Tunable alexandrite lasers

Wavelength tunable laser operation has been obtained from the solid-state crystal alexandrite (BeAl 2 O 4 :Cr3+) over the continuous range from 701 to 818 nm. The tunable emission was observed at room temperature and above in a homogeneously broadened, vibronic, four-level mode of laser action. In this mode the laser gain cross section increases from 7 \times 10^{-21} cm2at 300K to 2 \times 10^{-20} cm2at 475K, which results in improved laser performance at elevated temperatures. Efficient 2.5 percent, low-threshold (10 J) operation has been obtained with xenon-flashlamp excitation of the 6 mm diameter × 76 mm length laser rods. Output pulses of greater than 5 J and average power outputs of 35 W have been demonstrated, limited by the available power supply. The emission is strongly polarized E\parallelb , with a gain that is 10 times that in the alternate polarization. The 262 μs, room-temperature fluorescence lifetime permits effective energy storage and Q -switched operation. Tunable Q -switched pulses as large as 500 mJ have been obtained with pulsewidths ranging between 33 and 200 ns depending on the laser gain. Laser action has also been demonstrated on the high-gain ( 3 \times 10^{-19} cm2emission cross section) R line at 680.4 nm and is also polarized E\parallelb . This three-level mode is analogous to the lasing in ruby except that the stimulated emission cross section in alexandrite is ten times larger than for ruby.

[1]  D. Findlay,et al.  The measurement of internal losses in 4-level lasers , 1966 .

[2]  Y. Tanabe,et al.  On the Absorption Spectra of Complex Ions II , 1954 .

[3]  D. Mccumber,et al.  Einstein Relations Connecting Broadband Emission and Absorption Spectra , 1964 .

[4]  L. Johnson,et al.  Phonon-Terminated Optical Masers , 1966 .

[5]  L. Johnson,et al.  Electronic- and phonon-terminated laser emission from Ho 3+ in BaY 2 F 8 , 1974 .

[6]  L. Johnson,et al.  Optical Maser Oscillation from Ni^{2+} in MgF_{2} Involving Simultaneous Emission of Phonons , 1963 .

[7]  H. Jenssen,et al.  Tunable-laser performance in BeAl(2)O(4):Cr(3+). , 1979, Optics letters.

[8]  R. Morris,et al.  Tunable CW alexandrite laser , 1980 .

[9]  A. Mooradian,et al.  Efficient cw optically pumped Ni:MgF(2) laser. , 1978, Optics letters.

[10]  D. F. Nelson,et al.  Relation between Absorption and Emission in the Region of the R Lines of Ruby , 1965 .

[11]  D. Mccumber,et al.  Theory of Phonon-Terminated Optical Masers , 1964 .

[12]  L. Johnson,et al.  Spontaneous and stimulated emission from Co2+ ions in MgF2 and ZnF2 , 1964 .

[13]  T. E. Varitimos,et al.  Optical spectra and relaxation of Cr3+ ions in YAlO3 , 1974 .

[14]  O. Peterson,et al.  High gain laser performance in alexandrite , 1979, IEEE Journal of Quantum Electronics.

[15]  Hans P. Jenssen,et al.  Spectroscopic properties and laser performance of Nd3+ in lanthanum beryllate , 1976 .

[16]  C. W. Struck,et al.  Temperature dependences ofCr+3radiative and nonradiative transitions in ruby and emerald , 1975 .

[17]  L. Johnson,et al.  Phonon‐Terminated Coherent Emission from V2+ Ions in MgF2 , 1967 .

[18]  M. J. Weber,et al.  Nonlinear Refractive Index of Glasses and Crystals , 1978 .

[19]  O. Deutschbein.  Die linienhafte Emission und Absorption der Chromphosphore. II , 1932 .

[20]  H. Jenssen,et al.  Phonon-assisted laser transitions and energy transfer in rare-earth laser crystals , 1972 .

[21]  C. K. Asawa,et al.  Stimulated Optical Emission in Fluorescent Solids. II. Spectroscopy and Stimulated Emission in Ruby , 1961 .

[22]  W. Bond.  Measurement of the Refractive Indices of Several Crystals , 1965 .