promising laser material. The principal axes of the optical indicatrix and Pr3+ concentration of the crystal were determined. The polarized absorption, fluorescence spectra and fluorescence decay curves of the main emission multiplets of the crystal were measured at room temperature. The spectroscopic parameters were obtained by the modified Judd–Ofelt theory combined with the normalized method. The peak stimulated emission cross-sections of the major emission lines were estimated. The good spectroscopic properties imply that the Pr3+:La2(WO4)3 crystal is a potential laser gain medium for solid-state laser and self-stimulated Raman laser applications. [ABSTRACT FROM AUTHOR]

Passively Q-switched laser oscillation at 1060 nm from an unprocessed Nd:LaB3O6 cleavage microchip with a Cr4+:YAG saturable absorber has been demonstrated. The influence of absorbed pump power, output coupler transmission and cavity length on the output pulse characteristics has been investigated. For a plano-concave cavity with a cavity length of 28 mm, pulse with 100 mW average output power, 4.0 μJ energy, 17 ns duration, 25 kHz repetition rate, and 0.24 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 3.5%. For a plano-plano cavity with a cavity length of 5 mm, pulse with 85 mW average output power, 2.1 μJ energy, 2.3 ns duration, 40 kHz repetition rate, and 0.89 kW, peak power was obtained at the absorbed pump power of 1.42 W and output coupler transmission of 5.6%. Because a chopper with a 5% duty cycle was employed in the experiments to reduce the influence of pump-induced thermal loading, the above average output powers were obtained at the 5% duty cycle and extrapolated to 100%. [ABSTRACT FROM AUTHOR]

We report to the best of our knowledge the lowest switching voltage in an electro-optically Q-switched Nd:YVO laser by using a 13-mm long, 14-μm-period PPLN crystal as a Pockels cell. A switching voltage as low as ∼50 V in the PPLN crystal was sufficient to hold off the lasing of the Q-switched laser at a pump power more than two times above its continuous-wave threshold. When the PPLN Q-switch was driven by a 100-V voltage at 6.5 kHz, we obtained 0.9-kW laser peak power from this 1-W diode-pumped Nd:YVO laser system with 13% output coupling. When the PPLN Pockels cell was cascaded with a 5-cm long, 30-μm-period PPLN crystal, we produced ∼μJ/pulse energy at 1.59 μm from optical parametric generation inside the actively Q-switched laser. [ABSTRACT FROM AUTHOR]

The polarized absorption spectra, polarized fluorescence spectra, and fluorescence decay curves of Pr3+ ions in anisotropic PbWO4 single crystal, which was grown by the modified Bridgman method, were measured at room temperature. The standard and modified Judd-Ofelt theories, extended to anisotropic crystal, have been applied to analyze the spectra. The spectroscopic parameters, including the Judd-Ofelt intensity parameters Ot?(t=2,4,6), spontaneous emission probabilities, fluorescence branching ratios, radiative lifetimes, stimulated emission cross sections, and fluorescence quantum efficiencies, were estimated. The good spectroscopic properties show the possible application of the Pr3+-doped PbWO4 crystal as solid-state and self-stimulated Raman laser materials. [ABSTRACT FROM AUTHOR]

Abstract. The nonlinear optical properties of a new polymeric material, the doped film of 4'-(2",4",6"-trichlorophenazoamino)-phenazo-4-nitrobenzene, was studied. Large nonresonant optical nonlinearity (chi[sup (3)] is greater than or equal to 10[sup -28]C[sup 4]m/J[sup 3] or 10[sup -9] esu) and fast response time (t < 20 ps) were measured by forward degenerate four-wave mixing experiment. Optical bistable behavior in a quasi-waveguide interferometer with the thin film of the material was observed. The potential of the material for optical switching was evaluated. [ABSTRACT FROM AUTHOR]

The functioning of a carbon dioxide laser is generalized from the standard low nitrogen concentration, low temperature coolant to the high nitrogen concentration, room temperature air free convection cooling regime. The efficiencies of the two regimes are comparable. Theoretical arguments are presented to support this new regime. [ABSTRACT FROM AUTHOR]

The effect of stimulated Brillouin scattering in remote sensing of the ocean is investigated. It shows that by means of stimulated Brillouin scattering the signal-to-noise ratio of Brillouin lidar can be increased greatly by about 50 times, and its depth resolution can be improved to 1/8 of that with spontaneous Brillouin scattering. [ABSTRACT FROM AUTHOR]

The luminescence properties of polyphosphates NaEu xGd(1− x)(PO3)4 ( x = 0–1.00) and the energy transfer from Gd3+ to Eu3+ were studied. In undoped NaGd(PO3)4 sample, the photon cascade emission of Gd3+ was observed under 8S7/2 → 6GJ excitation (201 nm) in which the emission of a red photon due to 6GJ → 6PJ transition is followed by an ultraviolet photon emission due to 6PJ → 8S7/2 transition. When part of Gd3+ ions in the host NaGd(PO3)4 were substituted by Eu3+ ions, the NaGd(PO3)4:Eu3+ sample showed intensive red emission under 172-nm vacuum-ultraviolet (VUV) excitation which is suitable for mercury-free fluorescent lamps and plasma display panel applications. Based on the VUV–visible spectroscopic characteristics and the luminescence decay properties of NaGd(PO3)4:Eu3+, it was found that the quantum cutting by a two-step energy transfer from Gd3+ to Eu3+ can improve the red emission of Eu3+ ions under VUV excitation but only a part of the excitation energy in the excited 6PJ states within Gd3+ ions can be transferred to Eu3+ ions for its red emission, and the nonradiative energy transfer efficiencies from the excited 6PJ states within Gd3+ to Eu3+ were calculated. [ABSTRACT FROM AUTHOR]