ABSTRACT
We obtained coherent radiation in the spectral region between 223 and 243 nm by frequency mixing the tunable output of a solid-state Ce(3+):LiCAF laser with 1.064-mum radiation from a Nd(3+):YAG pump laser in a beta-barium borate nonlinear crystal.
ABSTRACT
The performance of a flash-lamp-pumped Cr:LiSAF unstable laser resonator utilizing a fourth-order super-Gaussian variable reflectivity mirror as an output coupler is described. The super-Gaussian mirror results in a smooth, flattop transverse beam profile in the near field that is advantageous for nonlinear frequency-conversion applications. Long-pulse and Q-switched operation of the Cr:LiSAF unstable laser resonator are described and compared with stable resonator operation. We obtained tunable ultraviolet radiation extending from 267 to 290 nm by frequency mixing theQ-switched Cr:LiSAF laser output with lithium triborate and beta-barium borate nonlinear crystals.
ABSTRACT
Room-temperature, continuous-wave laser action at 2.3 microm corresponding to the (3)H(4)-(3)H(5) transition in Tm(3+)- doped YLF is achieved. Output powers of 200 mW and a slope efficiency of 15% have been obtained for a pump power of 2 W at 0.78 microm. In addition, continuous tunability of this laser from 2.20 to 2.46 microm is obtained.
ABSTRACT
Continuous-wave mode-locked operation of a 2-microm Tm: YAG laser is demonstrated. Stable, transform-limited pulses of 35-ps duration have been generated at a repetition rate of 300 MHz, with an average output power of 70 mW.
ABSTRACT
The 2.09-microm Ho:YAG (5)I(7) ? (5)I(8) 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-microm Tm(3+) laser emission pumps the Ho:YAG crystal. The slope efficiency of the 2.09-microm Ho(3+) laser output is 42% of the absorbed 785-nm pump power.
ABSTRACT
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.
ABSTRACT
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.
ABSTRACT
We report what is to our knowledge the first room-temperature operation of an efficient flash-lamp-pumped Cr,Tm:YAG laser at 2.014 microm. Thresholds as low as 43 J, output energies exceeding 2 J, and slope efficiencies as high as 4.5% have been achieved using a compact diffuse-reflecting pump cavity. These efficiencies are an order of magnitude higher than those previously reported for a 2.01-microm Cr,Tm:YAG laser operated at cryogenic temperatures.
ABSTRACT
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.
ABSTRACT
We have achieved efficient room-temperature flash-lamp-pumped laser operation in titanium-doped sapphire. The laser has a threshold of 20 J, a slope efficiency of 0.5%, an output energy in excess of 300 mJ, and a tuning range (with our present optics) of 720-920 nm. Ways of reducing the lasing threshold and increasing slope efficiency are discussed.
ABSTRACT
Irreversible laser damage phenomena are investigated in pyroelectric and semiconductor ir detector materials. Thermal damage phenomena in these materials are reviewed, and new results are presented. Theoretical models, which successfully describe thermal damage in detector materials, are reviewed, and criteria for the application of these models are discussed.
ABSTRACT
An experimental method for measuring the transient and steady-state thermal characteristics of ir photoconductors is introduced. Thermal recovery processes in laser irradiated HgCdTe (PC) detectors were investigated. The characteristics of thermal recovery processes are found to be quite sensitive to the specific details of detector construction. For the most part thermal recovery in these detectors takes place on two separate time scales. Initially the signal recovers partially to an intermediate level on a time scale of several milliseconds. The rest of the recovery occurs much more slowly, i.e., on the order of hundreds of milliseconds. It was found that the magnitude of the thermally induced signal, the relative importance of the two recovery processes, and the exact shape of the thermal recovery curve vary with power density and irradiation time. A one-dimensional thermal model of the detector for both pulsed and cw laser irradiation is presented. Calculated thermal recovery curves are found to agree we l with the experimental results for irradiation times as long as 20 msec. The two recovery times are found to be due to the two thermally resistive bonding layers. The utility of this model for predicting the thermal characteristics of new improved detector designs is discussed.
ABSTRACT
An analysis of an ideal five-level ir quantum counter (IRQC) is presented. The importance of the two additional levels is discussed and analyzed. The parameters for achieving optimum performance as an ir detector and/or an image converter are presented. In theory, the IRQC is the only quantum amplifier with photon gain that can approach a noise temperature of absolute zero. In practice, with the constriction of available materials and technology, the most feasible use for the IRQC in the near term would be in an active system. An ir laser would be used to scan the target while another laser would pump the excited state transition. The IRQC action has been observed in this laboratory in the tripositive rare earths of Pr, Nd, Eu, Tb, Dy, Er, and Tm. These ions were incorporated in single crystal lattices of CaF(2), BaF(2), SrF(2), CdF(2), LaF(3), CaWO(4), A1(2)O(3), YAG, LaCl(3), and in solutions of the various trichlorides (dissolved in D(2)O). A total of 165 schemes are reported. The rare earth impurity concentration varied from 0.05% to 20%. In our laboratory, the primary range of interest for detection and/or image conversion is between 1 micro and 2 micro. Therefore, almost all the systems studied involved the detection of an ir photon in this region.
