Margarita Deneva

A novel technique for a narrow line selection and wideband tuning of Ti:Al2O3 and dye lasers

We have developed a novel simple technique for a wide gain laser narrow line selection and tuning using classical interferometric selectors (Fabry–Perot interferometer, interference wedge). Its most important advantage is that selection and tuning need only one thick interferometer instead of a combination of a thin (5 μm) and a thick (∼100 μm) one as in the conventional approach. This makes tuning much simpler without having to synchronize two tuning elements and the system as a whole essentially cheaper. The computer simulation and the experimental test have shown that the proposed technique is highly competitive compared with traditional interferometers with thicknesses of 30–70 μm. It assures a spectral resolution of less than ∼0.01 nm and tuning in the wide region (≥100 nm), in particular, it completely covers the spectrum of the dye solution and that of the Ti:Al2O3 crystal. Besides enlarging the tuning region, the linewidth is narrowed and the spectral purity of emission is increased. Using a quali...

Two-wavelength, passive self-injection-controlled operation of diode-pumped cw Yb-doped crystal lasers

We demonstrate and investigate a peculiar mode of cw Yb3+-doped crystal laser operation when two emissions, at two independently tunable wavelengths, are simultaneously produced. Both emissions are generated from a single pumped volume and take place in either a single beam or spatially separated beams. The laser employs original two-channel cavities that use a passive self-injection-locking (PSIL) control to reduce intracavity loss. The advantages of the application of the PSIL technique and some limitations are shown. The conditions for two-wavelength multimode operation of the cw quasi-three-level diode-pumped Yb3+ lasers and the peculiarity of such an operation are carried out both theoretically and experimentally. The results reported are based on the example of a Yb3+:GGG laser but similar results are also obtained with a Yb3+:YAG laser. The laser operates in the 1023-1033-nm (1030-1040-nm) range with a total output power of 0.4 W. A two-wavelength, single longitudinal mode generation is also obtained.

Tunable subnanosecond pulse generation in a dye laser using overlapped pump pulses

We report a simple technique for generation of tunable subnanosecond pulses (0.2–0.4 ns) based on single spike selection from the relaxation oscillations in a dye laser using preformed and overlapping in time excitation pulses. The pulses were obtained by temporal division of a 5–50 ns initial pulse using a Pockels cell with a 1–2 ns switching time and an optical delay time. The proposed technique widens the choice of suitable dye lasers in which the single spike selection technique may be applied, to include dye lasers excited by a Q-switched solid-state laser or a Cu-vapor laser. Other advantages to this technique are the shortened length of the generated subnanosecond pulse, the increased energetic output, higher reproducibility, and the possibility for synchronization of spike generation to an external signal accurate to within 2–3 ns.

Increase of the free-spectral range by composing a structure from wavelength tunable wedged interferometers

We have studied a structure composed from two wavelength tunable wedged interferometers and proved its potential for providing an increased free spectral range in comparison to a conventional interferential wedge. The interferential wedges with optical thickness from several micrometers to several hundred micrometers and apex angles of the order of tens microradians have been used. We have computed transmission for a monochromatic light beam with arbitrary wavefront using the angular spectrum approach for interferential wedges with different optical thicknesses and apex angles. We have conducted experiments with several stacks formed from different two wedges. Thus, we have confirmed selection of a single transmission resonance within the impact area of a large diameter beam instead of occurrence of multiple transmission peaks observed for a single interferential wedge. The stack enables wavelength tuning for a small diameter multi-wavelength beam in an increased spectral range at keeping high spectral resolution if the structure is formed by a thin and a thick interferential wedges. The experiments have shown that the selected transmission peak is narrowed spatially and spectrally at the expense of lower transmission, which is 50-60% of transmission provided by the used interferential wedges.

DEVELOPMENT OF ORIGINAL OPTICAL AND QUANTUM ELECTRONICS DEVICES FOR APPLICATIONS IN COMMUNICATIONS, METROLOGY AND SCIENCES

The goal of the report is to present the development – principles, theories and computer simulations, experiments and practical realizations, of original and competitive methods, elements and devices for quantum electronics, optical communications, metrology, remote sensing and sciences: multi-channel WDM system with independent tuning of each input/output, multi-wavelength laser with independent control of each wavelength, lasers with emission, spectrally fixed at reference atomic absorption line, injection-locking laser system for high (~10-10) and linear amplification of low-power (~ μW, nW) modulated laser light, optical analogue of the transistor action – optical transistor, system for remote (up to kilometres) measurement of small (mm) translational elongation – shrinking of objects, new solution of tunable sub-nanosecond lasers and lasers with rectangular nanosecond (~1 ns) pulse emission, including controlled duration and tunable wavelength. The basic element of the devices developed is stable and compact interference wedged structures in new composite solution with very narrow transmission (≤ 0.01 nm) in relatively large spectral range (≥1 nm). The laser active media used are solid-state, semiconductor and dye.

Near-maximum-efficiency two-wavelength Ti:Al2O3 laser using a novel combined PSIL-dual-pulse pumping spectral control

We demonstrate how a pulsed two-wavelength tunable Ti:Al2O3 laser can operate at near maximum efficiency, obtained in an optimized non-selective cavity. To achieve this efficiency we solve the intrinsic of the Passive Self- Injection Locking (PSIL) method problem of non-controlled free lasing at high pump level by combining the PSIL control with an appropriate dual-pulse pumping. Laser efficiency is increased and the background emission is limited to less than 1 percent in a region ten times larger compared with the standard PSIL control. From analysis we have found optimum conditions and show the advantages of this combined technique. The proposed approach is compared with spectral control of a Ti:Al2O3 laser, realized by injection from a coupled two-wavelength dye laser.