Room-temperature Laser Action Research Articles

Continuous wave 1.6 ?m laser action in Er doped garnets at room temperature?

We report on room-temperature cw laser action of Er3+: Yttrium-aluminum-garnet (YAG) and Er3+: Yttrium-gallium-garnet (YGG) crystals at 1.64 μm. The laser operates from the metastable4I13/2 manifold into an upper Stark level of the4I15/2 ground-state manifold of Er3+. Due to reabsorption losses, the Er3+ concentration of the laser crystals must be low. Laser pumping at a wavelength of 647.1 nm yields lowest thresholds around 30 mW and slope efficiencies up to 12.7% for Er:YAG. Laser operation in Er:YGG is achieved with higher thresholds of about 200 mW and smaller slope efficiencies of 0.9%. The effective emission cross section in YAG is estimated to be σe≈5×10−21 cm2.

Continuous-wave laser operation of chromium-doped forsterite

Room-temperature continuous-wave laser action in chromium-activated forsterite (Cr:Mg(2)SiO(4)) has been achieved for longitudinal pumping in a nearly concentric cavity by the 1064-nm radiation from a cw Nd:YAG laser. The laser emission is centered at 1244 nm and has a spectral bandwidth of 12 nm. An output-power slope efficiency of 6.8% is measured. The effective emission cross section is estimated to be ~1.1 x 10(-19) cm(2).

Laser action in chromium-activated forsterite for near-infrared excitation: Is Cr4+ the lasing ion?

Room-temperature pulsed laser action has been obtained in chromium-activated forsterite (Cr:Mg2SiO4) for excitation of the near-infrared absorption band of the system by the 1064 nm radiation from a Nd:YAG laser. The characteristics of laser emission are similar to those observed for 532 nm pumping. It is suggested that the laser action is due to a ‘‘center’’ other than the trivalent chromium (Cr3+), presumably the tetravalent chromium (Cr4+).

Optical properties and lasing of BaLaGa 3O 7 single crystals doped with neodymium

Large single crystals of BaLaGa 3O 7 containing Nd were prepared by the Czochralski method and studied experimentally by absorption and emission spectroscopy. The dependence of the spectroscopic properties of the crystals on temperature, Nd concentration and light polarization was determined. Room temperature laser action associated with the 4F 3 2 − 4I 11 2 transition of Nd 3+ was achieved.

Tunable room-temperature cw laser action in Cr 3+: GdScAl-garnet

We report, for the first time, cw room temperature laser action of Cr 3+:Gd 3Sc 2Al 3O 12. These crystals show a strong band fluorescence due to the 4 T 2 → 4 A 2 transition with a lifetime of 150 μs. Laser pumping in the blue and red spectral range yields a minimum threshold of 170 mW and slope efficiencies up to 18.5%. The emission of the free running laser is centered at 784 nm with a FWHW of 5 nm. The extension of the Ga-garnets to Al-garnets as suitable host lattices for Cr 3+ reveals the variety of garnet-structured crystals having an appropriate ligand field for continuously tunable laser operation.

Laser cathode ray tube with a semiconductor double-heterostructure screen

Room-temperature laser action has been achieved in a cathode ray tube (CRT) in which the target screen is a (GaAs) (GaAlAs) double-heterostructure (DH) single-crystal semiconductor. The light-beam direction is normal to the face of the tube, i.e., parallel to the pump-electron-beam direction and, hence, scannable in two dimensions. Electron-beam energy is 34 keV and threshold current is 700 µA, corresponding to a current density of about 5 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .

Optically pumped 1.55-μm double heterostructure GaxAlyIn1−x−yAs/AluIn1−uAs lasers grown by molecular beam epitaxy

We report the first successful realization of room-temperature laser action at a wavelength of 1.55 μm in a new double heterostructure in which the active layer of GaxAlyIn1−x−yAs is confined between two cladding layers of AluIn1−uAs. The structure was grown on InP by molecular beam epitaxy, and was pumped optically by a Q-switched yttrium aluminum garnet laser. Peak output power of up to 5 W was obtained at an incident power corresponding to four times that required for threshold without catastrophic degradation. Temperature dependence of the threshold power can be characterized by Pth∼exp(T/T0) with T0=60 °C for 20 °C≤T≤100 °C.

Laser action in trans-1,1,4,4 tetraphenyl-butadiene: Evidence for stimulated emission from two different species

Experimental results concerning laser action as a function of temperature of trans-1,1,4,4 tetraphenyl-butadiene in cumene are reported. At room temperature laser action is observed at 4980 Å, whereas between -70°C and -80°C laser action occurs simultaneously at 4980 Å and 4350 Å, and below -80°C only emission at 4350 Å is observed. The normal fluorescence of trans-1,1,4,4 tetraphenyl-butadiene exhibits a maximum at 4550 Å, byt a new emission band with a maximum near 5040 Å appears for high excitation energies below the lasing treshold. The intensity of this new band increases non-linearly with the excitation intensity. At low temperatures and high excitation energies this band disappears. It is concluded that at room temperature the laser effect in this compound arises from a photochemical species formed from the first excited singlet state of trans-1,1,4,4 tetraphenyl-butadiene. It is suggested that this species is a photoisomer and different hypotheses are discussed.

Laser emission at 1.065 μm from neodymium-doped anhydrous cerium trichloride at room temperature

Room-temperature laser action is reported in Nd3+ : CeCl3. The observed threshold was 0.06 J compared to 0.13 J for Nd3+ : YAG. Stronger pump bands and higher laser transition cross sections of neodymium-doped anhydrous trichlorides of cerium and lanthanum render these materials superior to Nd3+ : YAG for miniaturized and thin-film laser applications.

High-efficiency Nd3+ : LiYF4 laser

Pulsed room-temperature laser action has been observed in Nd3+ : LiYF4 at 1053 nm. A threshold of 8 J and a slope efficiency of 0.82% was obtained with a 60% reflectivity output mirror. These results are compared to Nd3+ : YAG data taken in the same cavity. Loss coefficients are calculated for each material and are compared.

Surface Lasers

Room-temperature visible laser action is reported in PrCl3 and PrBr3. Optical pumping directly into the upper laser level is accomplished by a wavelength-tunable dye laser. Threshold is less than 1 μJ. Superradiant laser action within physical dimensions of a few microns is generated by focusing the excitation light on the cleaved crystal surface. Use as an active element in integrated optics networks is indicated with over 106 individual lasers per square inch.

High-Efficiency Room-Temperature 2.06-μm Laser Using Sensitized Ho3+:YLF

Pulsed room-temperature laser action at 2.06 μm has been achieved using Ho3+:YLF (LiF4) sensitized with Er3+ and Tm3+. An unoptimized cavity gave a threshold of 35 J and a slope efficiency of 1.3% in normal mode with an output mirror of 62% T. A slope efficiency of 2% and a 65-J threshold were observed in Q-switched operation along with Q-switched energy of &amp;gt;500 mJ from a 0.9×⅛-in. rod. The sensitizer ions have broad absorption bands and transfer times (to the active ion) of 150–200 μsec.