Clifford R. Pollock

Efficient continuous-wave chromium-doped YAG laser

Continuous-wave power performance of a chromium-doped YAG laser pumped by a Nd:YAG laser is investigated as a function of crystal temperature, output coupling transmission, and emission wavelength. Using a 2%-transmitting output coupler, we obtained as much as 1.9 W of cw output power at 1.45 μm with an absorbed power slope efficiency of 42% when the gain medium was cooled at 3°C. Using the laser efficiency data, we estimated the emission and excited-state absorption cross sections at 1.45 μm and compared them with the previously reported values.

Passive Q switching of a diode-pumped Nd:YAG laser with a saturable absorber

A diode-pumped Nd:YAG laser is passively Q switched by using F(2)(-) color centers in lithium fluoride as a saturable absorber. When cw pumped with a laser diode, the laser produces pulses of 20-30-nsec duration at 1064 nm, with an energy of as much as 20 microJ and a peak power of more than 1 kW. Data are presented on pulse width, energy, and repetition rate as a function of pump power. When the laser is operated at high pulse energy levels, a gradual bleaching of the saturable absorber is observed.

Additive-pulse mode-locked NaCl:OH − laser

The operation of an additive-pulse mode-locked NaCl:OH(-) color-center laser is described. Stable output pulses as short as 75 fsec have been obtained. The laser is tunable from 1.51 to 1.65microm, with 300 mW of average output power at 1.6 microm.

Continuous-wave operation of the KBr:CN− solid-state vibration laser in the 5-μm region

Continuous-wave lasing has been obtained on the 2 → 1 vibrational transition of impurity CN− ions in KBr. Population inversion is produced by optical pumping of the weakly allowed first-overtone level of the molecule with a tunable (F2+)A color-center laser.

AMPLIFICATION BY OPTICAL COMPOSITES

Optical amplification is demonstrated in waveguides of composite materials consisting of nanocrystals of Cr:forsterite or Cr:diopside embedded in a host polymer with a matching refractive index. Small-signal gains of 1dB / cm at lambda=1.23microm are reported.

Continuous-wave self-mode-locked operation of a femtosecond Cr 4+ :YAG laser

Continuous-wave self-mode-locked operation of a chromium-doped YAG laser pumped by a continuous-wave Nd:YAG laser at 20 degrees C is described. We used both regenerative initiation and continuous-wave self-mode-locking techniques to generate nearly transform-limited pulses of 120-fs (FWHM) duration at 1.52 microm. The TEM(00) output power was as high as 360 mW. The output of this femtosecond source was tunable from 1.51 to 1.53 microm.

Stable color-center laser in OH-doped NaCl operating in the 1.41- to 1.81-μm region

A powerful and stable color-center laser based on a perturbed F(2)(+) center has been demonstrated in additively colored NaCl:OH(-) crystals. The OH(-) impurity has been positively identified as the key dopant for creating the color-center laser in NaCl. The laser tunes smoothly over the 1.41- to 1.81-microm region with a maximum cw power of 1.25 W when pumped by a 9-W cw Nd:YAG laser operating at 1.06 microm. Laser operation for periods of several weeks has been monitored with no observable fading in output power. In addition, mode-locked pulses of 5-psec duration have been generated in a synchronously pumped arrangement, tunable from 1.47 to 1.73 microm with an average power of 450 mW at the peak of the tuning curve.

Mode-locked Cr 2+ :ZnSe laser

We describe active mode locking of a Cr(2+):ZnSe laser operating near 2.5 mum. The laser produces 4.4-ps transform-limited Gaussian-shaped pulses and produces 82 mW of average power.

Performance of a continuous-wave forsterite laser with krypton ion, Ti:sapphire, and Nd:YAG pump lasers

The authors characterize continuous-wave operation of a chromium-doped forsterite (Cr/sup 4+/:Mg/sub 2/SiO/sub 4/) laser using krypton ion, Ti:sapphire, and Nd:YAG lasers as pump sources. Measurements were made pumping at 647 nm and 676 nm with the krypton ion laser, between 690 and 1010 nm with the Ti:sapphire laser, and at 1.06 mu m with the Nd:YAG laser. Threshold pump powers and slope efficiencies are compared for output coupler transmissions varying between 1 and 15.5%. Room-temperature operation was only achieved using the Nd:YAG pump laser. Forsterite laser output power as a function of both temperature and pumping wavelength is discussed. >

Generation of tunable femtosecond pulses in the 1.21-1.27 /spl mu/m and 605-635 nm wavelength region by using a regeneratively initiated self-mode-locked Cr:forsterite laser

A detailed description of the design and operational characteristics of a regeneratively initiated, self-mode-locked Cr:forsterite laser pumped by a continuous-wave Nd:YAG laser is given. Without compensating for the intracavity positive group velocity dispersion, regenerative acoustooptic modulation produced pulses of between 41 and 6.5 ps (FWHM) at 1.23 /spl mu/m with average output powers of between 280 and 380 mW, respectively. Using intracavity negative group-velocity-dispersion compensation, nearly transform-limited femtosecond pulses of 48 fs (FWHM) duration were generated with average TEM/sub 00/ output powers of 380 mW at 1.23 /spl mu/m. By tuning the output of the mode-locked laser from 1.211 to 1.264 /spl mu/m, the dispersion (second and third order) of the Cr:forsterite gain medium has been measured. The operational wavelength range of the laser was extended to the visible region from 605 to 635 nm by external frequency doubling in a LiIO/sub 3/ nonlinear crystal. With approximately 250 mW of fundamental pump power at 1.23 /spl mu/m, red pulses of 116 fs (FWHM) duration at 615 nm were obtained with conversion efficiencies approaching 10 percent. >