Diode-pumped Nd:YAG master oscillator power amplifier with high pulse energy, excellent beam quality, and frequency-stabilized master oscillator as a basis for a next-generation lidar system

A pulsed, diode-laser-pumped Nd:YAG master oscillator power amplifier (MOPA) in rod geometry, frequency stabilized with a modified Pound-Drever-Hall scheme is presented. The apparatus delivers 33-ns pulses with a maximum pulse energy of 0.5 J at 1064 nm. The system was set up in two different configurations for repetition rates of 100 or 250 Hz. The beam quality was measured to be 1.5 times the diffraction limit at a pulse energy of 405 mJ and a repetition rate of 100 Hz. At 250 Hz with the same pulse energy, the M2 was better than 2.1. The radiation is frequency converted with an efficiency of 50% to 532 nm. This MOPA system will be the pump laser of transmitters for a variety of high-end, scanning lidar systems.     

High-energy hybrid Raman optical parametric amplifier eye safe laser source

A high-energy eye safe laser source at 1.54 μm is demonstrated experimentally by using a hybrid system of stimulated Raman scattering and optical parametric amplification pumped by a single 1.06-μm Nd:YAG laser source. This system overcomes some of the technical problems that occur in conventional eye safe lasers, such as optical breakdown and thermal blooming in the Raman laser, and thermal conduction problems in the erbium-doped glass solid-state laser that limit the repetition rate when high-energy output is sought. Thus this hybrid design provides a simple system that could provide a high pulse energy output (> 50 mJ) at a repetition rate of greater than 10 Hz.     

Development of a chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research

A chirped pulse amplification laser with zigzag slab Nd:glass amplifiers dedicated to x-ray laser research is described. The laser provides a 1.6 ps duration pulse with approximately 7 J energy at a repetition rate of 0.1 Hz. In the power amplifier system, laser light is amplified in a two-step manner: The first step is image-relayed multipass amplification up to approximately 1 J with a 10 mm x 10 mm beam. The second step is double-pass amplification up to >10 J with a 10 mm x 90 mm beam. By using this laser system, the saturated amplification of the Ni-like Ag laser at a wavelength of 13.9 nm has been successfully demonstrated.     

500 Hz ultraviolet dye laser with pulse energy 1.7 mJ and potential for PLIF imaging

ABSTRACT

This paper describes a high-pulse-energy frequency-doubled ultraviolet dye laser operating at a repetition rate of 500?Hz. The pump source is a laser-diode side-pumped Q-switched Nd:YAG laser with a pulse energy of 29?mJ at 532?nm. A master oscillator power amplifier is employed to amplify the output pulse of the dye laser to 8.1?mJ at 566?nm, and by frequency doubling with BBO crystal a pulse energy of 1.7?mJ at 283?nm is achieved with a pulse width of 8?ns. This is more than four times the largest reported pulse energies generated by other fixed-frequency dye lasers when operating at repetition rates of more than 1?kHz. The conversion efficiency and stability of dye laser are discussed, which show the potential for high-speed laser diagnostics in the fields of combustion and turbulent flow detection.     

Theoretical and experimental investigations of injection-locked signal extraction of Tm:YAG laser

Injection-seeded is an effective method to obtain high-power pulsed laser with pure spectrum, which is useful to be the laser source of a coherent Doppler LIDAR or a differential absorption LIDAR. In order to achieve the useful injection-locked signal, mode matching between master laser and slave laser is necessary. In this paper, various factors influencing on the extraction of injection-locked signal are analyzed theoretically. Then, experiments on an injection-seeded Tm:YAG laser are carried on, and injection-locked signal is extracted successfully. Moreover, an injection-seeded Tm:YAG laser is achieved, with pulsed single-frequency at 2013 nm, output energy of 3.16 mJ, and pulse width of 238.7 ns, at a repetition rate of 100 Hz.     

Development of a compact efficient 10 Hz 20 TW Ti:sapphire laser system with a 1 kHz regenerative amplifier

We have constructed a compact efficient Ti:sapphire laser system that generates 30 fs, 630 mJ pulses at a repetition rate of 10 Hz. A new geometry for a single-stage multipass power amplifier is proposed that greatly weakens and even makes use of thermal lensing. Such geometry can realize high output in a single-stage power amplifier; otherwise at least two-stage power amplifiers are required. The new configuration simplifies the laser system and reduces the cost. The key point in this design is that the beam spot size evolution is considered in combination with the pulse amplification.     

Single-frequency pulsed laser source with hybrid MOPA configuration

A unique approach with a hybrid master oscillator power amplifier configuration to obtain single-frequency, high-energy laser pulses at 1064 nm is presented. The setup consists of a single-frequency seed laser, a multistage fiber amplifier, and a four-pass crystal rod amplifier. Pulse energy of 10 mJ is obtained at the repetition rate of 100 Hz. The pulse width is about 110 ns with a transform-limited linewidth of 3.2 MHz. The M(2) factor of the output beam is about 1.5. To our knowledge, this is the first report of using a hybrid amplifier to obtain 10 mJ pulses with long pulse width and transform-limited linewidth.     

Simultaneous Mode Locking in a Diode-Pumped Passively Q-Switched Nd:YVO(4) Laser with a GaAs Saturable Absorber

Simultaneous mode locking and Q switching is accomplished in a diode-pumped Nd:YVO(4)/GaAs laser. The average output power is ~2.0 W at 10.6-W absorbed pump power, and the repetition rate of the Q-switched pulse is ~120 kHz. The mode-locked pulse inside the Q-switched pulse has a repetition rate of ~148 MHz, and its average duration is estimated to be ~100 ps.     

Optimisation of GaAs nanocrystals synthesis by laser ablation in water

Laser ablation of a gallium arsenide (GaAs) wafer immersed in distilled water was carried out using the fundamental wavelength of a high frequency Nd:YAG laser with 240?ns pulse duration. Rate of nanoparticles generation through laser ablation for various amounts of laser pulse energies (0.4–0.94?mJ) and repetition rates (400–2000?Hz) were studied and a maximum ablation rate of 19.6?µgr/s was obtained. Formation of the pure GaAs nanocrystals (NCs) is confirmed using TEM micrograph and X-ray diffraction analysis. Band-gap energy of generated GaAs NCs is calculated by Tauc method to be between 2.48 and 2.60?eV which is larger than the band-gap energy of bulk GaAs. The band-gap energy of NCs is increased by increasing the energy of laser pulses and is decreased by increasing the pulse repetition rate.     

High-energy picosecond near-vacuum ultraviolet pulses generated by sum-frequency mixing of an amplified Ti:sapphire laser

We demonstrate high-energy picosecond near-vacuum ultraviolet laser pulse generation. Frequency quadrupling is achieved by noncollinear sum-frequency mixing of the fundamental and the third harmonic of a two-stage Ti:sapphire amplifier in beta-BaB(2)O(4) crystal. UV pulses with energies of approximately 10 mJ tunable from 195 to 210 nm at a 10 Hz repetition rate are obtained.     

Laser rockets

The results of experimental and theoretical investigations of the dynamic characteristics of a laser rocket in the initial flight path segment are presented. The energy to a laser jet propulsor was delivered with the beam of a CO-or CO₂-pulsed laser with a pulse energy ranging from 0.1 to 3.0 kJ at a repetition frequency of 100 Hz.     

Pulse compression with a high-energy Nd:YAG regenerative amplifier system

We describe a method for the generation of readily synchronizable, near-transform-limited, 1064-nm, 6-mJ pulses with <20-ps duration at a repetition rate of 20 Hz. The method employs chirped pulse amplification of spectrally broadened and temporally stretched pulses from a cw mode-locked Nd:YAG laser in a commercial Nd:YAG regenerative amplifier followed by pulse compression with a grating pair. Linear amplification subsequent to regenerative amplification is not required with this method, although higher energies would be easily obtained.     

Diode-end-pumped electro-optically Q-switched Nd:YLF slab laser

We report a very compact Nd:YLF slab laser that is end pumped by a quasi-continuous-wave diode stack. A hybrid resonator is used to generate high output power in a near-diffraction-limited beam (i.e., a beam propogation M2 factor of less than 1.2). A pulse energy of 14.3 mJ was obtained with a pulse width of 8.5 ns at a repetition rate of 500 Hz, which corresponds to a Q-switched peak power of 1.68 MW.     

Passively Q-switched Yb3+:YCa4O(BO3)3 laser with InGaAs quantum wells as saturable absorbers

A diode-pumped Yb:YCOB laser at 1086 nm is passively Q switched by using InGaAs quantum wells as saturable absorbers and utilizing the Bragg mirror structure as an output coupler. With an absorbed pump power of 9.2 W the laser produces pulses of 100 ms duration with average pulse energy of as much as 165 microJ at a pulse repetition rate of 7 kHz.     

Yb:S-FAP lasers

It has recently been reported that several high power, diode-pumped laser systems have been developed based on crystals of Yb:S-FAP [Yb³⁺:Sr₅(PO₄)₃F]. The mercury laser, at Lawrence Livermore National Laboratory, is the most prominent system using Yb:S-FAP and is currently producing 23 J at 5 Hz in a 15 nsec pulse, based on partial activation of the system. In addition, a regenerative amplifier is being developed at Waseda University in Japan and has produced greater than 12 mJ with high beam quality at 50 Hz repetition rate. Q-Peak has demonstrated 16 mJ of maximum energy/output pulse in a multi-pass, diode side-pumped amplifier and ELSA in France is implementing Yb:S-FAP in a 985 nm pump for an EDFA, producing 250 mW. Growth of high optical quality crystals of Yb:S-FAP is a challenge due to multiple crystalline defects. However, at this time, a growth process has been developed to produce high quality 3.5 cm diameter Yb:S-FAP crystals and a process is under development for producing 6.5 cm diameter crystals.     

Megahertz-repetition-rate Nd:glass fiber laser

Stable trains of 100-200-ns-long pulses are obtained at 0.46-1.06-MHz repetition rates in a Nd:glass fiber laser by driving large-amplitude relaxation oscillations at or below their resonance. Numerical simulations agree qualitatively with temporal profiles of the output power. We show that the maximum pulse-repetition rate of a relaxation-oscillation laser increases as the square root of pump power at low P and that its theoretical upper limit is close to the pulse rate of a mode-locked laser.     

Sum-Frequency Generation of Femtosecond Pulses in CsLiB(6)O(10) Down to 175 nm

Using a 150-mum-thick CsLiB(6)O(10) crystal, we produced 100-fs, >200-nJ light pulses tunable between 175 and 180 nm by sum-frequency generation at a 1-kHz repetition rate with an all-solid-state laser system mixing the fourth harmonic of a femtosecond Ti:sapphire regenerative amplifier and the idler pulse from a traveling-wave optical parametric amplifier.     

InGaAs quantum-well saturable absorbers for a diode-pumped passively Q-switched Nd:YAG laser at 1123 nm

A low-loss semiconductor saturable absorber based on InGaAs quantum wells was developed for highly efficient Q switching of a diode-pumped Nd:YAG laser operating at 1123 nm. With an incident pump power of 16 W, an average output power of 3.1 W with a Q-switched pulse width of 77 ns at a pulse repetition rate of 100 kHz was obtained.     

Laser synthesis of nanopowders with yttrium aluminum garnet stoichiometry

A nanopowder of yttria-alumina mixture with the yttrium aluminum garnet (YAG) stoichiometry has been synthesized for the first time by the laser evaporation method. A high-power CO₂ laser with pulse duration above 200 μs, repetition frequency of 500 Hz, and pulse energy of about 1 J provided a high yield of powder at a rate of 24 g/h. The obtained nanopowder has been used to prepare YAG:Nd³⁺ ceramics with a cubic structure possessing an optical transmittance of about 77% at a wavelength of 1.06 μm. The successful synthesis of YAG nanopowder is based on the preliminary numerical simulation of the laser evaporation of a target using a three-dimensional model.     

Nonlinear Optical Characteristics of C60 Thin Films

Abstract

The results of investigation of the real and imaginary parts of third‐order nonlinear susceptibility (χ⁽³⁾) of C₆₀ thin films (～100 nm) at the wavelength of Nd: YAG laser radiation (532 nm, τ = 55 ps) are presented using Z‐scan technique. Our studies show that the sign of Reχ⁽³⁾ changes from negative, at pulse repetition rate of 2 Hz to positive, at 0.5 Hz. Sign variations of the real part of the third‐order susceptibility were attributed to the influence of the thermal lens.