YAG Pump Laser Research Articles

Efficient conversion of a 1064 μm Nd:YAG laser to the eye-safe region using a diamond Raman laser

We report an efficient 1.485 μm external cavity diamond Raman laser operating on the 2nd Stokes shift of a 1.064 μm Nd:YAG pump laser. 1.63 W pulsed at 5 kHz is produced with a quantum conversion efficiency of 71% and excellent beam quality. Numerical modelling confirms that optimal operation is achieved with low output coupling reflectivity.

High-energy, phase-stable, ultrabroadband kHz OPCPA at 2.1 μm pumped by a picosecond cryogenic Yb:YAG laser.

We report on a kHz, mJ-level, carrier-envelope phase (CEP)-stable ultrabroadband optical parametric chirped-pulse amplifier (OPCPA) at 2.1-μm wavelength, pumped by a high-energy, 14 ps, cryogenic Yb:YAG pump laser, and its application to high-order harmonic generation (HHG) with Xe. The pre-amplifier chain is pumped by a 12-ps Nd:YLF pump laser and both pump lasers are optically synchronized to the signal pulse of the OPCPA. An amplified pulse energy of 0.85 mJ was obtained at the final OPCPA stage with good beam profile. The pulse is compressed to 4.5 optical cycles (<32 fs) with a spectral bandwidth of 474 nm supporting 3.5 optical cycles. The CEP stability was measured to be 194 mrad and the super-fluorescence noise is estimated to be ~9%. First HHG results are demonstrated with Xe showing significant cutoff extension to >85 eV with an efficiency of ~10-10 per harmonic, limited by the maximum gas pressure and flow into the chamber. This demonstrates the potential of this 2.1-μm source for scaling of photon energy and flux in the water-window range when applied to Ne and He at kHz repetition rate.

Determination of Physicochemical Parameters of Ionic Liquids and Their Mixtures with Solvents Using Laser-Induced Gratings

The laser-induced gratings (LIGs) technique has been applied for the simultaneous determination of sound speed and thermal diffusivity in the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate, [EMIm][EtSO(4)], its mixture with 85.68 mol % acetone, C(3)H(6)O, and pure acetone. The measurements have been performed in a quartz glass cuvette at ambient pressure and temperature. Radiation of a pulse-repetitive Q-switched Nd:YAG pump laser (1064 nm) effected quasi-resonant excitation of overtone-combinational vibrational states of the RTIL molecules followed by the appearance of laser-induced gratings. The temporal evolution of the transient gratings (oscillation and damping) was recorded using Bragg-diffraction of a continuous-wave probe laser radiation. From the LIG signals' temporal profiles, values of the sound speed and thermal diffusivity were determined and, in addition, the isentropic compressibility and thermal conductivity were derived. The results are in a reasonable agreement with those reported in the literature. Furthermore, since the data for the determination of the physicochemical properties can be obtained with a single laser pulse, the LIG technique has potential for applications where data acquisition at high repetition rates is desirable for example to monitor processes.

10-mJ optically synchronized CEP-stable chirped parametric amplifier at 1.5 μm

We demonstrate the generation of 10-mJ 1.5-μm few-cycle pulses from a 4-stage OPCPA system. The system is based on a fusion of femtosecond DPSS Yb technology and a picosecond Nd:YAG pump laser. In a first preliminary filamentation experiment in argon at 5 atm, we observe significant spectral broadening of the recompressed multi-mJ 1.5-μm pulses. The filamentation output spectrum supports the generation of 8 fs pulses equivalent to sub-to-cycle pulses at 1.5 μm. We foresee that our terawatt-peak-power sub-to-cycle pulse source will open the door to exciting new experiments in attosecond high-field science in the near future.

The ISOLDE RILIS pump laser upgrade and the LARIS Laboratory

On account of its high efficiency, speed and unmatched selectivity, the Resonance Ionization Laser Ion Source (RILIS) is the preferred method for ionizing the nuclear reaction products at the ISOLDE on-line isotope separator facility. By exploiting the unique electronic energy level ‘fingerprint’ of a chosen element, the RILIS process of laser step-wise resonance ionization enables an ion beam of high chemical purity to be sent through the mass selective separator magnet. The isobaric purity of a beam of a chosen isotope is therefore greatly increased. The RILIS, comprising of up to three frequency tunable pulsed dye lasers has been upgraded with the installation of a Nd:YAG pump laser as a replacement for the old Copper Vapor Laser (CVL) system. A summary of the current Nd:YAG pumped RILIS performance is given. To accompany the RILIS pump laser upgrade, a new ionization scheme for manganese has been developed at the newly constructed LAser Resonance Ionization Spectroscopy (LARIS) laboratory and successfully applied for on-line RILIS operation. An overview of the LARIS facility is given along with details of the ionization scheme development work for manganese.

Self-compression of millijoule 15 μm pulses

We demonstrate a four-stage optical parametric chirped-pulse amplification system that delivers carrier-envelope phase-stable approximately 1.5 microm pulses with energies up to 12.5 mJ before recompression. The system is based on a fusion of femtosecond diode-pumped solid-state Yb technology and a picosecond 100 mJ Nd:YAG pump laser. Pulses with 62 nm bandwidth are recompressed to a 74.4 fs duration close to the transform limit. To show the way toward a terawatt-peak-power single-cycle IR source, we demonstrate self-compression of 2.2 mJ pulses down to 19.8 fs duration in a single filament in argon with a 1.5 mJ output energy and 66% energy throughput.

Spectroscopic System for Direct Lanthanide Photoluminescence Spectroscopy with Nanomolar Detection Limits

A new spectroscopic system for direct photoluminescence of lanthanide ions (Ln(III)) through electronic transitions within the 4f(n) manifold is described. The system is based on an injection seeded frequency tripled (lambda = 355 nm) Nd:YAG pump laser coupled with a master oscillator power oscillator (MOPO). The MOPO delivers an average pulse energy of approximately 60 mJ/pulse, is continuously tunable from 425 to 690 nm (Signal) and 735 to 1800 nm (Idler) with a linewidth of <0.2 cm(-1), and has a pulse duration of 10-12 ns. Aqueous solutions containing two polyaminocarboxylate complexes, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA), and Ln(3+) aqua ion for several lanthanides including Eu(III), Tb(III), Dy(III), and Sm(III)) are used as steady-state and time-resolved photoluminescence standards. The versatility of the instrument is demonstrated by excitation scans over a broad visible range for aqueous solutions of complexes of Eu(III), Dy(III), Sm(III), and Tb(III). The Eu(III) excitation band ((7)F(o)-->(5)D(o)) is recorded over a range of complex concentrations that are 1000-fold less than reported previously, including Eu(EDTA) (1.00 nM), Eu(DTPA) (1.00 nM), and Eu(III) aqua ion (50.0 nM). Emission spectra are recorded in the visible range for Ln(III) complexes at pH 6.5 and 1.00 mM. Excited-state lifetimes for the standards were constant as a function of concentration from 10.0 nM to 1.00 mM for Eu(EDTA) and Eu(DTPA) and from 100 nM to 1.00 mM for Eu(III) aqua ion. Photoluminescence lifetimes in H(2)O and D(2)O are recorded and used to calculate the number of bound water molecules for all complexes.

High-resolution infrared polarization spectroscopy and degenerate four wave mixing spectroscopy of methane

High-resolution infrared polarization spectroscopy (IR-PS) and degenerate four wave mixing (IR-DFWM) spectroscopy of methane using a diode-seeded modeless laser (DSML) system are reported. Mid-infrared radiation around 3.3 μm is generated by difference frequency mixing of the single-mode output of the DSML around 0.634 μm with the frequency-doubled output of a single-mode Nd:YAG pump laser at 0.532 μm. Polarization spectroscopy signals in the forward geometry were generated in methane at around 5 Torr pressure. IR-PS spectra were recorded with a typical signal-to-noise ratio of 150:1 with methane pressures of at least 1 Torr. The line shape of the IR-PS signals was analysed to measure pressure broadening induced by nitrogen buffer gas yielding a value of 6.3±1.5 MHz Torr−1. IR-DFWM spectra of methane were generated in the counter-propagating pump geometry yielding Doppler-free signals with signal-to-noise ratios of typically 650:1. Signals were obtained at methane pressures down to less than 10 mTorr. A comparison of IR-PS and IR-DFWM is made indicating that IR-DFWM has some advantages over IR-PS in this spectral region in terms of sensitivity, signal-to-noise ratio and ease of use. The results illustrate the utility of the DSML for high-resolution nonlinear spectroscopy in the mid infrared.

4th Wave of Modernization by Photon/Electron Technology and Development of Advanced Laser Integrated Manufacturing System (ALIMS)

High power lasers, including CO2 laser, Nd:YAG laser, Excimer laser, Diode laser, LD pumped YAG laser, LD pumped Disk laser, LD pumped Fiber laser and Femto second laser, are now used as a modern tool for industries as well as a computer alike in the 4th wave of modernization. Lasers are currently used for welding, cutting, drilling, cladding, direct fabrication, marking, cleaning, micro-machining peening and forming of materials in modernized factories. The joining speed (= product of welding speed and penetration depth) of 45,000mm2/min for steel sheet can be obtained by a 10kW Yb: fiber laser and is that of 50kW electron beam welding, which require the vacuum chamber. As a result of large numbers of research and developments the Advanced Laser Integrated Manufacturing System (ALIMS) using high power diode lasers has been developed and used for modernization in many industrialized countries. The laser materials processing is now penetrated as a machining tool into many industries. In the present paper, an advanced laser integrated manufacturing systems and its applications to industries such as automotive, electronics, ship building and steel making industry are introduced. In addition, development of an advanced laser integrated manufacturing system using a 2kW fiber laser for welding a car panel and “Laser Roll Welding” system for dissimilar metal joints such as mild steel/high strength steel to aluminium alloys, titanium to aluminium and steel to titanium, is described for modernization of industries. It will be a magnificent for the industries. And the 4th wave of modernization and opto-mechatronics will be promoted more by laser/photon technology in the future.

Single-frequency coherent terahertz-wave generation using two Cr:forsterite lasers pumped using one Nd:YAG laser

We have developed a compact terahertz-wave generator using two small Cr:forsterite lasers with single Nd:YAG laser pumping based on difference frequency generation in a GaP crystal. A Cr:forsterite laser was constructed with diffraction gratings, by which the pulse duration and delay time of the Cr:forsterite laser depend on the Cr:forsterite laser energy and the cavity length. The Cr:forsterite laser energy was tuned using the optical alignment and pumping energy. Temporal overlap of two Cr:forsterite laser pulses was realized at the GaP crystal. A single-frequency terahertz wave was generated at energy of 4.7 pJ around 2.95 THz using a 30-cm-long Cr:forsterite laser system.

Broadly tunable ultraviolet miniature cerium-doped LiLuF lasers

Ultraviolet (UV) miniature cerium fluoride lasers have been demonstrated using a low cost, frequency-quadrupled microchip Nd:YAG pump laser. The use of miniature laser cavities was shown to significantly improve the laser performance in the low pump power region. We have achieved slope efficiencies up to 70% and pump thresholds as low as 100 nJ. Continuous tuning from 306 nm to 338 nm was achieved using a Brewster angle prism.

Control of amplified optical parametric fluorescence for hybrid chirped-pulse amplification

The amplified optical parametric fluorescence from an optical parametric chirped-pulse amplifier (OPCPA) was controlled by injecting a residual fundamental pulse from a seeded Q-switched Nd:YAG pumping laser as a quenching beam. The output pulse from the OPCPA was used as a seed pulse for a Ti:sapphire chirped-pulse amplifier system to generate over 10 TW peak power with a high contrast ratio.

Control of Amplified Optical Parametric Fluorescence in Optical Parametric Chirped Pulse Amplification and High Power Optical Pulse Generation

The amplified optical parametric fluorescence (AOPF) from optical parametric chirped-pulse amplifier (OPCPA) was controlled by injecting a residual fundamental pulse from a seeded Q-switch Nd: YAG pumping laser, as a quenching beam. The output pulse from the OPCPA was used as a seed pulse for Ti: sapphire chirped pulse amplifier (CPA) system to generate over 10TW peak power with a high contrast ratio.

High-power optical parametric chirped-pulse amplifier system with a 155??m signal and a 1064??m pump

We have designed and built a chirped-pulse parametric-amplifier system that utilizes a 10 Hz, 300 ps, Nd:YAG pump laser system; a 1.575 microm fiber oscillator and amplifier as the signal source; and rubidium titanyl phosphate and potassium titanyl arsenate nonlinear crystals. We obtained 260 fs, 30 mJ pulses centered at 1.550 microm, representing a gain of > 10(9) and a peak power of 100 GW. To our knowledge, these are the highest energy and peak power pulses ever produced in the 1.5-2.0 microm region

Highly efficient Raman conversion in O2 pumped by a seeded narrow band second-harmonic Nd:YAG laser

The first-Stokes conversion efficiency for a stimulated Raman scattering (SRS) is usually very low in gaseous oxygen media. In 3.0 Mpa O2, a single longitudinal mode second harmonic Nd:YAG laser pump source gives a typical vibrational first-Stokes conversion efficiency of only 2.5%, In comparison, the accompanying stimulated Brillouin scattering (SBS) attains a reflectivity of 67%. However, by seeding an OPO beam into the Raman cavity, the first-Stokes photon conversion efficiency now attains a peak value of 54%, while the SBS reflectivity reduces to 5% in a 6.1 Mpa 41:59 O2/ He mixture. This 54% efficiency was obtained for a seeder laser pulse-width less than one half that of pump laser (6.8 ns). A first-Stokes peak power conversion efficiency as high as 88% has been obtained when the pump and seeder pulse peaks coincide. So, we may expect a higher first-Stokes photon conversion efficiency if the seeder pulse-width can be made equal to or larger than that of the pump pulse. On the other hand, the beam quality of the first-Stokes in an O2/ He mixture excels that of the pump laser for a seeder energy of 5 mJ and pump energy of 50 mJ. However, at pump energies higher than 105 mJ and a pump laser repetition rate of 10 Hz, the thermal defocusing effect worsens the first-Stokes beam quality. This thermal defocusing effect is a result of the Raman heat release and could be eliminated by fast circulating and cooling the Raman gas medium.

Focus on Lasers and Optics

Focus on Lasers and Optics

High‐efficiency stimulated Raman scattering from alcohols: theory and experiments

AbstractThe coherent Raman emission from primary alcohols [CH3(CH2)nOH, n = 0–10], 2‐propyl alcohol and tert‐butyl alcohol was studied using a frequency‐doubled Nd:YAG pump laser (532 nm). We show that increases in the chain length (CH2 groups) and the number of CH3 groups in the alcohols (CH3 &gt; CH2) enhance the Raman emission efficiency. Theoretical density functional theory (DFT) calculations and frequency scaling allow one to associate the vibrational wavenumbers with the molecular fragment responsible for the vibration. We obtained good agreement between the observed phenomena and the predictions of the theory. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Soliton-based pump-seed synchronization for few-cycle OPCPA

We demonstrate a significant simplification of the scheme for few-cycle Optical Parametric Chirped Pulse Amplification (OPCPA) which results in the elimination of a picosecond's master oscillator and electronic synchronization loops. A fraction of a broadband seed pulse centered at 760 nm from a 70-MHz Ti:sapphire oscillator was frequency-shifted in a photonic crystal fiber to enable synchronized seeding of a picosecond's Nd:YAG pump laser. The seed radiation at 1064 nm is produced in the soliton regime which makes it inherently more intense and stable in comparison with other methods of frequency conversion. The remaining fraction of the Ti:sapphire output is amplified with a FWHM bandwidth of 250 nm in a single timing-jitter-free OPCPA stage. Our work opens up the exciting possibility to use sub-picosecond's pump pulses from highly efficient Yb-based amplifiers for jitter-less parametric amplification of carrier-envelope phase stabilized pulses from Ti:sapphire oscillators.

Single-mode Raman fiber laser based on a multimode fiber.

Single-mode operation of a Raman fiber laser based on a multimode fiber has been demonstrated for what is to our knowledge the first time. Single-mode operation was achieved through the beam cleanup effect of stimulated Raman scattering in multimode fibers. The Raman laser, consisting of a 50-microm-core multimode fiber and a multimode Nd:YAG laser pump, produced an output beam corresponding to the fundamental mode of the fiber.

Measurement of gain and evaluation of photon avalanche efficiency in 10% Tm:KY(WO 4) 2 crystal pumped by free-running Nd:YAG laser

The gain at 1831 nm and 3 F 4 excited state relaxation were measured with 10%- and 15% Tm:KYW crystals under free-running Nd:YAG laser pumping. The emission cross-section calculated from the gain data is in a reasonable agreement with that of from the fluorescence spectra. The population of 3 F 4 manifold and the photon avalanche efficiency depending on the absorbed pump energy are reported also.