Robert C. Stoneman

Efficient, broadly tunable, laser-pumped Tm:YAG and Tm:YSGG cw lasers

Broadly tunable cw laser emission is reported in Tm:YAG and Tm:YSGG at room temperature with Ti:sapphire laser pumping. The Tm(3+)(3)F(4) ? (3)H(6) transition is tuned continuously over the ranges 1.87-2.16 microm in YAG and 1.85-2.14 microm in YSGG. Smooth tuning results from overlapping transitions between phonon-broadened crystal field Stark levels.

Intracavity-pumped 2.09-μm Ho:YAG laser

The 2.09-μ Ho:YAG 5I7 → 5I8 laser transition is intracavity pumped by a Tm:YAG laser. Separate Tm:YAG and Ho:YAG crystals share a single laser cavity, the Tm:YAG crystal is pumped at 785 nm, and the resulting 2.01-μm Tm3+ laser emission pumps the Ho:YAG crystal. The slope efficiency of the 2.09-μm Ho3+ laser output is 42% of the absorbed 785-nm pump power.

Efficient resonantly pumped 2.8-μm Er 3+ :GSGG laser

Efficient cw operation of the Er(3+):GSGG (4)I(11/2)?(4)I(13/2) laser transition at 2.8 microm is demonstrated at room temperature. The (4)I(11/2) upper laser state is directly pumped at 0.97 microm. The slope efficiency for the 2.8-microm laser is 36%, indicating a greater than unity quantum efficiency. This excess efficiency results from the recycling of population through upconversion out of the lower laser state.

Direct upper-state pumping of the 2.8 mu m, Er/sup 3+/:YLF laser

Direct resonant pumping of the /sup 4/I/sub 11/2/ upper state of the 2.8- mu m Er/sup 3+/:YLF laser at 0.97 mu m is shown to be more efficient than other pumping schemes which have been used for this transition. Upper-state pumping avoids nonradiative losses arising from phonon and self-quenching decays inherent in other pumping schemes. Efficient performance of the 2.8- mu m laser is maintained on condition that extremely shallow pump absorption is avoided. Reduced efficiency for shallow pump absorption is attributed to upconversion loss arising from high pumping rates. >

Continuous-wave 1.50-μm thulium cascade laser

A cascade laser scheme is used to obtain continuous-wave 1.50-microm laser emission at room temperature on the normally self-terminating Tm(3+)(3)H(4) ? (3)F(4) transition in YLiF(4). The long-lived (3)F(4) state is quenched through energy transfer to the Ho(3+)(5)I(7) state, which is depopulated through the Ho(3+)(5)I(7) ? (5)I(8) 2.06-microm laser transition.

High power Q-switched Tm:YAlO3 lasers

We have demonstrated 50 W of output power from a free-running Tm:YAlO3 laser at 1940 nm. We have also obtained Q-switched operation with 7 mJ of output energy at a 5 kHz repetition rate.

Coherent laser radar using eyesafe YAG laser transmitters

We report the development of an eyesafe YAG laser for coherent laser radar wind sensing applications. The upper-state pumped 1.6 mm Er:YAG laser produces high pulse energies with diffraction-limited beam quality.

High-power eyesafe YAG lasers for coherent laser radar

We report developments of high-power eyesafe YAG lasers for coherent laser radar applications. Upper-state pumped 2.1 μm Ho:YAG and 1.6 μm Er:YAG lasers produced output powers greater than 7 W with diffraction-limited beam quality.

Eyesafe diffraction-limited single-frequency 1-ns pulsewidth Er:YAG laser transmitter

We report an eyesafe diffraction-limited single-frequency 1617 nm Er:YAG laser transmitter for coherent laser radar applications. The transmitter utilizes a master oscillator/power amplifier architecture, enabling the production of high peak power output. The pulsed oscillator is Q-switched and cavity-dumped, resulting in a 1.1 ns pulsewidth. The pulsed oscillator is injection-seeded by a commercial 1617 nm CW distributed feedback laser diode, resulting in single longitudinal mode output. The oscillator and amplifier are directly pumped into the Er:YAG laser upper state by commercial diode-pumped CW 1533 nm Yb,Er-doped fiber lasers. The injection-seeded pulsed oscillator produces an average output power of 2.2 W at 10 kHz pulse repetition frequency (PRF) with a pulsewidth of 1.1 ns (0.20 MW peak power) with a beam quality 1.1 times the diffraction limit. The oscillator has a slope efficiency of 47% in the CW mode, and a conversion efficiency of 85% from CW mode to injection-seeded pulsed mode. The power amplifier produces 20 W in the CW mode with an optical-to-optical conversion efficiency of 34% and a beam quality 1.1 times the diffraction limit, and 6.5 W in the pulsed mode at 10 kHz PRF with 1.1 ns pulsewidth (0.59 MW peak power).

Trivalent thulium laser at 1.95 μm for enhanced laser-tissue interactions

Solid state lasers based on the trivalent thulium ion which operate within the strong water absorption band in the 2zin region are discussed. This water band has maximum absorption in the range 1.92- 1.94pm. The relative merits of thulium lasers in the crystalline hosts YAG, YSGG, and YLF which operate in this wavelength region are discussed.