Victor E. Semenov

Extremely short dissipative solitons in an active nonlinear medium with quantum dots

A medium consisting of quartz with embedded active (amplifying) or passive (absorbing) impurities, i.e., quantum dots, is proposed for producing extremely short dissipative solitons on the basis of the effect of enhanced self-induced transparency. The calculations show that, in such a medium, the initial standard femtosecond pulses can be transformed into extremely short dissipative solitons with a peak intensity of ∼1011 W/sm2, with a duration corresponding to the inverse frequency of transitions in impurities, and with the coherent spectral supercontinuum covering almost the entire transmission region of quartz.

Experimental and computer investigations of slab waveguide rf-excited CO2 laser

Results of investigations of a slab waveguide rf-excited carbon-dioxide laser are presented. Laser output power of range 200 W and efficiency about 10% in a beam with near-diffraction- limit divergence has been achieved. In the repetitive-rate mode, the pulsed power was more than twice as much as the average one in the cw mode. After beam shaping telescope, the total beam divergence of 2 - 3 mrad at the 0.8 power level has been obtained. A codes package of computer simulation of cw slab rf-excited diffusion-cooled carbon-dioxide laser was created. Comparison of calculated and experimental data has been fulfilled.

Optical Problems of Laser Radiation Transport in the LOTV Concept

In the scope of the LOTV concept optical problems have been considered of a laser power transport from an airborne laser, flying at a 10‐kilometer altitude, to a space “tugboat” with a laser propulsion engine (LPE), intended for payload orbital transfer from LEO to GEO. For a transmitter telescope size of 1–1.5 m the range of optimal sizes of a receiver collector as well as the range of optimal specific impulses of LPE have been determined for the radiation wavelength of 0.5 μ and 1 μ, and payloads of 3–5 t. The optimization was carried out by searching a trade‐off between propellant mass saving and the orbit transfer time reduction.

On a Possibility of Laser Beam Control in LOTV Mission by Means of Nonlinear and Coherent Optics Techniques

In the context of LOTV Mission (Laser Orbital Transfer Vehicle) the analysis of laser beam delivery efficiency has been carried out for power beaming with a 200‐kW‐solid‐state laser from an aircraft to a space “tugboat” having a beam receiving collector of 10‐meter‐size. Application of nonlinear‐optics and adaptive optics techniques of laser beam control for correction of optical distortions in the propagation path caused by vibration and thermal deformation of optical elements as well as by atmospheric turbulence is discussed. Possible architecture of laser beam transport systems including a laser beacon on the receiver, a repetitively pulsed solid‐state laser in MOPA‐PCM configuration and a beam director telescope of 1‐meter size is considered. The results of computer simulation of a MOPA‐PCM system as well as the system as a whole are presented. The requirements to optical elements of the system are discussed.

High-power high-optical-quality rf-excited slab CO2 lasers

For the various pumping rates and for the various heights of the gap were calculated the average value of the small- signal gain and its profile across the gap. For the high power slab CO2-lasers, RF-excited at 40.68 MHz, were analyzed the ranges of their geometry parameters vibration, providing for the possibility of diffraction limited performance. In theory and in experiment was shown the possibility to select the basic waveguide mode of radiation.

Optical needles: ultra-narrow Maxwell's spatial solitons in Kerr media

The limiting levels of light energy concentration can be achieved by shortening of laser pulses (femto- and attosecond range) and by transverse squeezing of beams (sub-micrometer sizes). The latter approach can be realized in media with nonlinearity of refractive index of self-focusing type.

Slab waveguide high-power pulsed rf-excited CO2 laser

Slab RF-excited pulsed CO2-laser with the pumping frequency F equals 152 MHz, pulse duration in the range of 20 divided by 50 microsecond(s) , and pulse repetition rate f up to 100 Hz has been investigated. Output power, temporal shape of laser pulses, laser beam divergence were measured at the pumping power up to 400 W/cm3. Pulsed output power was varied in the range of 2 divided by 5 kW. The package of numerical simulation codes of pulse-repetition mode of slab CO2 laser was created. It is shown that the maximum input power is significantly increased by the change of excitation frequency from 80 up to 150 MHz. The measured and numerical data are compared.

Few cycle dissipative soliton pulses

We find a novel class of stable dissipative solitary waves with discrete velocities and few cycle temporal duration in a composite medium containing active and passive atoms.

New approach to the formation of the basic waveguide radiation mode in a high-power slab-type CO2 laser

The paper presents a new approach for radiation mode formation, based on the proper choice of the discharge electrodes shape and the distance from the resonators mirrors to the butt-end of electrodes. In theory and in experiment was shown the possibility to select the basic waveguide mode of radiation. For 2.5 KW slab CO2 laser, excited at 40,68MHz, was obtained the near diffraction-limited divergence.

Computer Simulation of a Solid‐State Laser System for Propulsion of a Space “Tugboat” from LEO to GEO

Development of Laser Orbital Transfer Vehicles (LOTV) driven by an aircraft‐based laser requires correction for laser beam distortion caused by the aircraft vibration, thermal deformation of laser optics, turbulence and nonlinear effects in upper layers of the atmosphere, etc. We have analyzed a possibility of combined use of an adaptive optics system (AOS) and phase conjugate mirrors (PCM) for the beam clean up and correction for turbulent distortion using a beacon laser at the “tugboat”. The analysis is performed for a repetitively pulsed 200 kW Yb:YAG diode‐pumped solid‐state laser with a 1 meter class beam‐director. The results of computer simulation of the system performance for different distances from 300 to 36000 km are presented.