Aleksandr V Konyashchenko

177fs erbium-doped fiber laser mode locked with a cellulose polymer film containing single-wall carbon nanotubes

A mode-locked soliton erbium-doped fiber laser generating 177fs pulses is demonstrated. The laser pumped by a 85mW, 980nm laser diode emits 7mW at 1.56μm at a pulse repetition rate of 50MHz. Passive mode locking is achieved with a saturable absorber made of a high-optical quality film based on cellulose derivative with dispersed carbon single-wall nanotubes. The film is prepared with the original technique by using carbon nanotubes synthesized by the arc-discharge method.

Femtosecond Er3+ Fiber Laser for Application in an Optical Clock

The main elements needed for the realization of a compact femtosecond methane optical clock are developed and studied. A femtosecond laser system on an Er3+ fiber (λ = 1.55 μm) contains an oscillator, an amplifier, and a fiber with a relatively high nonlinearity in which the supercontinuum radiation is generated in the range 1–2 μm. In the supercontinuum spectrum, the fragments separated by an interval that is close to the methane-optical reference frequency (λ = 3.39 μm) exhibit an increase in intensity. The supercontinuum radiation is converted into the difference frequency in a nonlinear crystal to the range of the methane-reference frequency (λ = 3.3–3.5 μm), so that the frequency components of the transformed spectrum have sufficient intensities for the subsequent frequency-phase stabilization with respect to the methane reference. A system that stabilizes the pulse repetition rate of the femtosecond Er3+ laser is also employed. Thus, the repetition rate of the ultrashort pulses of the femtosecond fiber laser is locked to the methane reference. The pulse repetition rate is compared with the standard second. Thus, the scheme of an optical clock is realized.

Methane based microwave reference oscillator

Two microwave reference oscillators based on a He-Ne/CH<inf>4</inf> optical frequency standard (λ = 3.39 μm) and femtosecond Er fiber laser (λ = 1.55 μm) optical-to-microwave frequency divider were created. The measurements have demonstrated short term frequency instability (Allan deviation) of the output microwave signal at 1.5 GHz at the level of 1×10⁻¹⁴ (τ = 1 s). Interrogative oscillator with such stability is attractive for application in Cs and Rb atomic fountains.

Femtosecond compressed-nitrogen Raman laser

We have estimated the minimum laser pulse duration at which stimulated Raman scattering in gases is possible. Femtosecond Ti : sapphire laser pulses have been converted to the first Stokes in compressed nitrogen using double-pulse pumping of a gas-filled capillary tube by orthogonally polarised chirped pulses. We have obtained 980-nm Stokes pulses of 51 fs duration. The energy conversion efficiency was 12 % at a pulse repetition rate of 1 kHz and average laser output power of 2 W.

Temporal compression of pulses from a 100-KHz-repetiton-rate femtosecond ytterbium laser

We report the temporal compression a femtosecond ytterbium laser pulse at a pulse repetition rate of 100 kHz using the effect of nonlinear self-phase modulation in a gas-filled capillary. A 260-fs laser pulse is compressed down to 17 fs with an energy efficiency of 40%. An average radiation power at the compressor output is 2 W. At a second compression stage, the time contrast is increased and the pulse duration is reduced in the process of the second harmonic generation in a KDP crystal. The obtained pulses have a duration of 11 fs at an efficiency of 35%.

1-kHz-repetition-rate femtosecond Raman laser

A femtosecond Raman laser utilising compressed hydrogen is experimentally investigated under pumping by radiation from a 1-kHz-repetition-rate Ti : sapphire laser. In the regime of double-pulse pumping, the conditions are determined, which correspond to the minimal energy dispersion of Stokes pulses. The optical scheme is realised, which is capable of ensuring the long-term stability of the average power of the first Stokes component with a variation of less than 2%. The Stokes pulses are produced with a pulse duration of 60 fs and energy of 0.26 mJ at a conversion efficiency of 14%.

Note: 15-fs, 15-μJ green pulses from two-stage temporal compressor of ytterbium laser pulses.

15-fs, 15-μJ light pulses at the central wavelength of 515 nm were generated by two-stage nonlinear compression of 300-fs, 150-μJ ytterbium laser pulses. The compression was based on the pulse spectrum broadening by self-phase modulation in gas filled capillary and second harmonic generation in crystal.