Room-temperature CW Laser Operation Research Articles

Continuous-wave laser operation of disordered double tungstate and molybdate crystals doped with ytterbium

Several ytterbium doped disordered doubles tungstate and molybdate crystals, NaGd(WO4)2, NaLa(WO4)2, NaLa(MoO4)2 and LiGd(MoO4)2, were grown with sufficient Yb-doping and optical quality. The crystal field splitting of the Yb3+ multiplets and the lifetimes are similar to the biaxial monoclinic double tungstates but the peak absorption cross sections are roughly one order of magnitude lower. Room temperature cw laser operation was achieved under Ti:sapphire and diode laser pumping. The polarization dependence of the laser emission and possible power scaling were studied. The slope efficiency achieved with the best sample, Yb:LiGd(MoO4)2, was 64.5%. The maximum output power obtained was 900mW for Yb:NaLa(MoO4)2 pumped in the absorption maximum. The laser tunability was studied with an intracavity Lyot filter and the tuning ranges (FWHM up to 33nm) achieved indicate interesting potential for mode-locked femtosecond operation.

Spectroscopy and cw operation of a 1.85 μm Tm:KY3F10 laser

Room-temperature cw laser operation on the 3F4?3H6 transition at 1.85 μm of Tm3+ ions in a KY3F10 single crystal is reported here for the first time. Using a cw Ti:sapphire laser as a pump source, a threshold absorbed pump power of 120 mW and a laser slope efficiency of 42.5% were achieved by using a 45% transmissive output coupler. Optimization of the activator concentration and crystal length is discussed taking into account self-quenching and pump-absorption efficiencies as well as parasitic and intrinsic reabsorption losses. The emission cross-section at the laser wavelength is determined using different methods, showing that the result of the J–O approach is, in this case, very uncertain.

Room temperature CW fibre laser at 3.22 [micro sign

A new fibre laser emission wavelength >3 /spl mu/m is reported. For the first time a Ho/sup 3+/ doped fluorozirconate fibre pumped at 532 nm shows room temperature CW laser operation /spl sim/3.22 /spl mu/m, with output power =11 mW and slope efficiency =2.8%. Fluorescence was observed between 3.12 and 3.41 /spl mu/m.

Room-temperature CW laser operation at ∼1.55 μm (eye-safe range) of Yb:Er and Yb:Er:Ce:Ca/sub 2/Al/sub 2/SiO/sub 7/ crystals

Room-temperature CW laser operation at 1.55 /spl mu/m of Yb:Er:Ca/sub 2/Al/sub 2/SiO/sub 7/ (CAS) single crystal pumped at 940 nm and 975 nm has been achieved for the first time. Introduction of a third doping ion, Ce/sup 3+/, decreases the Er/sup 3+4/I/sub 11/2/ excited-state lifetime and improves the laser properties. For Yb:Er:Ce:CAS single crystal, a maximum of 20 mW output power is produced for 285 mW absorbed power. With this material, a low threshold of 20 mW and a relatively high slope efficiency of /spl sim/5.5% are obtained. Preliminary results indicate possible improvement in the near future. Experimental threshold values and laser properties of CAS crystals with various compositions are in good agreement with calculations, performed using the rate-equations modeling. Comparison with a Yb:Er:phosphate glass laser is also presented.

CW tunable ytterbium YAG laser pumped by titanium sapphire

Room-temperature CW laser operation from Yb/sup 3+/ in YAG is reported. The pump source is a 1 W titanium-sapphire laser tuned to 940 nm. The ytterbium laser was tuned continuously from 1.016 to 1.095 mu m. Output power up to 400 mW was measured with 1 W of pump power incident on the laser crystal.

Efficient 2.05 μm room temperature Y 2SiO 5:Tm 3+ cw laser

Efficient 2.05 μm room temperature cw laser operation of a Tm 3+ -doped Y 2SiO 5 single crystal has been demonstrated for the first time. This system is characterized by a large absorption cross section at about 800 nm and a large stimulated emission cross section around 2 μm with the possibility of a broad wavelength tunability. A slope efficiency of 18% has been obtained under non-optimized conditions.

Cw room-temperature operation of GaAlAs single quantum well visible (7300 Å) diode lasers at 100 mW

100-mW room-temperature cw laser operation at 7300 Å has been achieved in a Ga1−xAlxAs (x∼0.22), ∼300 Å thick, single quantum well double heterostructure diode grown by organometallic vapor phase epitaxy. The proton-delineated stripe contact is 6 μm wide, and the front and rear laser facets are coated for antireflection and high reflection respectively. The cw threshold current is 86 mA for a 250-μm-long device, and linear output power versus current characteristics are observed up to 100 mW with an external differential quantum efficiency of 1 W/A (59%). cw output power exceeds 13 mW at 100 °C. Between 25–55 °C, the pulsed threshold current varies exponentially with temperature T as exp(T/T0), where T0∼187 K.

CW room-temperature visible single quantum well Ga0.73Al0.27As diode lasers grown by metalorganic chemical vapour deposition

Room-temperature CW laser operation at 7125 Å has been achieved in a (Ga1−xAlxAs, x̃0.27) single quantum well double heterostructure (SQW-DH) diode laser. The laser consists of a 9 μm-wide delineated shallow proton stripe. The pulsed threshold current for a 250 μm long device is 115 mA whereas the CW threshold current is 140 mA. The CW external differential quantum efficiency is 60%.

Cw room-temperature InxGa1−xAs/InyGa1−yP 1.06-μm lasers

Room-temperature cw laser operation at wavelengths between 1.06 and 1.12 μm has been obtained from double-heterojunction structures of InxGa1−xAs/InyGa1−yP prepared by vapor-phase epitaxy. These devices have pulsed threshold current densities as low as 1000 A/cm2 and external differential quantum efficiencies as high as 55%. Their active laser cavities are between 0.14 and 0.36 μm thick, providing fundamental transverse-mode operation with far-field patterns 50 to 60° wide.

Optically Pumped Volume-Excited cw Room-Temperature In1−x Gax P (x ≤ 0.60) Platelet Lasers

Room-temperature cw laser operation well into the visible spectrum (λ ∼ 6000 Å) is reported for In1−xGaxP (x ≤ 0.60). Thin (1–5-μ) experimental samples are compressed into In, under a thick (∼ 250-μ) high-index (η > 2. 6) SiC window, with a thin (10–50-μ) narrow SiC platelet under part of the In1−xGaxP sample. The thin In1−xGaxP samples, in the compound cavity, are volume excited in a small spot with an argon laser so that the heat is easily removed by the SiC windows and nearby In heat sink.