电泳式He-Sr+复合激光特性研究

设计制作了7mm内径和38cm有效激励长度的电泳式He-Sr⁺激光管,采用修饰Blumlein电路,通过纵向高重复率脉冲放电激励,实现了一价锶离子复合激光430.5nm和R-M跃迁激光1.03μm的同时振荡,其中复合激光占主要成分.测量分析了复合激光输出功率与工作参量(脉冲频率,充电电源电压和氦压)的关系曲线.获得了最大激光功率819mW和56mW/cm³功率密度的实验结果. 关键词： 锶离子激光 电泳 脉冲放电     

He–SrCl2 vapor laser excited by Blumlein discharge circuit

An investigation of a He–SrCl₂ vapor laser excited by Blumlein discharge circuit is performed. Dependences of laser output power on the working parameters are obtained by experiment. The optimal operating parameters for lasing on several strontium atom and ion lines are found. The multi-line average output power of 1.32 W and the power specific of 12.46 mW/cm³ are achieved, of which more than 78.1% is concentrated at the 6.45 μm laser line.     

Characteristics of a Cataphoresis He-Ca+ Recombination Laser

A cataphoretic input of calcium vapour into the active volume of pulsed He-Ca^＋ laser is designed and made. The recombination laser at 373.3 nm and the R-M transition laser at 854.6 nm are achieved experimentally with modified Blumlein circuit by high-frequency longitudinal pulsed discharge. The dependences of work parameters such as the pulse frequency, the power supply voltage and the helium pressure on laser output characteristics at 373.3nm line are measured and discussed. The maximum laser output power of 136mW and the specific power of 5.9 m W/cm^3 are obtained, respectively.     

Simultaneous oscillation on UV and IR transitions of the copper ion laser

Simultaneous oscillation of UV (248–270 nm) and IR lines (773–785 nm) in the copper ion laser with helical hollow cathode has been observed using high reflectivity combination mirrors. The output power characteristics of these laser lines are measured as functions of the discharge current and fill-gas pressure. A total laser power of about 100 mW with equal UV and IR contributions was obtained.     

A simple extended cavity diode laser for spectroscopy around 640 nm

We report on an extended cavity diode laser for operation near 640 nm. The laser is continuously tunable in 10 GHz ranges with a maximum output power of 3 mW. The laser system has been constructed using off-the-shelf optoelectronic components and easily machinable mechanical parts. The constructed system has been used to study the saturated absorption of the closed 1s₅–2p₉ neon transition in a radio-frequency discharge that can be maintained at neon pressures down to 10⁻² Pa.     

Xe2Cl fluorescence and absorption in self-sustained discharge XeCl lasers

Fluorescence at 490 nm from the triatomic excimer Xe₂Cl^* has been investigated to determine the 308 nm absorption due to this species in an x-ray preionized, self-sustained gas discharge XeCl laser. The dependence of Xe₂Cl^* density on laser intensity (at 308 nm), buffer gas and Xe and HCl partial pressures has been determined for discharges with a peak electrical power deposition of 2.5 GWl^–1. Xe₂Cl^* absorption is estimated to reach 0.6% cm^–1 under non-lasing conditions but decreases to a non-saturable 0.2% cm^–1 for intracavity laser intensity>1 MW cm^–2. XeCl^* and Xe₂Cl^* fluorescence intensities were found to be a similar for both helium and neon buffer gases but laser output was a factor of two greater with a neon buffer.     

Compact 500.9 nm laser based on doubly resonant intracavity sum–frequency mixing

A compact 500.9 nm laser was realized using doubly resonant intracavity sum–frequency mixing. An Nd:YAG crystal and an Nd:YVO₄ crystal were employed as the gain crystals. In two sub-cavities, 946 nm radiation from the Nd:YAG and 1064 nm radiation from the Nd:YVO₄ were mixed to generate 500.9 nm. In the overlapping of the two cavities, sum–frequency mixing was achieved in a type-II critical phase-matched KTP crystal. An output power of 78 mW at a wavelength of 500.9 nm was generated using a total incident pump power of 4 W and the output light exhibited low noise, with the root-mean-square value being 0.3%.     

Continuous wave and tunable laser operation of Yb3+ in disordered NaLa(MoO4)2

Continuous-wave Yb³⁺ laser operation is studied in single crystals of disordered NaLa(MoO₄)₂ at room temperature. The sample used was grown by the Czochralski technique and incorporates an Yb ion density of 3.1×10²⁰ cm^-3. The effect of the Yb concentration on some of the crystal properties is described as well as the spectroscopic Yb³⁺ properties at 5 K. Maximum slope efficiencies of about 40% for π and 38% for σ polarization were obtained under Ti:sapphire laser pumping near 976 nm, respectively. The maximum output power for the π polarization was 400 mW at 1039.5 nm, the threshold in this case amounted to 240 mW (absorbed pump power). The laser emission was tunable between 1016 and 1064 nm with a Lyot filter. Lasing was also realized by pumping with a fiber-coupled diode laser module. Maximum output power of 900 mW at 1035 nm was achieved in this case for the π polarization and the threshold was 280 mW. The results, in terms of output power and tunability, are superior in comparison to all previous reports on Yb-doped disordered double tungstate or molybdate crystals and represent a significant improvement in comparison to earlier experiments with low-doped Yb:NaLa(MoO₄)₂.PACS 42.55.Rz; 42.55.Xi; 42.70.Hj     

Optimization of the UV CuII laser

The cw output power of the uv CuII laser has been optimized with respect to the hollow cathode geometry, the discharge current, the fill gas pressure and the resonator mirror parameters. A maximum laser output power of 900 mW for multiline operation at 248.6, 259.1, 260.0, and 270.3 nm was achieved with 100 A discharge current, 260 V voltage and 16 mbar fillgas pressure, when a hollow cathode of 1.2 m length and 2×6 mm² cross section was employed. The single-pass pain gl has been estimated to 7%. A hollow cathode cross section of 1.5×4.5 mm² is suggested as an optimum geometry. In addition, some investigations on the mechanism of the laser power decay in Ne–Cu-discharges are presented.     

805-nm diode-pumped continuous-wave 2-µm laser performance of Tm3+:BaGd2(MoO4)4 cleavage plate

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.     

Diode-pumped colour-centre lasers tunable in the 1.5 µm range

Under pumping with a 990 nm, 1 W laser diode, continuous-wave (cw) tunable laser emission in the 1.5 µm wavelength range was obtained from two different colour centres: Tl⁰(1) in NaCl:Tl⁺ and (F ₂ ⁺ )_H in NaCl:OH^–. The results are compared to those recently obtained with a similar apparatus and Tl⁰(1) centres in KCl:Tl⁺. The highest output power (30 mW) and the broadest tuning range (1.48–1.68 µm) were achieved with (F ₂ ⁺ )_H centres.     

Continuous wave laser operation of Yb<Superscript>3+</Superscript>:YVO<Subscript>4</Subscript>

We have demonstrated the continuous wave laser operation of Yb³⁺:YVO₄. For Ti:Al₂O₃ laser pumping at 985 nm, a maximum slope efficiency of 41.1% and a threshold pump power of 76 mW were obtained. The maximum output power was 433 mW at a laser wavelength of 1037 nm.Using a cw diode laser around 974 nm as a pump source, a slope efficiency of 10.9% and a maximum output power of 152 mW were achieved at a laser wavelength of 1039 nm. The laser threshold pump power was 608 mW with respect to the absorbed pump power. The effective emission cross-sections for the ²F_5/2²F_7/2 transition were determined using the Füchtbauer–Ladenburg equation. The maxima of the effective absorption and emission cross-sections were found at 984.5 nm (6.74×10^-20 cm²) in -po larization and 985.5 nm (4.28×10^-20 cm²) also in -p olarization. The upper laser level lifetime was measured with suppression of radiation trapping and is around 318 s. PACS 42.55.Rz; 42.55.Xi; 42.70.Hj     

Cr:YAG laser pumped erbium-doped fibre amplifier with improved power characteristics

An erbium-doped fibre amplifier has been implemented with a 1.48 μm pumping from a Cr⁴⁺:YAG solid state laser. Record launched pump power of 256 mW and output power of 21.8 dBm with this type of pump laser have been obtained. Results are shown for a broad range of pump wavelength (24 nm) and signal wavelength (70 nm).     

Diode-pumped passively Q-switched intracavity frequency doubled Nd:GdVO4/KTP green laser

A compact diode-pumped passively Q-switched intracavity frequency-doubled Nd:GdVO₄/KTP green-pulse laser was demonstrated, using Cr⁴⁺:YAG as a saturable absorber in a simple flat–flat cavity. With a 5.9 W incident pump power, a passively Q-switched green laser was obtained with an average power of 397 mW, repetition rate of 40 kHz, and pulse width of 40 ns, when the initial transmission of Cr⁴⁺:YAG was 85%. The shortest pulse width of 30 ns, the highest green peak power of 696 W and the maximum pulse energy of 21 μJ were obtained when the initial transmission of Cr⁴⁺:YAG was 70%. Under CW green operation, we obtained 440 mW output power.     

Pulsed 469.4 nm hollow cathode He-Kr laser

Design principles, construction and operation characteristics of a pulsed 469.4 nm He-Kr laser are described. The laser was operated in a 20 cm active length transverse hollow cathode discharge and was excited by 50 Hz repetition rate 0.1–1 ms duration square wave current pulses. Cataphoresis of Kr ions was found to play an important role in forming the laser pulse shape. By increasing the voltage a considerable increase of peak laser power occurred, the maximum power obtained was 80 mW. The sealed-off laser was operated using 400 s, 4 A current pulses, pulsed laser power being 20 mW, average power 0.4 mW, respectively. The lifetime of the laser was 440 h, tube failure being due to gas cleanup caused by cathode sputtering.     

An efficient background suppression ratio and output power using a novel fiber loop mirrors technique

This paper demontrates a novel configuration of a linear cavity erbium-doped fiber laser using fiber loop mirrors to effectively suppress the noise generated by the amplified spontaneous emission (ASE). A tunable filter is deployed in each fiber loop mirror to create a narrow passband for the selected mode. The fiber laser produces high background suppression ratio (BSR) of more than 75 dB from 1525 to 1565 nm at the output coupling of 95%. There is no residual ASE detected at the output to verify the effectiveness of the noise filtering in the proposed fiber laser. Low threshold powers are obtained in the range of 2.5–3 mW and the peak power variation is smaller than 1.6 dB.     

224 nm segmented hollow-cathode silver ion laser

The segmented hollow-cathode discharge arrangement is used the first time to excite the 224 nm Ag II laser transition. Quasi-continuous output power of 45 mW is obtained during the 300 s current pulses at optimal discharge conditions (10 hPa of He+4% Ar buffer gas) for discharge current of 3 A. No power saturation is observed up to this current value. An average output power of 0.75 mW is reached using pulse repetition frequency of 190 Hz. The longitudinal mode structure of the TEM₀₀ transversal mode is measured by means of a scanning confocal Fabry–Perot interferometer. Two-mode operation is found to be dominant at high current values. Attempts and suggestions are made to prolong the lifetime of the laser tube. PACS 42.55.Lt; 42.60.Lh; 52.80.-s     

Efficient generation of blue light by intracavity frequency doubling of a cw Nd:YAG laser with LBO

We report on the efficient room-temperature operation of ⁴F_3/2–⁴I_9/2 transition in a diode pumped Nd:YAG laser operating at 946 nm. An output power of 5.1 W and a slope efficiency of 23.6% at 946 nm have been obtained. Different LBO crystals of length 3×3×10 mm³, 3×3×15 mm³, 3×3×18 mm³ were selected as frequency doubling material for comparison. A maximum single-ended output power of 1.3 W at 473 nm was achieved by frequency doubling with an optical conversion efficiency of 5%. When the Nd:YAG rod was replaced by the one with high reflectivity coating at 473 nm on the pump side, the output power of blue light was almost twice that without high reflectivity coating for 473 nm at the same pump power level. Moreover, the theoretical optimum length of LBO crystal for intracavity frequency doubling was discussed, and the experimental results made a good agreement with it.     

LD-pumped passively Q-switched Nd:YVO/LBO red laser with V:YAG

An LD-pumped Nd:YVO₄ passively Q-switched by V:YAG and intracavity frequency doubled by LBO red pulse laser at 671 nm was presented. With 1.6 W incident pump power, average output power of 53 mW, pulse duration (FWHM) of 29.5 ns, pulse repetition rate of 37.2 kHz, peak power of 48.3 W and single-pulse energy of 1.43 μJ were obtained. The stability of pulse energy and repetition rate was better than 3% for 4 h.     

Tunable single-frequency operation of a diode-pumped vertical external-cavity laser at the cesium D<Subscript>2</Subscript> line

We report on a diode-pumped vertical external-cavity surface-emitting laser emitting around 852 nm for Cesium atomic clocks experiments. We have designed a 7-quantum-well semiconductor structure optimized for low laser threshold. An output power of 330 mW was achieved for 1.1 W of incident pump power. Furthermore, a compact setup was built for low-power single-frequency emission. We obtained an output power of 17 mW in a single longitudinal mode, exhibiting both broad (9 nm) and continuous (14 GHz) tunability around the Cesium D₂ line. The laser frequency has been stabilized on an atomic transition with residual frequency fluctuations ∼300 kHz. Through a beatnote experiment the −3 dB laser linewidth has been measured to <500 kHz over 10 ms.