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.

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.

Generation of 48-fs pulses and measurement of crystal dispersion by using a regeneratively initiated self-mode-locked chromium-doped forsterite laser.

A regeneratively initiated self-mode-locked chromium-doped forsterite laser operated at 3.5 degrees C is described. By employing intracavity negative-group-velocity dispersion compensation, nearly transform-limited femtosecond pulses of 48-fs (FWHM) duration were generated with average TEM(00) output powers of 380 mW at 1.23 microm. Regenerative initiation provides improvement in the output stability and ease of operation compared with fixed-frequency acousto-optic modulators. By tuning the mode-locked laser in the range 1.21-1.26 microm, estimated values for forsterite dispersion constants have also been obtained for the first time to our knowledge. The demonstrated power and stability open the door to applications such as efficient second-harmonic generation.

Femtosecond pulse generation by using an additive-pulse mode-locked chromium-doped forsterite laser operated at 77 K.

Using an acousto-optically mode-locked chromium-doped forsterite laser, operated at 77 K and coupled to a nonlinear resonator containing a single-mode fiber, we have produced femtosecond pulses of 150-fs duration at 1.23 microm with useful output powers of approximately 60 mW This represents what is to our knowledge the first demonstration of femtosecond pulse generation from this laser system using the coupled-cavity mode-locking scheme.

Tunable, cw operation of a multiwatt forsterite laser.

We have obtained over 1.8 W of power from a cw chromium-doped forsterite laser operated at 77 K when it is pumped by a 7.3-W Nd:YAG laser at 1.06 microm. The forsterite laser tunes smoothly from 1.2 to 1.32 microm. At room temperature the output power decreases to approximately 35% of the cryogenic power level.

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.

Frequency-doubled, additive-pulse, mode-locked NaCl:OH(-)laser.

The output of a tunable, additive-pulse, mode-locked NaCl:OH(-) color-center laser has been frequency doubled using a LiIO(3) crystal. With 100-fsec pulses generated at 1.6 microm, stable pulses as short as 76 fsec have been obtained with more than 5 mW of average output power at 0.8 microm. The frequency-doubled pulses are tunable from 755 to 825 nm.

Optically induced reorientational aggregation and the stability of F(2)(+) color-center lasers.

Spectroscopic evidence is presented showing that F(2) centers in KCI optically convert to an array of higher Faggregate centers at temperatures as low as 40 K. This aggregation occurs through random diffusion of F(2)(+) centers by means of repeated optical reorientation. Stable lasing of the F(2)(+) center has been achieved at a crystal temperature below which this reorientational aggregation ceases.

Fiber optic tachometer based on the Faraday effect.

A fiber optic tachometer is described that uses the Faraday effect in a ferrite to modulate light from a multimode fiber. A yttrium iron garnet (YIG) crystal is used as the magnetooptic modulator. A permanent magnet is placed near the crystal, such that a nearby rotating steel toothed wheel changes the magnetic field inside the crystal, causing modulation of the intensity of the 1.3-microm light. Modulation depths up to 50% have been achieved with signal-to-noise ratios of over 15 dB. A single multimode fiber connects the remote sensor head to the LED light source and detector.

Acousto-optic mode-locked soliton laser.

An acousto-optic modulator has been used to actively mode lock a KCl:Tl degrees (1) color-center laser at 1.5 microm. The color-center laser is capable of generating transform-limited pulses as short as 6 psec with 2-W cw pump power. Based on this actively mode-locked KCl:Tl degrees (1) laser a stable soliton laser has been operated, with performance similar to that of the synchronously pumped soliton laser.

Stable, pulsed, color-center laser in pure KCl tunable from 1.23 to 1.35 microm.

Stable, tunable, pulsed laser operation based on the N(2) color center in additively colored pure KCI is reported. The laser tunes smoothly from 1.23 to 1.35 microm when pumped by a 1.06-microm Q-switched Nd:YAG laser at kilohertz repetition rates. 42-mW average output power at 1.28 microm was achieved for 1-W average incident pump power. No power fading has been observed over several weeks of day-to-day operation.

(F(2)(+))(H) Color-center laser operation in NaCl:OH with simultaneous 1.06- and 0.53-microm pumping.

We have operated an (F(2)(+))(H) color-center laser in NaCl:OH using a 1.06-microm pump laser with a collinear auxiliary beam at 0.53 microm. The auxiliary beam is produced by frequency doubling a small fraction of the pump beam instead of using an arc lamp, as was previously reported. With a grating tuner, the laser tuned from 1.47 to 1 .8 7 microm and produced up to 760 mW of output power. In single-frequency operation, powers up to 460 mW with a linewidth <2 MHz were achievable. The laser also produced 480 mW of power in cw mode-locked operation with transform-limited pulses as short as 5 psec.

Pulsed, room-temperature operation of a tunable NaCl, color-center laser.

A room-temperature, pulsed, color-center laser using OH(-)-doped NaCl crystals is reported. Crystals were transversely pumped by a Q-switched Nd:YAG laser at 1.06microm and produced output energies of 8.6 mJ in 20-nsec pulses. The tuning range extended from 1.37 to 1.77 microm. During 40 h of operation (>10(6) pulses), a gradual power fading was observed. Laser action is tentatively ascribed to F(2)(+) centers.

Stable color-center laser in OH-doped NaCl operating in the 1.41- to 1.81-microm 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.

Continuous-wave operation of the KBr:CN(-) solid-state vibration laser in the 5-microm 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 (F(2)(+))(A) color-oenter laser.

Stable color-center laser in K-doped NaCl tunable from 1.42 to 1.76 microm.

Stable, broadly tunable cw lasing has been obtained from color centers in additively colored NaCl doped with K. The laser tunes from 1.42 to 1.76 microm with a peak output power of 530 mW when pumped by 6 W from a 1.06-microm Nd:YAG laser. Output power is strongly enhanced by exposing the crystal to an auxiliary UV light during lasing. No fading of output power has been observed over extended periods. The laser operates at 77 K; however, the crystals can be stored at room temperature. The active color center is tentatively identified as an (F(2)(+))(A) center.

Direct frequency measurements of transitions at 520 THz (576 nm) in iodine and 260 THz (1.15 microm) in neon.

The o hyperfine component of the (127)I(2) 17-1 P(62) transition at 520 THz (576 nm) in iodine was measured with respect to the CH(4)-stabilized 88-THz He-Ne laser. A 26-THz CO(2) laser, a color-center laser at 130 THz, and a He-Ne laser at 260 THz were used as transfer oscillators. The measured I(2) frequency was 520 206 808.547 MHz with a total fractional uncertainty of 1.6 x 10(-10). The 1.15-microm (20)Ne Lamb-dip-stabilized laser frequency was 260 103 249.26 MHz with a total fractional uncertainty of 3.1 x 10(-10).