Energy transfer in solid-state dye lasers based on methyl methacrylate co-doped with sulforhodamine B and crystal violet

Laser action in methyl methacrylate （MMA） co-doped with sulforhodamine B and crystal violet dyes was investi- gated. The dye mixture was incorporated into a solid polymeric matrix and was pumped by a 532-nm Nd：YAG laser. Distributed feedback dye laser （DFDL） action was induced in the dye mixture using a prism arrangement both in the donor and acceptor regions by an energy transfer mechanism. Theoretically, the characteristics of acceptor and donor DFDLs, and the dependence of their pulse widths and output powers on acceptor-donor concentrations and pump power, were studied. Experimentally, the output energy of DFDL was measured at the emission peaks of donor and acceptor dyes for different pump powers and different acceptor-donor concentrations. Tuning of the output wavelength was achieved by varying the period of the gain modulation of the laser medium. The laser wavelength showed continuous tunability from 563 nm to 648 nm.

New Progress on All Solid State Laser Technology in China

1 Significance of All Solid State Laser (DPL) Technology in Field of LaserBecause of the advantages of high conversion efficiency, good beam quality, small size and light weight, DPL becomes the hotspot and priority of development of laser technology. It may be the main body of laser in the future and replace gas laser and liquid laser. It is a great revolution of laser technology.The developed countries vie in developing DPL. China has achieved great success in this field, but there is a wide gap between the developed countries and us. We should attach great importance to it.

Infrared Laser Pumped Green and Blue Laser Emissions from a Single Solid State Material Doped by Rare Earth Ions

The possible ways and progress of infrared or red laser pumped green and blue laser emissions from a single solid state material doped by rare earth ions are outlined. The green and blue lasers realized from infrared laser pumped rare earth doped nonlinear laser crystals by means of self frequency conversion and from infrared laser pumped rare earth doped bulk, fiber and microsphere materials by means of frequency upconversion are introduced in detail. Other kinds of devices and methods are also compared. The typical nonlinear laser crystals such as YAl 3(BO 3) 4, GdAl 3(BO 3) 4, YCa 4O(BO 3) 3 , GdCa 4O(BO 3) 3, and the typical upconversion fluoride fibers are compared and analyzed. The major problems remaining to be solved and the developing trends in the area are also discussed.

Modeling the pulse shape of Q-switched lasers to account for terminal-level relaxation

To account for the effect of lower-level relaxation, we have derived a characteristic equation for describing the laser pulse from the modified rate equations for Q-switched lasers. The pulse temporal profile is related to the ratio of the lower-level lifetime to the cavity lifetime and the number of times the population inversion density is above the threshold. By solving the coupled rate equations numerically, the effect of terminal-level lifetime on pulse temporal behaviour is analysed. The mode is applied to the case of a diode-pumped Nd：YAG laser that is passively Q-switched by a Cr4＋ ：YAG absorber. Theoretical results show good agreement with the experiments.

Beam cleanup of a 532-nm pulsed solid-state laser using a bimorph mirror

A successful beam cleanup of a 5-mJ/200-μs pulsed solid-state laser system operating at 532-nm wavelength is demonstrated. In this beam cleanup system, a wave-front sensor-less adaptive optics （AO） system is set up with a 20-element bimorph mirror （BM）, a high-voltage amplifier, a chaxge-coupled device camera, and a control software implementing the stochastic parallel gradient descent （SPGD） algorithm. The brightness of the laser focal spot is improved because the wave-front distortions have been compensated. The performance of this system is presented and the experimental results are analyzed.

All-solid-state doubly resonant sum-frequency continuous-wave laser at 555 nm

A new kind of resonator for doubly resonant continuous-wave （CW） intracavity sum-frequency mixing （SFM） is presented. A coherent radiation of 327 mW at 555 nm is generated by mixing 1342-nm Nd：YVO4 laser and 946-nm Nd：YAG laser. The M^2 beam quality factor of the sum-frequency mixed yellow-green laser is less than 1.7. The low-noise characteristic of the yellow laser is demonitrated.

High power all-solid-state quasi-continuous-wave tunable Ti:sapphire laser system

This paper reports a high power, all-solid-state, quasi-continuous-wave tunable Ti:sapphire laser system pumped by laser diode (LD) pumped frequency-doubled Nd:YAG laser. The maximum tuned output power of 4.2 W (797 nm) and tuned average power of 3.7 W were achieved when fixing the Ti:sapphire broadband output power at 5.0 W and applying 750-850 nm broadband coated mirror.

A narrow-linewidth continuous wave Ho:YALO_3 laser with Fabry–Perot etalons

A narrow linewidth continuous wave Ho：YAP laser with two Fabry-Perot etalons pumped by a Tm：YLF laser is reported. The maximum output power reaches 8.3 W when the incident pump power is 15.8 W, with 52.5% optical-to- optical conversion efficiency and 62.6% slope efficiency. A stable laser output at 2118.1 nm is achieved, with a linewidth less than 0.4 nm （full width at half maximum）. The beam quality factor is M2- 1.25, measured by the traveling knife-edge method.

Laser output of radial-slab solid-state laser

In this letter, numerical simulation and experimental study of a radial-slab solid-state laser are presented. The laser includes four crossing-slabs pumped by four Xe flashlamps. The numerical simulation of coherent intensity in the near field and the far field indicates that the laser with the structure can improve the quality of output beam compared with incoherent beam combination. The radial-slab solid-state laser is fabricated, and initiM experiments are carried out at a pulse repetition of 1 Hz. Nine beams in the near field and one combined beam in the far field are obtained in our initial experiment. The experimental results are consistent with the numerical analysis in the coherent condition. The results show that coherent beam combination is obtained by this laser.

Threshold characteristic of intracavity optical parametric oscillator pumped by all-solid-state Q-switched laser

We derive the threshold pump intensity for a singly resonant intracavity optical parametric oscillator （IOPO） based on a temporal coupled field model. Particular attention is paid to the dependence of the intracavity singly resonant OPO （SRO） threshold intensity on the signal wave output coupling. Meanwhile, a Nd：YAG laser pumped KTiOPO4 （KTP） IOPO for eye-safe laser output is studied experimentally. The experiment is performed with four signal wave output reflectivities of 60%, 70%, 80%, and 90%, respectively. The measured values are in good agreement with the theoretical results. With an output coupler reflectivity of 80%, a peak power of 70 kW at 1572 nm has been obtained at a repetition rate of 3.5 kHz. The pulse width is 4.9 ns. Such investigation is helpful to identifying suitable operational regime of low pump intensity.

Growth and Spectral Characteristics of Yb^(3+)-doped LiGd(MoO_4)_2 Crystal

The Yb3＋-doped LiGd（MoO4）2 crystal with the size up to Φ20×30 mm3 has been grown by Czochralski technique.The polarized room temperature absorption and emission spectra have been investigated.This crystal exhibits a broad absorption band centered at 975 nm with an FWHM of 43 and 59 nm for π-and σ-polarization,respectively,and the corresponding maximal absorption cross-sections are 3.36 and 2.42×10-20 cm2.The emission broadband has an FWHM of 47 and 54 nm for π-and σ-polarization,respectively,with the corresponding emission cross sections of 3.92 and 3.34 × 10-20 cm2 at 1020 nm.The measured fluorescence lifetime is 287 μs.

Growth,Structure,and Spectroscopic Characteristics of the Nd^(3+):LiGd(WO_4)_2 Crystal

The Nd^3＋：LiGd（WO4） 2 crystal with dimensions of 25mm×28mm×16mm was grown by the top-seeded solution growth method from the 60 mol% Li2W2O7 flux. LiGd（WO4） 2 crystallizes in the tetragonal system with space group I41/a（C4h^6） and cell parameters： a = 5.1986 and c = 11.2652A. The hardness is about 5.0 Mohs＇ scale. The specific heat is 0.40 J·g^-1·K^-1 at 50 oC. The thermal expansion coefficients for a-and c-axes are 1.314×10^-5 and 2.052×10^-5 K^-1,respectively. The room-temperature polarized absorption and emission spectra and the fluorescence decay curve was measured. The parameters of oscillator strengths,the spontaneous transition probabilities,the fluorescence branching ratios,the radiative lifetimes,and the emission cross sections have been investigated based on Judd-Ofelt theory and Füchtbauer-Ladenburg method. The absorption cross-section is 5.19×10^-20 cm^2 at 805 nm for π-polarization and its line width is 15 nm; the emission cross section is 1.726×10^-19 cm^2 at 1060.5 nm for π-polarization. The fluorescence and radiative lifetimes are 86 and 158 μs,respectively. The fluorescence quantum efficiency is 54.43%.

Kilowatt-class high-energy frequency conversion to 95 J at 10 Hz at 515 nm

We report on frequency doubling of high-energy,high repetition rate ns pulses from a cryogenically gas cooled multi-slab ytterbium-doped yttrium aluminum garnet laser system,Bivoj/DiPOLE,using a type-I phase matched lithium triborate crystal.We achieved conversion to 515 nm with energy of 95 J at repetition rate of 10 Hz and conversion efficiency of 79%.High conversion efficiency was achieved due to successful depolarization compensation of the fundamental input beam.

Realization of a continuous frequency-tuning Ti:sapphire laser with an intracavity locked etalon

A continuous-wave all-solid-state tunable Ti：sapphire laser with compact configuration is presented. The frequency-tuning range extends from 760 to 825 nm by rotating the birefringent filters. When the intracavity etalon is locked on tile oscillating frequency of the laser and the length of the resonator is scanned by the piezo- electric ceramics transducer, a maximal continuous frequency-tuning range of 15.3 GHz is realized. The obtained Ti：sapphire laser is successfully applied to scan the saturation absorption spectroscopy of D1 transitions of SrRb atoms around the wavelength of 794.97 nm.

Measurement of tropospheric CO_2 and aerosol extinction profiles with Raman lidar

A prototype Raman lidar was designed for monitoring tropospheric CO2 profile and other scientific investigations. The third harmonic of Nd：YAG laser （354.7-nm wavelength） was used as stimulated light source to provide nighttime measurements. Filter with high rejection ratio performance was used to extract CO2 Raman signals from Rayleigh-Mie scattering signals effectively. To improve the real time monitoring function, a two-channel signal collection system was designed to collect CO2 and N2 Raman scattering signals simultaneously. The N2 Raman scattering signals were used to retrieve aerosol extinction coefficient. Typical features of CO2 concentration profile and aerosol extinction coefficient in Hefei were presented. The mixing ratio of atmospheric CO2 in Hefei can reach about 360 - 400 ppmv.

Linearly polarized operation of Yb-doped fiber laser by Brewster's angle-polished fiber end

A new method to obtain linear polarization operation by Brewster＇s angle-polished fiber end is demonstrated. By using the special polarization operation technique together with introducing a narrow-linewidth fiber grating into the laser cavity, a cladding-pumped linear polarization and single-transverse-mode （M2 〈 1.1） Yb-doped fiber laser with narrow linewidth whose full-width at half-maximm （FWHM） is less than 0.2 nm, is obtained in a simple configuration. The output power is up to 10 W which is continuous- wave output at 1085 nm, and the slope efficiency is 63% with respect to the coupled pump power and 75% with respect to the absorbed pump power, respectively. The measured 21-dB polarization extinction ratio does not degrade with the output power. The simplicity of such an approach is highly beneficial for a number of applications, including the use of a fiber laser for the nonlinear wavelength conversion （especially for the intracavity frequency doubling） and for the coherent and spectral beam combination.

Effect of Fe impurity on the optical loss of Nd-doped phosphate laser glass

The optical loss coefficient at 1053-nm wavelength, influenced by Fe ions in N31-type Nd-doped phosphate laser glass, was determined precisely and analyzed in detail. It is found that the optical loss coefficient per unit of Fe concentration （cm^-1/ppmw） increases with Fe concentration in the range of 0--300 ppmw, but it approaches a constant as the Fe concentration is larger than 300 ppmw. Such a concentration effect is due to a shift in the redox equilibrium between Fe^3＋ and Fe^2＋ ions in the glass. The effect of oxygen pressure, temperature, and variable valence states of other metal ions in glass samples on the optical loss is also discussed.

Improving frequency stability of laser by means of temperature-controlled Fabry-Perot cavity

The frequency stability of an all-solid-state Nd:YVO4 laser is significantly improved by means of a specially designed Fabry-Perot (F-P) interferometer used for the frequency standard in the frequency-stabilizing system. The ten.peraturo of the F-P cavity is accurately controlled by a set of thermoelectric cooler (TEC) modules attached on th dy of the cavity and the electronic feedback circuit. We find that the long-term unidirectional frequency shift of the output laser, resulting from the slow increase of the cavity length under the effect of the temperature integration on the cavity body, is essentially eliminated. The frequency stability of the output laser with the power of 530 mW is better than ±200 kHz in 1 minute and ±2.3 MHz iu 40 minutes, respectively. The fluctuation of output power is smaller than ±0.5% over one hour.

Low-threshold mid-IR MgO:PPLN optical parametric generation with high reflectivity mirror for signal wavelength

A low-threshold middle-infrared （mid-IR） MgO：PPLN optical parametric generation （OPG） pumped by a laser diode （LD） end-pumped Z-type Nd：YLF laser at 1047 nm is realized with high reflectivity（HR） mirror for signal. At repetition rate of 10 kHz, the OPG threshold of 50 μJ has been achieved with HR mirror for signal. Compared with the threshold without mirror, the threshold decreases by 17%. Using HR mirror for pump at output side of crystal, the threshold of 40 μJ is achieved. The 2.7 - 4.1 μm continuous tunable output is produced with seven grating periods from 28.5 to 31.5 μm and temperatures from 30 to 200 ℃. When the incident average pump power is 3 W, the OPG idler output power is 0.46 W at 3.26 μm, which corresponds to optical-to-optical conversion efficiency up to 15.3%.

Nonlinear optical properties of polyaniline composite materials

The nonlinear optical properties of polyaniline composite materials （PANI/Au） were studied using the single-beam Z-scan technique. These molecules exhibited a strong reverse saturable absorption and an interesting optical limiting performance with a nanosecond Nd：YAG laser pulses at 532 nm.