A Diode-laser-bar Pumped Stable CW Nd: YAG Slab Laser and its Frequency Doubling

Abstract

A high power Nd: YAG mini-slab laser transversely pumped by two diode laser arrays has been investigated. The simplicity and compactness of this pumping scheme provides intrinsic stability in both the output power and the beam pointing. A linearly polarized TEM₀₀ mode output power of 3·6 W at 1064 nm was achieved with a linear cavity, and 1 W of single frequency green light at 532 nm was generated by intracavity doubling in a ring cavity.     

Theory of a Free-electron Laser Amplifier

Abstract

The amplification of the free-electron laser is discussed in terms of the effective number of electrons whose scattered radiations are in phase with the stimulating laser wave. The gain of amplification is calculated in terms of the scattered radiation power emitted by a single electron and it is proportional to the cube of the electron total energy. The Stanford experimental measurements of the gain as a function of the electron energy and laser power are used to test the new gain formula with good agreement.     

Pulsed difference frequency generation regime in dual-wavelength vertical-external-cavity surface-emitting laser

The parameters of middle-IR radiation (λ ∼ 17 μm) generated as a result of the intracavity nonlinear optical interaction in a semiconductor dual-wavelength vertical-external-cavity surface emitting laser operating in a pulsed regime have been numerically analyzed. The dependence of the peak output radiation power on the length of the nonlinear crystal has been studied for various values of the loss factor.     

Laser multipass probing in Thomson plasma diagnostics

A new approach to a system of laser probing for Thomson diagnostics of a high-temperature plasma is proposed. The approach is based on the principles of multipass intracavity laser probing, which can improve the sensitivity of the method by between one and two orders of magnitude and allows the electron temperature to be measured at frequencies higher than 10 kHz. Results of testing a probing system developed for the FT-2 tokamak are presented. Pis’ma Zh. Tekh. Fiz. 23, 65–72 (April 26, 1997)     

Possible emission of supermodes in a free electron laser with a transversely developed interaction space

A theoretical analysis is made of the formation of the transverse field profile in a free electron laser with an oversize planar-geometry Bragg cavity driven by a ribbon electron beam. It is shown that cw spatially coherent lasing may be achieved with an oversize parameter of the order of 50 with the excitation of supermodes comprising a set of “ cold” waveguide modes. Pis’ma Zh. Tekh. Fiz. 25, 28–34 (March 12, 1999)     

Decoherence slowing via feedback

Abstract

It is shown that the decoherence of the Yurke–Stoler coherent state of a field in an open cavity can be significantly slowed down when the feedback is organized between the outgoing radiation and the intracavity field.     

Ti:Al2O3 laser pumped by radiation from a copper-vapor laser

A scheme enabling spatial matching of copper-vapor laser radiation, which pumps a mode of an Al₂O₃:Ti laser cavity, has been developed and implemented. It is shown that copper vapor lasers as pump sources for titanium-sapphire lasers are fully capable of competing with conventional pump sources. Pis’ma Zh. Tekh. Fiz. 25, 6–11 (September 26, 1999)     

Doubled single-frequency Nd:YLF ring laser coupled to a passive nonresonant cavity

We demonstrate an original solution to obtain a single-frequency ring laser coupled to an external passive nonresonant ring cavity, which plays the role of an optical diode. This system provides more output power than systems with an intracavity unidirectional device. To the best of our knowledge, this work marks the first demonstration of a unidirectional planar ring laser at 1.3 microm. Using 12 W at 797 nm to pump a Nd:YLF laser, combined with intracavity second-harmonic generation, we achieve yields of 440 mW at 661.3 nm and 340 mW at 656.0 nm.     

Lasing characteristics of lasers with a vertical cavity based on In0.2Ga0.8As quantum wells

Semiconductor lasers with a vertical cavity with a high external quantum efficiency and high radiation power have been developed and constructed. Powers up to 10 W at T=300 K and 20 W at T=250 K have been obtained for 500 μm aperture lasers operating in the pulsed regime. Pis’ma Zh. Tekh. Fiz. 25, 40–44 (October 12, 1999)     

Four watt long-term stable intracavity frequency-doubling Nd:YVO(4) laser of single-frequency operation pumped by a fiber-coupled laser diode

The longitudinal-mode stability of a single-frequency intracavity frequency-doubling laser can be enhanced by increasing the ratio between the nonlinear spectral bandwidth and the gain bandwidth of the laser. A 4 W long-term stable cw single-frequency green laser is obtained using an etalon inside the laser cavity as a spectral filter. No mode hopping is observed when the laser operates for 6 h and the power fluctuation is less than +/-1.2%. In contrast, in the situation of no etalon inside the laser cavity, mode hopping can be observed at irregular intervals and the power fluctuation is +/-3.8% when the laser operates for 4 h.     

High-power and high-quality, green-beam generation by employing a thermally near-unstable resonator design

We have obtained green-beam quality of M2 = 6.2 at an average output power of 120 W by intracavity frequency doubling of a diode-side-pumped, Q-switched Nd:YAG rod laser with a repetition rate of 10 kHz and an optical-to-optical conversion efficiency of 15.2%. To achieve high-beam quality at high average power, the laser employs a thermally near-unstable resonator design with two-rod birefringence compensation in an L-shaped flat-flat cavity. The output power fluctuation of the green laser remains less than 0.9% in 4 h.     

Pair production in counterpropagating electron and laser beams

An analysis is made of the collision between a high-energy electron beam and laser radiation. It is shown that when the electron energy is 800 GeV and the laser pulse has an intensity of 10²⁰ W/cm², a wavelength of 248 nm, and a duration of 300 fs, a single seed electron produces 60 electrons and positrons. Pis’ma Zh. Tekh. Fiz. 23, 72–75 (July 26, 1997)     

Stable 4 W CW solid-state green source pumped by fibre-coupled diode-laser arrays

Abstract

A high-power Nd:YAG laser end-pumped by a fibre-coupled diode-laser array system is described. When operated at 1 μm, the device produced 10 W of output power in the TEM₀₀ transverse mode with a slope efficiency of 43%. The system was operated using both 600 μm and 400 μm core, 0·37 N.A. multimode fibres for delivery of the pump radiation, and also with Nd:YVO₄ as the gain material. By intracavity doubling with KTP, 4 W of non-chaotic two-mode 0·5 μm output was obtained.     

Some laws governing laser beam ignition of an ethylene stream in air

The process of laser beam ignition of an ethylene stream in air has been studied experimentally. It has been established that the ignition process has two stages and the threshold power of the igniting laser radiation is extremely low. Pis’ma Zh. Tekh. Fiz. 23, 46–50 (December 26, 1997)     

Efficient Operation of an Intracavity-Doubled Nd:YVO(4)/KTP Laser End Pumped by a High-Brightness Laser Diode

Using a 1-W high-brightness laser diode as the pump source, we investigated the output characteristics of an intracavity frequency-doubled Nd:YVO(4)/KTP laser. Highly efficient operation was realized based on an optimized cavity design. The second-harmonic output power at 532 nm was measured to be 286.5 mW at an incident pump power of 881.4 mW, corresponding to an optical-to-optical efficiency of 32.5%.     

Electron dynamics during laser neutralization of negative ions

A hydrodynamic approach is used to study the electron dynamics when laser radiation acts on a negative ion beam. An analytic solution of the problem is obtained. Pis’ma Zh. Tekh. Fiz. 24, 38–42 (May 12, 1998)     

Spectrum of a Micromaser with Kerr Nonlinearity

Abstract

We analyse the spectrum of a micromaser with a Kerr-type nonlinearity in its cavity. We show that the intracavity Kerr nonlinearity has significant effects on the spectrum leading to narrowing of the subnatural linewidth and frequency-shifts.     

Modulation of the polarization of semiconductor laser radiation at constant output power

The degree of polarization of “doubly”-modulated (by the pump current and the optical confinement factor) laser radiation is analyzed by applying a method of analyzing the stability of the solutions of systems of Lyapunov differential equations to a system of rate equations. An analysis of the system of rate equations yielded its eigenvalues, also called stability coefficients, which are the characteristic time for a transition of the system from one state to another. The behavior of a doubly modulated laser was modeled mathematically and it was demonstrated that the polarization of the laser output radiation can be controlled with almost constant output power. Pis’ma Zh. Tekh. Fiz. 24, 84–90 (August 26, 1998)     

A History of the Photographic Lens

Abstract

We investigate the transient and the steady-state behaviour of the photon statistics of a single-atom laser, consisting of a three-level Λ system, driven by an incoherent external pump field and strongly coupled to a single mode of an optical cavity. For several limiting cases we are able to obtain analytical results. A comparison with standard multi-atom laser theory reveals a surprisingly good agreement down to very small intracavity photon numbers. Under appropriate operating conditions a calculation of the second-order intensity correlation function yields sub-Poissonian statistics as well as strong antibunching induced by the nonlinear dynamics of the atom.     

Q-switching in single-heterojunction lasers and generation of ultrahigh-power picosecond optical pulses

Q-switching has been obtained for single-heterojunction lasers. The ultrafast saturable absorber in the laser cavity is created by implantation of high-energy heavy ions. The peak power generated by the lasers in a 150 μm stripe width is 380 W with a pulse length of 40 ps. Pis’ma Zh. Tekh. Fiz. 23, 11–16 (February 26, 1997)