Observation of 280 nm and 298 nm ultraviolet emissions in sodium vapor

Dye laser output around 578 nm is utilized to pump sodium vapor confined in a heatpipe. Fixed wavelength ultraviolet emissions at 280 nm and 298 nm are observed for the first time and can be explained by anti-Stokes Raman scattering and two photon emission respectively. In addition, there are tunable emission lines around 280 nm and 298 nm, the frequencies of which vary with pump laser wavelength. These tunable lines can be explained by four-wave mixing schemes.     

High-power dye laser in the near infrared

A tunable wavelength, laser beam of very high spectral luminance in the near infrared is obtained by amplification of a monochromatic laser line emitted by a tunable dye oscillator. Optical pumping of the oscillator and the four-stage amplifier is effected by a giant pulse ruby laser. The energy obtained with a solution of 3,3′ dimethyl 2,2′ oxatricarbocyanine iodide (D.O.T.C.) in dimethyl sulfoxyde is 1 J at 7699 Å. The laser pulse of spectral width Δλ = 0.065 Å is emitted at a rate of 0.1 Hz. The half-peak pulse duration is 15 ns.     

Studies of tunable four-photon parametric fluorescence of crystals in the visible region

Tunable four-photon parametric fluorescence, which is valuable for investigating material nonlinearities and parametric devices, was studied theoretically and experimentally.Theoretical analysis leads to the conclusion that the emitted power depends directly on the focusing of the pumping beam, unlike the process of three-photon parametric fluorescence which is independent of the focusing of the pumping beam. The calculation of the phasematching conditions for nonlinear crystals such as KDP, ADP, TiO₂ and CdS shows that collinear phase-matching can be realised over the visible region using a ruby laser for pumping. Experimentally, tunable emission was observed in the visible range from 4200 Å to 5300 Å with KDP and ADP crystals pumped by a Q-switched ruby laser.     

Generation of tunable coherent VUV radiation by anti-Stokes Raman scattering of excimer-pumped dye laser radiation

A straightforward method of generating tunable coherent VUV radiation is described. Radiation down to 1362 Å was produced by Raman shifting the output of a commercially produced, excimer-pumped dye laser system. It is shown that generation of VUV radiation at 1640 Å is more efficient using the 8th anti-Stokes line from a UV dye than by using the 10th anti-Stokes line from a visible dye which had twice the output power.     

Continuously tunable VUV radiation (129–210 nm) by anti-Stokes Raman scattering in cooled H2

The generation of tunable vacuum ultraviolet radiation by anti-Stokes Raman scattering of tunable ultraviolet dye-laser radiation in cold hydrogen has been investigated. The scattering efficiency of XeCl laser and Nd:YAG laser pumped commercial dye lasers and the influence of different beam profiles has been studied. Up to 12 anti-Stokes orders down to 129 nm were observed with output powers between about 20 kW at =191 nm and somewhat less than 100 W at =129 nm. The efficiency of transversely pumped lasers with an intensity peaked in the center of the beam profile was found to be higher than doughnut shaped intensity distributions. The cooling of the active gas to liquid nitrogen temperatures improved the output pulse energies 3 to 5 times on average. It was found that this intensity increase was caused mainly by the narrowing of the Raman linewidth upon cooling.     

Tunable UV-radiation by stimulated Raman scattering in hydrogen

We observed tunable UV radiation down to 175 nm by SRS of the output of a frequency-doubled dye laser in H₂. The high power output of the 4th anti-Stokes to 5th Stokes line generated by the frequency doubled dye laser and the 8th anti-Stokes to 3rd Stokes line generated by the undoubled dye laser represents a broadly tunable coherent radiation source between 189 nm and 2064 nm.     

Multi-wavelength Brillouin fiber laser using dual-cavity configuration

A simple technique for achieving multi-wavelength tunable multi-wavelength Brillouin fiber laser (BFL) based on dual-pass configuration is demonstrated. The BFL uses a piece of 10 km long non-zero dispersion shifted fiber (NZ-DSF) as a Brillouin gain medium to obtain odd-order Brillouin Stokes waves as an output with the line spacing of 0.16 nm (20 GHz) between each two consecutive waves by employing even-order Brillouin Stokes to improve output performance of the laser. With a BP of 15.3 dBm, at least 15 odd-order Brillouin Stokes and anti-Stokes lines are generated. The laser is room temperature stable, tunable over 50 nm wavelength range and has an optical signal to noise ratio of more than 30 dB at 1560 nm region. This Brillouin fiber laser can operate at any wavelength depending on the Brillouin pump (BP) wavelength used.     

Polarization enhancement of anti-Stokes emission in a para-H2 Raman laser

The effect of polarization can influence the frequency conversion and enhance the anti-Stokes emission in a rotational para-H₂ Raman laser. Stokes (16 μm) and anti-Stokes (7 μm) radiations were obtained from a line tunable CO₂ laser at 10 μm.     

Tunable infrared down-conversion in silver thiogallate

A ruby laser beam mixed in AgGaS₂ with the output of various ruby-pumped dye lasers has provided down-converted infrared radiation tuned from 4.6 to 12 μm. The measured phase-matching angles agree well with calculated values. Peak infrared powers of a few hundred milliwatts have been produced.     

Microstructure fibers as frequency-tunable sources of ultrashort chirped pulses for coherent nonlinear spectroscopy

Microstructure fibers are shown to allow the creation of new tunable sources for femtosecond nonlinear spectroscopy. These fibers provide a high efficiency of frequency upconversion of regeneratively amplified femtosecond pulses of a Cr:forsterite laser, permitting the generation of subpicosecond anti-Stokes pulses with a smooth temporal envelope and a linear positive chirp. These pulses from a microstructure fiber were used to measure the spectra of coherent anti-Stokes Raman scattering (CARS) of toluene solution by cross-correlating these pulses with the femtosecond second-harmonic output of the Cr:forsterite laser in boxcars geometry (XFROG CARS). PACS 42.65.Wi; 42.81.Qb     

Prism reflectors for high power lasers

A new type of laser reflector is described in which the laser beam is split by frustrated total internal reflection and the components combined again. It has the properties of high reflectivity, high damage resistance, wide bandwidth and variable reflectivity. The design of two particular reflectors is discussed and their performance evaluated. One of these reflectors has the property of lateral inversion of the reflected beam, which is found to aid transverse mode selection in a ruby laser. As an application of the reflectors, a damage free, single transverse mode, mode-locked ruby laser is described.     

A powerful broad band tunable dye laser

Perchloric acid solutions of 4 methylumbelliferone pumped by a second harmonic of ruby provide a high efficiency (20% conversion yield of pumping source) broad band (5600-4600 Å) tunable dye laser. Some effects of chemical quenching on the efficiency of this protonic exciplex laser were investigated.     

A tunable dye laser in the range 1.0–1.145 μ

A near IR tunable dye laser in the spectral range 1.0–1.145μ is described. Utilizing a 25 MW ruby laser pump, an output power in excess of 2 MW was obtained in the range 1.04–1.12μ while at 1.145μ the power was more than 100 kW.     

A picosecond near-infrared laser source based on a self-seeded optical parametric generator

We report on the design and development of a new type of near-IR laser source. The source comprises of an optical parametric generator (OPG) and a second harmonic generator (SHG) pumped by an 80-MHz, 1064-nm, 7-ps Nd:YVO₄ laser. The OPG is self-seeded with a fraction of its own signal output, which significantly enhances its conversion efficiency. The SHG doubles the frequency of OPG signal to produce a coherent output. The final output beam has a tunable wavelength near 800 nm, an average power of over 1 W, and a pulse duration around 5 ps. The M²-factor of the output beam can reach 1.1 after spatial filtering. With the new laser source, we have successfully demonstrated coherent anti-Stokes Raman scattering microscopy on 1 μm polystyrene beads, which shows that it has the potential to be a substitute for a picosecond optical parametric oscillator in certain microscopy or spectroscopy applications.     

Determination of the composition of mixtures of organic liquids by CARS spectroscopy

Two methods of realization of coherent anti-Stokes Raman scattering (CARS) spectroscopy of organic liquids are described: with a tunable dye laser and by means of biharmonic laser pumping based on stimulated Raman scattering. The second method is applied to liquids for the first time. The possibilities of the two methods are compared. CARS spectroscopy is applied for the first time to the analysis of a mixture of two organic liquids.     

Difference-frequency power generation in the 6.7–10.5 μm spectral region in very thin proustite crystals

Twenty watts of tunable, pulsed i.r. power in the 6.7–9 μm spectral region were generated from the difference frequency between the outputs from a Q-switched ruby laser and a tunable narrow-bandwidth, near-i.r. dye laser mixed in a 1-mm thick proustite crystal. The i.r. halfwidth was measured to be approx. 0.1 μm. At 10.5 μm, where there is strong absorption of radiation, 5 W of power were recorded.     

Operation of a high power,broadly tunable infrared dye laser

We discuss the operation and performance of a ruby pumped infrared dye laser with a wide tuning range and a high out-put power. The longitudinally pumped infrared laser was operated in the Littrow configuration without an intracavity beam expander. The dye, IR 125, exhibited a tunability range that extended from 8325 Å to 9375 Å. The dye laser had a pulse duration of 20 ns and an output power of 12.5 MW with a 2.3 joule ruby pump. The maximum output power of the infrared laser was limited by the damage threshold of the tuning element.     

Emission Spectra Inside the Ammonia s-Multiplets Pumped by a Line-Narrowed Tunable CO2 Laser

By using a line narrowed high power tunable laser we have analysed the FIR emission spectrum inside some , compact sQ, sR k-multiplets. Jumps between adjacent k-systems are observed , although tunable emissions of dominant lines are produced. The more favourable gain overlap of the K Raman lines in the fundamental vibrational level induces an off-resonance dominance of this process respect to the standard Raman scattering in the excited vibrational level. The AC Stark splitting has been also observed when the CO₂ laser is posed in resonance with the absorption lines.     

激光振荡器及放大器中受激布里渊散射相位共轭效应的实验研究

本文报道在激光振荡器和放大器中受激布里渊散射相位共轭效应的一系列实验研究。实验结果表明,受激布里渊散射的相位共轭特性有效的改善了激光光束质量,明显的提高了输出效率。文章并时实验结果进行了较为详尽的讨论。