ABSTRACT
A single-layer graphene saturable absorber is employed for passive Q-switching of an Er, Yb:GdAl3(BO3)4 (Er,Yb:GdAB) compact laser, representing the first Er-doped oxoborate laser Q-switched by graphene. This laser is based on a c-cut 1.8 at. % Er3+, 15 at. % Yb3+:GdAB crystal diode-pumped at 0.976 µm. It generates a maximum average output power of 360 mW at 1.55 µm with a slope efficiency of 23% (with respect to the incident power). Stable â¼1 µJ/130 ns pulses are achieved at a repetition rate of 400 kHz. This result represents, to the best of our knowledge, the shortest pulse duration ever achieved in bulk Er lasers Q-switched by 2D materials. Graphene is a promising material for generating nanosecond pulses at high repetition rates (MHz range) in Er-doped oxoborate lasers emitting in the eye-safe range at 1.5-1.7 µm.
ABSTRACT
An investigation of Tm-Ho energy transfer in Tm(5at.%),Ho(0.4at.%):KYW single crystal by two independent techiques was performed. Based on fluorescence dynamics measurements, energy transfer parameters P71 and P28 for direct (TmâHo) and back (HoâTm) transfers, respectively, as well as equilibrium constant Θ were evaluated. The obtained results were supported by calculation of microscopic interaction parameters according to the Förster-Dexter theory for a dipole-dipole interaction. Diode-pumped continuous-wave operation of Tm,Ho:KYW microchip laser was demonstrated, for the first time to our knowledge. Maximum output power of 77 mW at 2070 nm was achieved at the fundamental TEM00 mode.
ABSTRACT
The results of an experimental study of the chirped pulse amplification regime are reported for the Yb:CaYAlO4 crystal with different polarization states in the gain media for the first time, to the best of our knowledge. A maximum output power of 4.2 W with 310 fs pulse duration was obtained for σ-polarization at 200 kHz repetition rate seeded by a 85 fs Yb:KYW oscillator. 215 fs pulses with an output power of 3 W and 190 fs with 2.3 W output power were demonstrated for π-polarized light in the crystal. Gain narrowing effects for different polarization states in the crystal are discussed.
ABSTRACT
A chirped-pulse regenerative amplifier based on a Yb:YVO4 (Yb:YVO) crystal was demonstrated for the first time, to our knowledge. A novel wavelength-independent off-axis technique was used to deliver 26.6 W of pump power with a low quantum defect. It was seeded by means of a 120 fs Yb:YVO4 oscillator. It generates as much as 5.5 W of average output power with chirped pulses and 4.2 W with 200 fs compressed pulses at a 200 kHz repetition rate. A maximum pulse energy of 140 µJ was obtained at pulse repetition frequencies up to 25 kHz at the central wavelength of 1018 nm.
Subject(s)
Amplifiers, Electronic , Vanadates/chemistry , Vanadium Compounds/chemistry , Ytterbium/chemistry , Yttrium/chemistry , Equipment Design , Lasers, Solid-State , Oxides/chemistry , Spectrum AnalysisABSTRACT
We report on a continuous-wave Ho:KLu(WO4)2 (KLuW) microchip laser with a record slope efficiency of 84%, the highest value among the holmium inband-pumped lasers, delivering 201 mW output power at 2105 nm. The Ho laser operating at room temperature on the (5)I8â(5)I7 transition is in-band-pumped by a diode-pumped Tm:KLuW microchip laser at 1946 nm. Ho:KLuW laser operation at 2061 and 2079 nm is also demonstrated with a maximum slope efficiency of 79%. The microchip laser generates an almost diffraction-limited output beam with a Gaussian profile and a M2<1.1. The laser performance of the Ng-cut Ho:KLuW crystal is very similar for pump light polarizations âNm and Np. The positive thermal lens plays a key role in the laser mode stabilization and proper mode-matching. The latter, together with the low quantum defect under in-band-pumping (â¼0.08), is responsible for the extraordinary high slope efficiency.
ABSTRACT
A microchip laser is realized on the basis of a monoclinic Tm,Ho-codoped KLu(WO4)2crystal cut for light propagation along the Ng optical indicatrix axis. This crystal cut provides positive thermal lens with extremely weak astigmatism, S/M = 4%. High sensitivity factors, M = dD/dP(abs), of 24.9 and 24.1 m(-1)/W for the mg- and pg- tangential planes are calculated with respect to the absorbed pump power. Such thermo-optic behavior is responsible for mode stabilization in the plano-plano microchip laser cavity, as well as the demonstrated perfect circular beam profile (M(2) < 1.1). Maximum continuous-wave output power of 450 mW is obtained with a slope efficiency of 31%. A set of output couplers is employed to achieve lasing in the spectral range of 2060-2096 nm. The increase of output coupler transmission results in deterioration of the laser performance attributed to the increased up-conversion losses.
Subject(s)
Lasers, Solid-State , Light , Optics and Photonics/instrumentation , Equipment DesignABSTRACT
A diode-pumped microchip laser containing a quasi-monolithic plano-plano cavity is realized on the basis of a Tm:KLu(WO4)2 crystal. The maximum CW output power is 3.2 W (at an absorbed pump power of 6.8 W) and the slope efficiency as high as 50.4%. The laser is operating at 1946 nm in the TEM00 mode with a M²<1.05. Microchip operation with Tm:KLu(WO4)2 is, in principle, due to a special crystal cut along the N(g) optical indicatrix axis. This crystal cut possesses positive near-spherical thermal lens that provides the required mode stabilization in the plano-plano cavity. Sensitivity factors of the thermal lens, "generalized" thermo-optic coefficients and constants describing the photoelastic effect are determined for the monolithic Tm:KLu(WO4)2 crystal.
ABSTRACT
A detailed experimental study of dispersion and anisotropy of thermo-optic coefficients dn/dT and thermal coefficients of the optical path W=dn/dT+(n-1)α is performed for tetragonal YVO(4) and GdVO(4) laser host crystals by a laser beam deviation method. It is supported by theoretical description of thermo-optic effects, taking into account the volumetric thermal expansion effect and the temperature dependence of electronic bandgap E(g). Linear thermal expansion coefficients α were also determined by a dilatometric technique. Thermo-optic dispersion formulas describing temperature variation of the refractive index and the thermal lens effect are derived for a wide spectral range of 0.4-2 µm. It allows us to estimate the values of E(g) and dE(g)/dT for the studied crystals. The influence of materials parameters and pumping conditions on thermal lens properties is discussed, revealing the significant impact of anisotropic and temperature-dependent thermal conductivity.
ABSTRACT
Thermo-optic coefficients anisotropy was characterized in monoclinic potassium (rare-earth) double tungstates KGd(WO4)2 and KY(WO4)2 in the spectral range of 0.44-0.63 µm by a modified minimum deviation method. This approach takes into account the changes in the shape and dimensions of the prismatic sample caused by the anisotropic thermal expansion effect under uniform heating together with the conventional measurements of minimum deviation angle. At room temperature at the wavelength of 633 nm, principal refractive indices for KGdW are n(p)=2.0135, n(m)=2.0458, and n(g)=2.0860, and for KYW they are n(p)=1.9979, n(m)=2.0396, and n(g)=2.0869. Optical axes position for KGdW (KYW) crystals is N(g) ± 42.60 (N(g) ± 44.1°) in the N(p)-N(g) plane. For both crystals, all the thermo-optic coefficients are negative and equal dn(p)/dT=-10.6, dn(m)/dT=-8.4, and dn(g)/dT=-15.2 for KGdW, and dn(p)/dT=-10.1, dn(m)/dT=-7.3, and dn(g)/dT=-8.4 for KYW [10(-6) K(-1)] (at 633 nm).
ABSTRACT
We measured the thermo-optic coefficients dn/dT of anisotropic Nd:KGd(WO(4))(2) crystals at the wavelengths of 1.064 µm and 532 nm (300 K) by a beam deflection method. The values of dn/dT are determined to be dn(p)/dT = -16.0 × 10(-6) K(-1), dn(m)/dT = -11.8 × 10(-6) K(-1), and dn(g)/dT = -19.5 × 10(-6) K(-1) (at 1.064 µm) and dn(p)/dT = -14.3 × 10(-6) K(-1), dn(m)/dT = -10.0 × 10(-6) K(-1), and dn(g)/dT = -15.0 × 10(-6) K(-1) (at 532 nm). Thermal lensing in the flashlamp-pumped N(p)- and N(g)-cut Nd:KGd(WO(4))(2) laser rods was studied at 1.064 µm by a probe beam technique in the nonlasing conditions, and the contribution of the photoelastic term to the thermal lens optical power was estimated. Athermal propagation directions with the definitions dn/dT + (n-1)α(T) = 0 and dn/dT + nα(T) = 0 were found in Nd:KGd(WO(4))(2).
