KZnF3:Cr3+ — A tunable solid state NIR-laser

Pulsed laser operation at room temperature and cw laser output below 260 K has been demonstrated with the laser material KZnF₃:Cr³⁺ in the spectral range between 775—826 nm. The system can be tuned by dispersive elements in the resonator or by temperature variation.     

Efficient Nd:Y<Subscript>0.36</Subscript>Gd<Subscript>0.64</Subscript>VO<Subscript>4</Subscript>-GdCa<Subscript>4</Subscript>O(BO<Subscript>3</Subscript>)<Subscript>3</Subscript> red laser under diode pumping into the emitting level

We report a red laser at 671 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 1342 nm Nd:Y_0.36Gd_0.64VO₄ laser under diode pumping into the emitting level ⁴ F _3/2. An GdCa₄O(BO₃)₃ (GdCOB) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 1.12 W of cw output power at 671 nm is achieved. The optical-to-optical conversion efficiency is up to 6.3%, and the fluctuation of the red output power was better than 3.5% in the given 30 min.     

Saturation spectroscopy of ultraviolet transitions in mercury with a frequency-doubled cw ring dye laser

Doppler-free saturated absorption spectroscopy has been used to study the ultraviolet HgI transitions 6³P₀-6³D₁ at 296.73 nm and 6³P₀-6¹D₂ at 296.76 nm. The required tunable ultraviolet radiation was produced by a ring cavity cw dye laser with intracavity ADA frequency doubler. The isotope shifts of the 6³P⁰ -6³D₁ line for naturally abundant mercury have been measured to within a few MHz.     

Efficient Nd:Y0.5Gd0.5VO4-KTiOPO4 green laser under diode pumping into the emitting level 4F3/2

We report a green laser at 532 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 1064 nm Nd:Y_0.5Gd_0.5VO₄ laser under diode pumping into the emitting level ⁴ F _3/2. A KTiOPO₄ (KTP) crystal, cut for critical type-II phase matching at room temperature is used for second harmonic generation (SHG) of the laser. At an incident pump power of 17.8 W, as high as 4.21 W of cw output power at 532 nm is achieved. The optical-to-optical conversion efficiency is up to 23.6%, and the fluctuation of the green output power was better than 2.8% in the given 30 min.     

Affinement d'une raie de fluorescence de Pr3+: LaAlO3 par excitation laser

A cw dye laser has been used for fluorescence line narrowing experiments by resonant excitation on Pr³⁺ ions in LaAlO₃. Scanning the excitation radiation through the absorption line width corresponding to the transition ³H₄ (0 cm^-1) → ¹D₂ (16 694 cm^-1) while fluorescence was observed, has put into evidence a deformation of the symmetry around Pr³⁺ ions, different for every site.This experiment shows the power of cw dye laser spectroscopy for investigating optical spectra in crystals.     

Stimulated emission and laser action of Pr3+-doped YA1O3

Groundstate absorption, fluorescence, excited-state absorption, and stimulated emission of Pr:YA1O₃ were measured in dependence on the polarization. The results reflect the anisotropy of the host lattice. Especially the polarized spectra of the stimulated emission fit very well with the laser data of this material. Seven cw laser transitions in the visible spectral range obtained so far in Pr:YA1O₃ with argon-ion laser pumping were identified in the spectra of the stimulated emission. In addition, two infrared cw laser transitions were realized. The best results were achieved for the³ P ₀³ F ₄ laser transition at 746.9 nm with a maximum slope efficiency of 24.6%, a maximum output power of 49.6 mW, and a laser threshold of 25 mW.     

Continuous-wave cavity-ringdown detection of stimulated Raman gain spectra

Cavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuous-wave (cw) stimulated Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser light at ∼1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼1064.4 nm. This approach is used to measure cw SRG spectra of the ν ₁ fundamental rovibrational Raman band of methane gas at ∼2916.5 cm⁻¹. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals. Moreover, by employing a ringdown cavity in the form of a ring, the SRG-pump and CRD-detected Stokes beams can co-propagate uni-directionally, which significantly reduces Doppler broadening.     

Local crystallization in an oxyfluoride glass doped with Er3+ ions using a continuous argon laser

Local crystalline formation in erbium doped oxyfluoride glass has been obtained under a cw Argon laser irradiation up to 1.8 W pumping power. By exciting at 514 nm, the emission from 800 nm and 850 nm corresponding to the ⁴S_3/2(²H_11/2)→⁴I_13/2 electronic transitions have been analyzed both inside and outside the irradiated area. The changes in the emission spectra indicate that the high power Ar laser irradiation has resulted in a localized desvitrification process. The temperature dependence of the fluorescence intensity ratio of the 800 nm and 850 nm emission bands has been used to determine the temperature of the irradiated zone. Moreover, the average lifetime of the ⁴S_3/2(²H_11/2) thermalized levels have been measured as a function of the excitation spot position. An important decrease is observed at the irradiated area. These results confirm that a localized cristalline phase has been created by the laser action.     

Tunable single-mode pulsed Ti3+:Sapphire laser injection-seeded by a continuous-wave Cr3+:LiSrAlF6 laser

Spectrally pure high-power tunable single-mode operation of a pulsed Ti³⁺:sapphire laser by a tunable injection-seeding is reported. The injection laser was a cw diode laser pumped, spectrally narrowed tunable Cr³⁺:LiSrAlF₆ (Cr³⁺:LiSAF) laser with a grating in the auxiliary cavity. Single-mode tunable operation of a pulsed Ti³⁺: sapphire ring oscillator was obtained at different wavelengths in the range between 818 nm and 848 nm with a typical linewidth of 0.006 cm^-1. To extend the applicability of this operation to a differential absorption lidar system, the single-mode Ti³⁺:sapphire oscillator output was amplified and a high energy output of 38 mJ was obtained with the same linewidth.     

Continuous-wave Nd:GdVO<Subscript>4</Subscript>/LBO laser at 541.5 nm under diode pumping into the emitting level

We report a green laser at 541.5 nm generation by intracavity frequency doubling of a continuous wave (cw) laser operation of a 1083 nm Nd:GdVO₄ laser under 880 nm diode pumping into the emitting level ⁴ F _3/2. A LiB₃O₅ (LBO) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 17.8 W, as high as 2.52 W of cw output power at 541.5 nm is achieved. The optical-to-optical conversion efficiency is up to 14.2%, and the fluctuation of the green output power was better than 3.6% in the given 30 min.     

Diode-pumped laser and self-frequency-doubling properties of a Nd³⁺:Na₃La₉O₃(BO₃)₈ crystal

We report efficient, diode-pumped, self-frequency doubling (SFD) in the newly developed laser crystal Nd³⁺:Na₃La₉O₃(BO₃)₈ (Nd:NLBO). More than 730?mW of fundamental output power at 1072?nm was achieved with a slope efficiency of 16.2%. With incident pump power of 8?W, 29?mW of green cw laser emission at 536?nm was observed with proper phase matching. This initial performance and the good optical properties of the crystalline host are encouraging for the development of a high power diode-pumped SFD visible light laser source.     

Picosecond Z-scan study of bound electronic Kerr effect in LiNbO3 crystal associated with two-photon absorption

3 crystal have been measured using Z-scan technique with picosecond pulses at 532 nm. The nonlinear absorption coefficient and nonlinear refractive index are determined to be 2.5×10^-10 cm/W and 5.3×10^-15 cm²/W, respectively. Both sign and magnitude of the measured refractive nonlinearity are considerably different from the reported Z-scan results in LiNbO₃ obtained with cw laser beam at 514 nm. The nonlinearities in LiNbO₃ induced by 532 nm picosecond pulses are believed to be mainly due to two-photon absorption and bound electronic Kerr effect associated with the two-photon absorption. Received: 4 July 1996     

CW and tunable laser operation of Yb<Superscript>3+</Superscript> doped CaF<Subscript>2</Subscript>

We present the spectroscopic properties and room temperature of a cw tunable laser operation with Yb³⁺ doped CaF₂ single crystals grown in our laboratory. A laser slope efficiency of 50% with respect to the absorbed 920 nm pump power was obtained, and the laser wavelength could be tuned between 1000 and 1060 nm. PACS 42.55R; 42.70An erratum to this article can be found at     

Diode-pumped Nd:LGS laser emitting at 888 nm

We present what is, to the best of our knowledge, the first diode-pumped Nd:La₃Ga₅SiO₁₄ (Nd:LGS) laser emitting at 888 nm, based on the ⁴ F _3/2-⁴ I _9/2 transition, generally used for a 904 nm emission. The use of a pump module with 16 passes through the crystal allowed the realization of a Nd:LGS thin-disk laser with 1.41 W of continuous wave (cw) output power at 888 nm. Moreover, intracavity second-harmonic generation (SHG) in cw mode has also been demonstrated with a power of 221 mW at 444 nm by using a BiB₃O₆ (BiBO) nonlinear crystal.     

5.3 W deep-blue light generation by intra-cavity frequency doubling of Nd:GdVO4

We report the efficient compacted deep-blue laser at 456 nm generation by intra-cavity frequency doubling of a continuous-wave (cw) laser operation of a diode-pumped Nd:GdVO₄ laser on the ⁴ F _3/2→⁴ I _9/2 transition at 912 nm. The different long LiB₃O₅ (LBO) crystals, cut for critical type I phase matching at room temperature, are used for second harmonic generation (shg) of the laser. At an incident pump power of 30 W, up to 5.3 W of cw output power at 456 nm is achieved with 15-mm-long LBO (3.8 W with 10 mm-long LBO). The conversion efficiency is 17.7% from pump diode input to second harmonic wave output.PACS 42.70.Hj; 42.55.Xi; 42.65.Ky     

Molecular iodine laser optically pumped at 521 nm and 531 nm

We report the observation and identification of over 50 new cw laser lines belonging to the B³∏?X¹∑ system of I₂ optically pumped by a single mode krypton ion laser. When pumping at 531 nm, simultaneous oscillation was achieved on up to 16 lines in the range 540 nm to 650 nm. This system offers considerable potential as a multi-wavelength laser source in interferometry.     

Tunable room-temperature cw laser action in Cr3+: GdScGa-Garnet

We report for the first time on tunable room temperature cw laser action of a transition metal laser material. In Cr³⁺:GdScGa-garnet crystals almost the total fluorescence is channelled into the broad band⁴ T ₂→⁴ A ₂ transition. The fluorescence lifetime is τ=120 μs. Laser pumping in the blue-green and yellow-red spectral range yields pump thresholds around 250 mW and slope efficiencies up to 11%. The wavelength of the free running Cr³⁺ laser is centered at 777 nm.     

Measurement and assignment of new FIR laser lines in12CH3OH and13CH3OH

We have found twelve new FIR laser lines in¹²CH₃OH and thirty three in¹³CH₃OH. Both molecules were pumped by a regular cw CO₂ laser. We have also assigned 20¹³CH₃OH laser lines to specific rotational energy levels in the excited C-O stretchhindered rotation combined states     

Laser-based systems for trace gas detection in life sciences

Infrared gas phase spectroscopy is becoming very common in many life science applications. Here we present three types of trace gas detection systems based on CO₂ laser and continuous wave (cw) optical parametric oscillator (OPO) in combination with photoacoustic spectroscopy and cw quantum cascade laser (QCL) in combination with wavelength modulation spectroscopy. Examples are included to illustrate the suitability of CO₂ laser system to monitor in real time ethylene emission from various dynamic processes in plants and microorganisms as well as from car exhausts. The versatility of an OPO-based detector is demonstrated by simultaneous detection of ¹³C-methane and ¹²C-methane (at 3240 nm) at similar detection limits of 0.1 parts per billion by volume. Recent progress on a QCL-based spectrometer using a continuous wave QCL (output power 25 mW, tuning range of 1891–1908 cm^-1) is presented and a comparison is made to a standard chemiluminescence instrument for analysis of NO in exhaled breath. PACS  42.62 Be; 42.62 Fi     

Spectroscopy,continuous-wave and <Emphasis Type="Italic">Q</Emphasis>-switched diode-pumped laser operation of Er<Superscript>3+</Superscript>,Yb<Superscript>3+</Superscript>:YVO<Subscript>4</Subscript> crystal

We report on the spectroscopy and, for the first time to our knowledge, continuous-wave and Q-switched diode-pumped laser operation of Er,Yb:YVO₄ crystal. Absorption and emission spectra of the crystal were determined. Lifetimes of Er^{3+ 4} I _13/2 and ⁴ I _11/2 levels that define laser performance of the crystal were measured and parameters of energy transfer between Yb³⁺ and Er³⁺ ions were estimated. cw output power of 115 mW with slope efficiency of 5.4% was achieved at 1604 nm. In the Q-switched mode an average output power of 81 mW with slope efficiency of 3.5% and pulse duration of 150 ns was obtained. In quasi-cw regime maximal peak power of 610 mW with slope efficiency of 6.7% was demonstrated. PACS 42.55.Xi; 42.60.Gd; 42.70.Hj