Valerii V. Ter-Mikirtychev

Tunable LiF:F/sub 2//sup -/ color center laser with an intracavity integrated-optic output coupler

A new LiF:F/sub 2//sup -/ color center laser operation has been achieved by inserting a SiO/sub 2/ thin-film waveguide in the laser cavity. The waveguide was deposited on LiF bulk crystal substrate with a holographic grating. The laser beam from the waveguide was tunable in 1150-1172 nm spectral range. The maximum ratio of the pulse energy of the laser radiation coupled out through the waveguide to that of the pump-radiation was 0.3%. The beam was stretched into the direction perpendicular to the waveguide plane, with a divergency of 7.2/spl times/10/sup -2/.

Characteristics of the LiF:F3+ color center laser

Abstract A LiF:F 3 + color center laser was pumped by the second harmonic beam of a Ti: sapphire laser pumped by YAG:Nd 3+ laser. A limited stability was obtained in the laser operation. We studied the photochemical processes occurring in such pumping and the reason for the limited LiF:F 3 + laser operation.

Tunable visible solid-state lasers based on second-harmonic generation of LiF:F(2) in potassium titanyl phosphate.

A new broadly tunable visible solid-state laser is reported. Wavelengths between 550 and 610 nm are generated by intracavity frequency doubling of tuned and free-running room-temperature pulsed LiF:F(2)(-) lasers in potassium titanyl phosphate. Second-harmonic energy of 1.3 mJ has been achieved, corresponding to a fundamental-to-second-harmonic conversion efficiency of 20%. Operation is optimized with respect to LiF:F(2)(-) laser parameters.

Ultrabroadband LiF:F2+∗ color center laser using two-prism spatially-dispersive resonator

Abstract A room-temperature-stable ultrabroadband nanosecond IR laser oscillation has been obtained using a F 2 +∗ color center in OH − - and Mg 2+ -doped LiF crystals. Multifrequency laser operation has been performed using a “spatially-dispersive” resonator which contains an intracavity cylindrical lens, a prism pair, and a linear diaphragm. The output power spectrum has a 850–1040 nm range. This range is almost comparable to the bandwidth of the F 2 +∗ luminescence spectrum.

Stable, efficient room-temperature LiF:F2+∗ laser, tunable in the 820–1200 nm region, pumped by a YAG:Nd3+ laser with an injection seeded solid-state wavelength convertor

Abstract Room-temperature-tunable, pulsed LiF:F2+∗ color center laser operation has been realized using the 575 nm pumping radiation from a YAG:Nd3+-laser-pumped LiF:F2− oscillator injection seeded by a low power 1150 nm He–Ne laser. The LiF:F2+∗ laser demonstrated stable and tunable operation in the 820–1200 nm region with 26% real efficiency at the maximum of the tuning curve. 50% real efficiency has been achieved for the LiF:F2+∗ laser in a free running operation using a non-selective plane Fabry–Perot optical resonator.

Laser and absorption saturation measurements of Cr4+ crystals, pumped by broadband pulsed 940 nm radiation

Abstract The characteristics of a 940 nm pumped Cr 4+ :forsterite laser have been investigated using a pulsed colour centre laser as the excitation source. Laser threshold, slope efficiency and temporal behaviour have been determined for high and low Cr 4+ doped material. 940 nm pumping is found to be more efficient than 532 and 730–770 nm excitation. Discrepancies with 1064 nm pumping are attributed to excited state absorption. Absorption saturation measurements have been used to assess the potential applications of Cr 4+ :forsterite, Cr 4+ :YAG and Cr 4+ : Lu 3 A1 5 O 12 (LuAG) as passive Q-switches for Nd lasers in the 940 nm region.

Tunable yellow–green laser based on second harmonic generation of LiF:F−2 in KTP

A yellow–green solid-state laser source based on frequency- doubling of a room temperature LiF:F−2 laser in KTP is reported. Second harmonic generation of free-running and prism-tuned pulsed lasers has been characterized. Tunable operation between 555 and 595nm was obtained, with a conversion efficiency of 7.5% for the free-running laser, and up to 4% for the prism-tuned configuration. The angular bandwidth of 60milliradians exceeded the theoretical value by a factor of 3.5. A flattened tuning curve in the visible region was obtained through enhanced conversion efficiency in the wings of the LiF:F−2 laser tuning range.

Diode-pumped LiF:F/sub 2//sup +*/ color center laser tunable in 880-995-nm region at room temperature

Pulsed operation of a tunable LiF:F/sub 2//sup +*/ color center laser has been obtained at room temperature under pumping by 680-nm fiber-coupled linear array laser diodes for the first time to the authors knowledge. The LiF:F/sub 2//sup +*/ tunable laser operates in 880-995-nm region by use of an intracavity birefringent plate. Using a nonselective resonator the laser showed 3% pumping-to-lasing conversion efficiency. In the tunable narrow band operation the measured optical-to-optical conversion efficiency was 2%. The obtained result is expected to cause more widespread applications of diode-pumped LiF:F/sub 2//sup +*/ laser and possibly its commercialization.

Improving the beam quality of solid-state systems using both outside and inside cavity devices with variable optical characteristics along the cross section

This paper presents the results of application to different laser installations of soft or apodized apertures (AA) [1–3] with smooth transmission profiles decreasing from center to edges. Two types of AA, which were made of CaF2:Pr crystals, have been used: induced absorption (IA) AA and photooxidation (PhO) AA. The ∼3–45-mm-diameter IA and PhO AA with smooth monotonic flat-top profiles have been used in 1.06-μm laser amplifier systems to suppress hard-edge Fresnel diffraction rings in beam cross section and to increase the second harmonic conversion efficiency. The ∼3–4-mm-diameter PhO AA with bell-like transmission profiles were placed inside the 2.94-μm and 1.06-μm resonators of master oscillators. The tendency of the output energy to increase by 1.3–1.8 times and the decrease in beam divergence in single-mode lasing as compared with a hard-edge aperture have been observed in the experiments described below.

Broadly-tunable high-power fiber laser system for IR spectral range

Broadly tunable fiber laser system has been demonstrated at room temperature. The IR fiber laser system consists of two high peak power individual pulse fiber lasers and their difference frequency generation (DFG) in Periodically Poled Lithium Niobate (PPLN) nonlinear optical crystal. Both lasers were operating at 20 kHz Pulse Repetition Rate and 200 ns pulse duration with diffraction limited beam quality. The first laser is a CW, < 16 GHz spectral bandwidth, tunable in 1050-1081 nm spectral range and Acousto- Optically extra cavity amplitude modulated Yb fiber laser ring oscillator - high power two stage amplifier which produced 280 mW of average and 70W of Peak power, respectively. The second laser is a DFB CW, single 1556 nm wavelength, < 1MHz spectral bandwidth and extra cavity amplitude modulated Er fiber laser oscillator - high power single stage amplifier with 160 mW of output average power and 40W of peak power. Synchronized pulses from two fiber lasers have been combined and fiber coupled into a single polarization maintained fiber using a fiber WDM combiner and then fibercoupled into the NovaWave Technologies, commercial DFG laser module which employed 50 mm PPLN crystal. The DFG stage of the system produced tunable radiation in 3236.4-3545.4 nm spectral range (309 nm). The difference frequency generation has a 9 mW average power, 20 kHz pulse repetition rate and 200 ns pulse duration which corresponds to 2.25 W of peak power. The demonstrated pulse DFG conversion efficiency is 0.2 W/W2 (20%/W) which is ~ 100 times higher than that of CW operation. Further scaling of IR laser power was limited by optical damage of PPLN crystal and fiber lasers combining optics. Using a PPLN-MgO crystal and additional fiber laser amplifier stages based on Large Mode Area gain fibers is expected to allow us to achieve damage free difference frequency generation with up-to 100 mW of average power and peak power of up to 25 W.