Ross A. McFarlane

Direct observation of laser‐induced solid‐phase epitaxial crystallization by time‐resolved optical reflectivity

Direct measurement of solid phase epitaxial crystallization during cw laser annealing of ion‐implanted silicon is reported. The measurement technique utilizes optical interference effects between reflected light from the sample surface and from the epitaxial growth plane to time‐resolve the growth process with high spatial resolution. Laser‐induced solid phase epitaxial growth was monitored for two values of incident laser power; corresponding epitaxial growth rates and calculated surface temperatures are given.

Dual wavelength visible upconversion laser

Laser operation has been obtained at 551 and 671 nm by pumping 5% Er:YLiF4 at 791 nm. Time dependence studies of the emission show that the excitation process has a component related to cooperative energy transfer, and a component related to stepwise multiple photon absorption. Self‐Q‐switched operation at 551 nm is seen to impart a time dependence to an otherwise cw output at 671 nm.

High-power visible upconversion laser

Laser output power approaching 0.5 W cw has been obtained at 551 nm by using upconversion pumping of YLiF4:Er 5%. A power slope efficiency of 14% has been determined, and the output coupling for the available pump power has been optimized at 797 nm.

Upconversion laser in BaY 2 F 8 :Er 5% pumped by ground-state and excited-state absorption

Upconversion laser emission has been achieved in BaY2F8:Er 5% by pumping of either the ground state or an excited state of the Er3+ ion. The initial excitation step has been identified with precise measurement data of the Stark level structure of the Er3+ ion in this system. Small increments in the pump wavelength can cause the laser to switch from laser operation in the blue to laser operation in the green because of changes in the specific pumping pathway.

Laser oscillator using resonator with self-pumped phase-conjugate mirror.

A laser oscillator has been operated in which one reflector is a self-pumped phase-conjugate mirror. The laser is tunable and employs rhodamine 6G as a broadband gain medium. The oscillating linewidth was measured to be 2 GHz at half-power points.

Photoacoustic measurements of ion‐implanted and laser‐annealed GaAs

Photoacoustic techniques were developed for use as a rapid and sensitive diagnostic of crystalline disorder produced by ion implantation in gallium arsenide. With a 150‐keV silicon implant, doses as low as 1012 cm−2 were detectable. Recrystallization of ion‐implanted gallium arsenide by laser annealing is readily detected by the photoacoustic method.

Investigation of diode-pumped 2.8-µm laser performance in Er:BaY2F8

Laser operation at 2.8 mm in BaY2F8 with erbium concentrations of 7.5% and 20% is investigated under laser-diode pumping at 967 nm. Output powers as high as 250 mW and slope efficiencies as high as 24% are obtained. Results are comparable with those of Er3+:LiYF4 under the same pump conditions. Slope efficiencies above 30% are predicted for optimized erbium concentrations.

Diode-pumped upconversion laser with 100-mW output power

A high-power semiconductor diode-laser array operating at 797 nm has been used to pump an Er:YLiF(4) upconversion laser with output at 551 nm operating at 48 K. By carefully controlling the beam geometry and oscillating linewidth of the diode-pumped laser, it has been possible to obtain 100 mW of visible output power with a conversion efficiency from the IR to the visible of greater than 5%.

Investigation of diode-pumped 2.8-{bold {mu}}m laser performance in Er:BaY{sub 2}F{sub 8}

Laser operation at 2.8 mm in BaY2F8 with erbium concentrations of 7.5% and 20% is investigated under laser-diode pumping at 967 nm. Output powers as high as 250 mW and slope efficiencies as high as 24% are obtained. Results are comparable with those of Er3+:LiYF4 under the same pump conditions. Slope efficiencies above 30% are predicted for optimized erbium concentrations.

Orientation-dependent fluorescence studies and spectroscopic analysis of doped barium yttrium fluoride upconversion laser crystals (BaY 2−x−y Yb x Tm y F 8 )

Crystals of BaY1.75Yb0.24Tm0.01F8,BaY1.50Yb0.49Tm0.01F8, and BaY1.00Yb0.99Tm0.01F8 grown by the gradient-freeze method under a hydrogen fluoride atmosphere operate as lasers at 348, 456, 482, 512, and 649 nm when upconversion pumped at 960 nm. The 649-nm red lasers show a clear orientation dependence; lasing is observed only when propagation is perpendicular to the crystallographic [010] direction. The orientation dependence of the red fluorescence confirms that the laser transition is exclusively polarized parallel to [010]. Ellipsoidal representations of intensities are determined from fluorescence data for several red and blue transitions. A crystal with composition BaY1.75Yb0.20Tm0.05F8 is considered as representative of the upconversion laser media. Stark levels for the 3H6,3F4,3H5,3H4,3F3,3F2,1G4,1D2, and 1I6 states are determined from absorption and fluorescence over a range of temperatures from 10 to 298 K. A Judd–Ofelt analysis that averages data for three orthogonal polarizations is also performed.