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In this work we report on the output performances of a Nd:YVO4 picosecond (ps) laser oscillator that was passively modulated by different semiconductor saturable absorber mirrors (SESAMs). The laser emission characteristics are given for SESAM used in Z-type and W-type cavities under similar pumping conditions. Q-switch mode-locking (QML) regime was obtained in the Z-type resonator whereas the W-type oscillator enabled stable mode-locking (ML) operation. For the W-type cavity ML performances are reported for two SESAMs with distinct parameters. Thus the use of a SESAM with 10 ps long recovery time allowed ML operation with pulses of 11.1 nJ energy and 15 ps duration (0.74 kW peak power) at 158 MHz repetition rate; the average power at 1.06 μm was 1.75 W for 5.17 W pump power at 809 nm. Employing a second SESAM with 0.5 ps short recovery time, the Nd:YVO4 laser yielded pulses with increased 13.4 nJ pulse energy and shorter, 12.5 ps, duration (1.1 kW peak power) at 158 MHz repetition rate, corresponding to 2.11 W average power; the pump power was 5.09 W. The results highlight the significant role of the SESAM parameters as well as of the implemented cavity design for the construction of a ps laser source of high performance.

A 500 kHz burst-mode YVO4/Nd:YVO41064 nm laser oscillator with a burst duration of 1 ms and a burst energy of 45.0 mJ was presented. The acousto-optically Q-switched frequency could be varied from 10 kHz to 500 kHz, resulting in 10–500 sub-pulses per burst. At the pulse repetition rate of 500 kHz, the maximum single pulse energy reached 90.0 μJ with a pulse width of 37.8 ns, corresponding to a peak power of 2.4 kW. The beam quality factor of burst-mode laser at 500 kHz was measured to be M2=1.6. The burst-mode YVO4/Nd:YVO4laser could be acted as a master oscillator for further power scaling.

We have successfully applied intermode beating mode-locking (IBML) for short pulse generation in compact Tm3+-doped double clad fiber lasers (TDFLs). This IBML technique is implemented by longitudinal-mode frequency matching between pump source and laser oscillator without extra mode-locker. Here, the achieved IBML TDFLs can respectively generate 2056.47 nm, 2003.88 nm and 1963.79 nm short pulses. Their output characteristics have been respectively investigated. The IBML technique enables the large pulse energy of ~20.8 nJ with pulse repetition rate of ~9.6 MHz. This work may open a new route for next-generation of high performance mid-infrared short-pulse all-fiber laser sources.

The European X-ray Free-Electron Laser will generate high energy light pulses in the femto-second range. A clock signal, which synchronizes all components, is distributed via laser pulses. The accuracy of these laser pulses is crucial to achieve precise measurements which are needed to control the Free-Electron Laser. In order to reach the maximum performance, advanced model-based control approaches are used to compensate external influences. This paper shows the modeling of the Master Laser Oscillator by fractional order systems, which improve known approaches to system modeling by providing a higher accuracy.

We report results of a systematic study of the morphology of laser-written structures within transparent media like fused silica, borosilicate glass (BK7), and polymethylmethylacrylate (PMMA) using a high-energy, 5.1 MHz repetition rate, femtosecond laser oscillator. Depending on experimental conditions, both smooth channels as well as dot patterns can be laser-written. The periodicity of the written dots is readily controlled by the energy dose, a single parameter that encompasses laser energy, translation speed at fixed repetition rate, and focusing conditions. We discover the importance of the direction in which laser-writing is carried out: the periodicity of the dot patterns written at fixed energy dose but with opposite writing directions is significantly different. In PMMA, extremely large rod-like structures (∼200 µm) are observed whose formation is also dependent on writing direction. We quantify guidance of 632 nm and 830 nm light in structures written in BK7.

Experimental results of a study on the wavelength dependence and the dynamic range of the quadratic response of commercial grade light emitting diodes (LEDs) are reported over a broad spectral range of 680 nm to 1080 nm using ~ 100 fs duration laser pulses from cw mode locked laser oscillator. A large dynamic range of the quadratic response has been demonstrated in a reverse biased LED. The observed dynamic range compares well with that obtained using a biased photomultiplier tube with large internal gain.

In this paper, we present the concept of a microelectromechanical systems ring laser gyroscope (MEMS-RLG) and its optical components. MEMS-RLG has a semiconductor optical amplifier (SOA) enclosed with mirrors that form an optical loop for an external laser oscillator in free space. To confirm the feasibility of MEMS-RLGs, we constructed an experimental device with commercially available SOA and mirrors for external oscillation. We also show the fabrication and characteristics of optical components such as movable mirrors and a lens-positioning device, which are required for a miniaturized MEMS-RLG.

We propose a new method for the determination of the pumping coefficient dependence upon the variation of the flashlamp opacity in a pulsed Nd:YAG laser oscillator which cannot be determined by existing methods. The method that we propose is based on the measure of the build-up time during which the excited-state population is being pumped up to its threshold lasing value.

An experimental and theoretical study of a high repetition rate laser source operating on a novel mode-locking technique is presented. This technique relies on the fast saturation and recovery of a semiconductor optical amplifier induced by an external optical pulse and has been used to obtain 4.3 ps pulses at 20 GHz. A complete mathematical model of the fiber ring laser is presented describing the mode-locking process in the laser oscillator and providing solutions for the steady-state mode-locked pulse profile. The critical parameters of the system are defined and analyzed and their impact on the formation of the mode-locked pulses is examined. The comparison between the theoretical results and the experimental data reveals very good agreement and has allowed the optimization of the performance of the system in terms of its critical parameters.

Feedback control of cavity detuning length in a short-pulse free-electron laser oscillator system is suggested and numerical simulation results are presented. By changing the detuning length with reference to the position of the optical pulse at the end of every pass, the system operation is very stable, and very high power and comparably good spectral characteristics have been achieved. Feasibility of this scheme is also discussed.

We simulate the transient behaviour of a self-starting holographic laser oscillator using a numerical model which can account, to arbitrary strength, for one, two and four gain gratings within the saturable amplifying medium. The dependence of output energy on parameters such as intracavity gain and output coupler reflectivity is investigated, thereby enabling the optimisation of extraction efficiency and the understanding of oscillation and grating dynamics.

Lidar is one of the key sensors to understand global atmospheric environment, so lidar is one of the candidates to be flown on future earth observation satellites. But spaceborne lidar is our first trial and we have some technical issues to resolve before establishing operational sensor. So we start development of the Spaceborne Lidar Experimental Model as a first step of lidar program of NASDA. The Spaceborne Lidar Experimental Model will be launched in early 2001. The purpose of the Spaceborne Lidar Experiment is technological demonstration of system design and critical components to apply to future operational sensor. And we demonstrate availability of lidar observation data and scientific value. There are some critical points to resolve such as (1) thermal design of laser oscillator which remove locally-generated-heat effectively and (2) mirror design with little distortion.

The nonstationary dynamics of the free-electron laser oscillator with a low-Q cavity and a broad feedback frequency bandwidth is studied. A method for accounting for the feedback frequency dispersion within the framework of the spatio-temporal approach is proposed. It is shown that broadband dispersion changes the dynamics of the laser excitation, even when its bandwidth is large compared with the amplification bandwidth. Because of the reduction of the number of competing longitudinal modes, the transient time is significantly shortened. Moreover, the current threshold of stability of the single-frequency generation is considerably enlarged.

We investigate the thresholds of periodic and chaotic oscillations in a free-electron laser oscillator by using self-consistent time-dependent one-dimensional Maxwell-Lorentz equations. We consider a Raman-like case where the space charge effects are pronounced. From the parameter dependence of the limit-cycle oscillation frequency, we modify the previous fitting formulas and specify the regimes for the periodic limit-cycle oscillation and for the chaotic oscillation.

We investigate the spatial characteristics of a Nd:YAG unidirectional ring resonator formed by an adaptive holographic gain-grating. Diffraction-limited spatial output is demonstrated from the resonator even with very strong intracavity phase distortion. We also show that, despite good intracavity phase compensation and good spatial output quality, the output mode size is not generally the same as the self-intersecting input beam that forms the gain hologram. A simplified theory, to account approximately for a spatially-Gaussian input beam, gives qualitative agreement with the key features observed in the experimental resonator.

A cw diode-pumped, compact and efficient Nd:YLF laser producing stable picosecond pulses at 1053 nm has been developed as a source for a multi-terawatt laser.

With one-dimensional Maxwell-Lorentz equations, we have investigated the bifurcations in a short-pulse free-electron laser oscillator. A generic Hopf bifurcations and chaotic transition via period-doubling cascade have been described in the parametric space of three branching parameters: the cavity detuning parameter D , the slippage parameter S , and the superradiant parameter K . The present theory of the period of limit-cycle oscillation in the radiation power is well consistent with recent experimental results.

We report on a diode laser-pumped Q -switched Nd:YLF (yttrium-lithium-fluoride) laser oscillator operating in the pulse- transmission mode (PMT). It produces 1047 nm TEM 00 laser pulses with variable duration of 2.4–8.4 ns and an energy of about 0.1 mJ, corresponding to ∼40 kW of maximum peak power. A 50 W, quasi-cw (pulse duration 400 μs) diode laser bar is used as the pump source in a novel two-sided longitudinal pumping geometry.

The start-oscillation current, gain and energy spread requirement for operation of a Smith-Purcell free-electron laser oscillator are determined. The effects of beam thickness, energy spread and gyromotion on the efficiency are discussed.

Recent results obtained with the Orsay free electron laser are summarized in this paper. The laser oscillator was operated at two different wavelengths (6500 and 5800 A) and at energies ranging from 166 MeV to 224 MeV. The main results presented here concern the Q-switched operation, the macro-temporal structure and the saturation mechanism of the storage ring free electron laser.

In a double laser oscillator operating on the 3s2-2p4 and 2s2-2p4 transitions of neon, the red oscillation was mode-locked. The locking was transferred to the other oscillation via the common level. Two alternative round-trip phases of the circulating light pulses occurred. The in-phase state is ascribed to a Raman-like two-quantum interaction.

A simple model for a laser oscillator has been analysed to determine the single mode efficiency for steady state operation at high pumping levels. The analysis takes into account the possibility of changes in the shape of the electromagnetic mode as the pumping rate is increased. Normalised plots of laser efficiency as a function of pumping rate and laser length indicate that changes in mode shape are important at moderate pump levels.

An iodine laser oscillator is described, which delivers several mJ in ns-pulses. The oscillator is mode-locked by means of an acoustooptical modulator, the pulse duration varies with the iodine pressure. Apparent self-modelocking is due to saturation effects.

A stability criterion for the self-pulsing laser oscillator is derived from the numerical analysis of a mathematical model previously described. A numerical solution for the pulse shape is also presented.

To obtain single transversal mode oscillation of a laser oscillator a pinhole has to be inserted into the resonator. This causes diffraction losses, comparable with the internal losses of the laser system. For a pulsed Nd-YAG-laser, the total losses and the diffraction losses are determined experimentally as a function of the Fresnel number for TEM 00 and TEM 01 mode. The agreement between the experimental values and numerical data from diffraction theory is satisfying.

We present a master equation for amplified spontaneous emission and show the nonlinear saturation effects are dominated by parametric terms which are the analogue of mode-locking terms in laser oscillator theory.

Discharge modulation noise in HeNe laser radiation is considered theoretically, including explicitly the laser oscillator properties. Experiments reported previously by us and other authors are in agreement with our analysis.