Generation Of Picosecond Laser Pulses Research Articles

The Yb3+:LuAlO3 crystal as an active medium for picosecond mode-locked lasers

Herein, we report on the mathematical modelling and experimental study of the regime of nonsoliton mode locking in a laser based on the Yb3+:LuAlO3 (Yb:LuAP) crystal with longitudinal pumping by laser diode radiation. Simulation based on the Haus master equation permitted to determine the requirements for the parameters of a saturable absorber (SA), the level of the average output power, the size of the TEM00 mode of the cavity in the active element and on the gate to obtain a stable regime of generation of picosecond laser pulses. Laser experiments were carried out in a fourmirror X-shaped resonator using a semiconductor saturable mirror (SESAM) as a passive modulator and a laser diode with a fiber output of a maximum power up to 30 W at a wavelength of 978.5 nm as a pump source. We obtained a stable passive mode locking with a maximum average output power of up to 12 W and an ultrashort pulse duration of about 2 ps at an optical conversion efficiency of pump radiation into lasing radiation of about 38 %. Laser pulses were obtained at a central wavelength of about 999 nm with a minimum Stokes shift (about 2 %) with respect to the pump radiation, which significantly reduced the thermal load on the active element. Additionally, the preliminary results on the second harmonic generation and synchronous pumping of a parametric light generator using a Yb3+ : LuAlO3 crystal laser as a pump source are presented.

Programmable pulse synthesizer for the generation of Joule-level picosecond laser pulses of arbitrary shape.

We report the demonstration of a pulse synthesizer based on spatial beam splitting and pulse stacking for the generation of picosecond laser pulses of Joule-level energy with arbitrary shape. An array of liquid crystals is used to control the amplitude of ten individual sub-pulses, and sliding retroreflectors are used to adjust their temporal separations. The synthesizer was used in combination with a λ=1.03 µm diode-pumped cryogenically-cooled Yb: YAG chirped pulse amplification laser to synthesize 1.3 J pulses or pulse trains of arbitrary shapes up to 9 ns duration with a temporal resolution as short as 8 ps. This pulse synthesizer offers the opportunity to incorporate a self-learning system to search for the optimal laser pulse shapes for various applications including optimized plasma conditions in laser-plasma based soft x-ray lasers and plasma sources for extreme ultraviolet lithography.

Generation of picosecond laser pulses at 1030 nm with gigahertz range continuously tunable repetition rate.

We report on a watt range laser system generating picosecond pulses using electro-optical modulation of a 1030 nm single frequency low noise laser diode. Its repetition rate is continuously tunable between 11 and 18 GHz. Over this range, output spectra and pulse characteristics are measured and compared with a numerical simulation. Finally, amplitude and residual phase noise measurements of the source are also presented.

Generation of Picosecond Laser Pulses at 1064 nm from All Solid-State Passively Mode-Locked Lasers

Using semiconductor saturable absorber mirror and diode end-pumping configurations, all solid-state passively mode-locked Nd 3+ :YVO4 lasers have been successfully developed. The lasers efficiently provide a stable train of ultra-short laser pulses of 12 ps at 1064 nm at the pulse repetition rate adjustable from 8.8 MHz to 100 MHz. The peak power of 1.3 kW and an average laser power of 940 mW were obtained at the pulse repetitive rate of 60 MHz, corresponding to a laser conversion efficiency of 43%. In order to obtain lower pulse repetitive rate and, therefore, higher peak power, a long laser resonator (larger than 15 m) is proposed and successfully developed for diode end-pumped passively mode-locked laser operation using a simple multiple-pass cavity configuration. As a result, the peak laser power up to 5.1 kW was obtained at the pulse repetitive rate of 8.8 MHz. The experimental results of the picosecond laser amplification and the harmonic generations at 532 nm (2nd), 355 nm (3rd) and 266 nm (4th) are presented.

351 nm wavelength generation of picosecond laser pulses

The authors discuss 351 nm wavelength generation of picosecond laser pulses with a new CLBO crystal. 526.5 nm and 351 nm wavelength laser pulses with energy conversion efficiencies of 70 and 20% were obtained for the 3 ps fundamental laser pulse.

Picosecond laser pulse generation in a monolithic self- Q-switched solid-state laser

We report the generation of laser pulses of 290-ps duration with 8-μJ pulse energy in single longitudinal mode and single transverse mode in a diode-end-pumped monolithic self- Q-switched Cr,Nd:YAG laser.

Generation of short laser pulses

Progress in the technology of ultrashort pulse generation during the last years is outlined. After a short reminder of the basic active/passive mode locking processes and the combined pulse forming action of passive mode locking and gain saturation in the colliding-pulse mode locking arrangement (CPM), the recently developed coupled cavity/additive pulse mode locking (CCM/APM) configurations are reviewed. The Kerr lens mode locking (KLM) process constitutes an important advance towards simplicity and reliability. Its lack of a self-starting property has been of concern, but can finally be overcome by custom-built semiconductor nonlinear absorbers. Reduction of the thermal load of the active materials, higher output efficiencies and much enhanced beam quality result from the use of laser diodes to pump solid state lasers. Synchronisation of the process of picosecond laser pulse generation with an external signal with subpicosecond phase jitter is an important subject. As an illustration the CERN synchro laser system in use at the CLIC test facility for the generation of short electron bunches is presented. Possibilities for future improvements in this system as a consequence of recent technological advances are indicated.

Efficient phase-matched third harmonic light generation in hexafluoroisopropanol solutions of a pyrimidonecarbocyanine dye

The phase-matched collinear third harmonic generation of picosecond laser pulses in a 0.0825 molar hexafluoroisopropanol solution of a pyrimidonecarbocyanine dye is studied. The fundamental pulses are generated in a passively mode-locked Nd-phosphate glass laser. The saturation of third harmonic generation at high intensities is investigated. The influences of two-photon absorption, excited-state absorption, and amplified spontaneous emission are discussed. For input peak intensities above 1011 W/cm2 a third harmonic energy conversion of about 2×10−4 is achieved.

High-speed low-voltage ultraviolet light source

A novel quasi-spark gap has been designed and constructed with high-speed and low-spark voltage characteristics. Ultraviolet light generating sparks can be operated at a rate of up to 25 kHz with pulses as low as 28 V. The photon pulse has a rise time of <10 nsec. Negligible breakdown delay and subnanosecond jitter have also been observed. It is an efficient UV point source capable of fast triggering and synchronization. A UV photon generation efficiency of 10−3 was estimated. The spectral properties of this gap were also analyzed. This gap has been incorporated into a picosecond CO2 laser system to trigger a plasma shutter in the generation of picosecond laser pulses.

Fluctuation mechanism of ultrashort pulse generation by laser with saturable absorber

This paper presents a theoretical treatment of the fluctuation mechanism involved in the generation of picosecond laser pulses with saturable absorbers. The processes responsible for the shortening of the pulsewidth and for selection of the most intense pulse are treated. Some experimental results that confirmed the treatment are presented. The influence of inertia of saturable absorber and nonlinear losses (self-focusing and self-modulation) is discussed.

Efficient Second Harmonic Generation of Picosecond Laser Pulses

Efficient conversion to the second harmonic (SH) using KD2PO4 and CsH2AsO4 crystals inside a folded cavity of a high-power-dye mode-locked Nd3+: glass laser is reported. For the first time, frequency-doubled picosecond light pulses have been obtained in CsH2AsO4 with peak powers of the order of 109 W/cm2 at 0.531 μ for an effective pump power density of 4×109 W/cm2.

Picosecond laser pulses

The broad bandwidth and long storage lifetimes of Nd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> : glass and ruby lasers have made possible the generation of picosecond laser pulses having peak powers it excess of one gigawatt and repetition rates in the microwave range. The numerous application areas of these pulses include research in nonlinear optics, transient response of atomic and molecular systems, optically generated plasmas, spectroscopy, ranging, optical information processing, and high-speed photography. This paper reviews several experimental techniques for generating, measuring, and utilizing these ultrashort laser pulses.