Richard Scheps

Alexandrite laser pumped by semiconductor lasers

We report the first operation of a direct diode‐pumped tunable chromium‐doped solid‐state laser. A small alexandrite (Cr:BeAl2O4) crystal was longitudinally pumped by two visible laser diodes. The threshold pump power was 12 mW using the R1 line at 680.4 nm for the pump transition, and the slope efficiency was 25%. The measured laser output bandwidth was 2.1 nm.

Influence of large amplitude vibrational motion on the rate of intersystem crossing: A study of single vibronic level fluorescence from aniline‐h7, aniline N, N‐d2, aniline‐d5, and aniline‐d7

Results of single vibronic level fluorescence measurements in aniline‐h7, aniline‐N, N‐d2, aniline‐d5, and aniline‐d7 are reported. For each excited level the radiative and nonradiative lifetimes and fluorescence yields have been obtained. The dependence of the nonradiative lifetime of the excited level on the excess energy in aniline‐h7 is seen to behave similarly to that in benzene for states independent of inversion mode excitation. Levels involving inversion amplitude must be treated separately; we interpret their lifetimes by postulating that a nonplanar triplet state is involved in the intersystem crossing. Deuteration in the ring and amino positions affects the nonradiative lifetimes to different degrees and leads to the rejection of crossing to the 3B2 state as the rate determining step. A detailed study of the dependence of the nonradiative process on excitation of the inversion mode was carried out using the methods of Heller, Freed, and Gelbart. The numerical calculations were based on Franck‐C...

Interference Effects in the Rydberg Spectra of Naphthalene and Benzene

We report new studies of (portions of) the Rydberg spectra of naphthalene and benzene. The anti‐resonances in the Rydberg spectrum of naphthalene are analyzed in terms of the theoretical line‐shape parameters A [Eq. (3)], q [Eq. (4)], and Γ [Eq. (6)]. The values of the parameters deduced, together with a simple physical argument, imply that the matrix element coupling the zero‐order Rydberg state φR and the isoenergetic inhomogeneously broadened background levels {ψi} is less than 1 cm−1. The available data do not permit an unambiguous determination of the nature of the background transitions, and hence of the coupling mechanism. Two limiting cases are considered, one requiring strict compliance with symmetry properties of the zero‐order states, and one disregarding said symmetry properties because of vibronic mixing prior to the interaction of φR and {ψi}. Both schemes can be made to fit the experimental data, and both have deficiencies. A possible intermediate scheme is suggested; it requires the backgr...

Efficient laser diode pumped Nd lasers

Results are presented for laser diode axially pumped Nd:YAG and Nd:BEL lasers. For Nd:YAG, in excess of 870 mW was obtained with a differential slope efficiency of 56%, and for Nd:BEL in excess of 635 mW was obtained with a slope efficiency of 46%. Electrical efficiencies of 13.0 and 9.5% were recorded for Nd:YAG and Nd:BEL, respectively. The overall efficiency is factored into a product of efficiency terms, and good agreement with experimental result was found.

Cr:LiCaAlF/sub 6/ laser pumped by visible laser diodes

A Cr:LiCaAlF/sub 6/ laser was pumped using visible lase diodes. Two commercial 10-mW laser diodes were polarization combined to demonstrate lasing in a low-loss resonator. In addition, a higher power 665-nm laser diode was used to pump the laser, producing 15.9 mW CW and 51.8 mW pulsed at 10 Hz. Optical characterization of the gain medium was performed using a dye laser. Gain, loss, slope efficiency, and the dependence of the threshold power on pump wavelength are reported. >

Doubly resonant Ti:sapphire laser

A CW Ti:sapphire laser that operates simultaneously at two frequencies is described. This mode of operation was obtained with an intracavity dispersive prism and two separate feedback paths. An alternative means of achieving dual frequency operation was demonstrated using a birefringent filter. Repetitive Q-switching produced an increase in the range of wavelengths over which dual frequency operation was obtained.<<ETX>>

A single frequency Nd:YAG ring laser pumped by laser diodes

The design and operation of a diode-pumped Nd:YAG ring laser is described. The laser is shown to be a highly versatile device, capable of efficient generation of both the fundamental and second harmonic frequencies, CW and Q-switched. Single-frequency outputs in excess of 540 mW at 1.06 mu m and 18.9 mW at 532 nm output were obtained, whereas multi-longitudinal mode Q-switched operation produced 22.4 mu J per pulse at 5 kHz in the fundamental and 7.3 mu J power pulse at 532 nm. >

High-efficiency 1.06-μm output in a monolithic Nd:YVO 4 laser

A miniature 1.5-mm-long monolithic Nd:YVO(4) laser was end pumped with a Ti-sapphire laser. The Nd-doping density was 3 at. %. The maximum output power obtained with 885 mW of absorbed pump power was 495 mW at 1.064 µm. The maximum slope efficiency was 57%, and the output power was only slightly dependent on pump polarization. Laser diode pumping was also demonstrated. Thermal effects were observed to reduce the output power and required active cooling of the laser crystal.

Monochromatic end-pumped operation of an alexandrite laser

Abstract Operation of an alexandrite laser pumped by short wavelength visible laser diodes is described. Two polarization-combined 640 nm diodes produced 25 mW output at 753 nm. Characterization measurements were performed with a dye laser. The best slope efficiency measured was 63.8%, close to the calculated intrinsic efficiency and the highest reported for a Cr 3+ -doped laser. The threshold power was 5.5 mW and the measured passive resonator loss was 0.06%/cm.

PERFORMANCE OF A DIODE-PUMPED LASER REPETITIVELY Q-SWITCHED WITH A MECHANICAL SHUTTER

Repetitively Q-switched operation of an end-pumped Nd:YAG laser over the range of 200 Hz to 3 kHz using an intracavity chopper is demonstrated. Performance is shown to be comparable to that achieved with an acousto-optic Q switch under similar conditions. The advantages and limitations of the mechanical Q switch are described. Parametric variations of output coupling and pump power lead to an extended empirical description of repetitively Q-switched laser operation. The insertion loss as a function of aperture-edge penetration into the resonator is reported, and a definition of the mechanical Q-switch opening time is provided. Q-switched pulsewidths as short as 35 ns were obtained for the Nd:YAG laser, with a peak power-enhancement factor in excess of 300.