Generation Of Ultraviolet Light Research Articles

The role of the torsion of the phenyl moiety in the mechanism of stimulated ultraviolet light generation in 2-phenylbenzazoles

The general difference observed between the photophysical behavior of 2-phenylbenzazoles and parent unsubstituted benzazole is explained through an exchange of the energy order of the two lower excited singlet states of both compounds. The energy variation takes place because S1 -excited 2-phenylbenzazoles suffer a subnanosecond conformational change towards planarity by torsion around the phenyl-heterocycle bond. This torsion is in accordance with theoretical calculations, with ultraviolet (UV)-visible and fluorescence data, and with results obtained on rotationally-constrained 2-phenylindoles. These changes, as well as the usually high fluorescence quantum yields and small Stokes shifts exhibited by unsubstituted benzazoles, make 2-phenylbenzazoles suitable dye lasers for the UV-zone of the spectrum.

Theory of guided-wave frequency tripling in the form of coherent Čerenkov radiation: Application to ultraviolet light generation

A useful wave-optics solution is derived for the Čerenkov mode calculation of optical third-harmonic signals that are generated in a multilayer planar optical waveguide. With this modal solution, the ultimate performance of the planar-configuration frequency tripler, being phase matched in the form of coherent Čerenkov radiation, is predictable. Numerical results are shown for the third-harmonic ultraviolet light generation in a planar glass waveguide loaded by a polydiacetylene Langmuir–Blodgett deposited thin film. Furthermore, the possibility of pronounced activation of the third-harmonic radiation from a glass waveguide pumped by an intense laser beam is suggested through field calculations based on a laser-induced damage model. In addition, loss analysis that includes both one- and two-photon absorptions is made by means of a phenomenological propagation model using coupled rate equations.

Generation of continuous-wave ultraviolet light by sum-frequency mixing of diode-laser and argon-ion-laser radiation in β-BaB_2O_4

More than 1 microW of tunable continuous-wave radiation at 369 nm has been generated by sum-frequency mixing of the radiation from a 1310-nm diode laser with the radiation from a 515-nm argon-ion laser in a beta-BaB(2)O(4) crystal. The phase-mismatching tolerance for nearly optimum focusing of input beams was found to be several times as large as that for no focusing or the calculated value. This effect was caused by relatively large double refraction of beta-BaB(2)O(4).

Third-harmonic generation of an alexandrite laser in β-BaB2O4

We report the first cascading third-harmonic generation by light from an alexandrite laser in β-BaB2O4. Ultraviolet (UV) light was generated by mixing the fundamental laser light with the second-harmonic light. The calculated effective nonlinear constant for type I mixing is nearly three times larger than that for type II. Using type I mixing we demonstrated UV light generation in the wavelength region 244–259 nm with 24% mixing efficiency at maximum.

Observation of sub-Poisson Franck–Hertz light at 2537 nm

We report the generation of ultraviolet (253.7-nm) sub-Poisson light from Hg vapor excited by inelastic collisions with a space-charge-limited (quiet) electron beam. This first stationary sub-Poisson light source is only weakly so, with a Fano factor that is between two and three standard deviations below that for Poisson light. This is principally because of optical losses in the experimental apparatus. There does not appear to be any fundamental limit that impedes the techniques from being used to produce an intense cw light source that is also arbitrarily sub-Poisson.

Ultraviolet sum-frequency generation utilizing optical pair interactions in solids

We report the first observation of nonlinear generation of broadband ultraviolet light by pair interactions in a solid. Emission from PrF 3 on numerous features between 270–410 nm is ascribed to transitions of coupled atoms. They occur at sum-frequencies of known Pr 3+ intraconfigurational transitions and show quadratic dependence on input power. High intensities and structured excitation spectra are observed. The prospect of stimulated ultraviolet pair emission with visible light excitation is examined.

Sum-frequency generation via a resonant quadrupole transition in sodium

We show that second-order nonlinear optical processes such as sum and difference generation can be observed in isotropic media, despite the fact that such processes are forbidden in the electric-dipole approximation. A theoretical treatment of quadrupole sum- and difference-frequency generation is given, which includes the effects of spin-orbit and Zeeman splittings. The quadrupole nonlinear susceptibility is evaluated and expressions for phase matching and output power are found. We have generally confirmed the theoretical predictions by observing quadrupole sum-frequency generation of ultraviolet light in sodium vapor. Deviations of the data from the simple theory can be satisfactorily accounted for by the effects of two-photon saturation, induced index of refraction changes, and single- and multi-photon absorption. Generalization of the dipole forbidden susceptibilities to the case of quadrupole-pumped processes is discussed, with difference-frequency generation in Cs vapor considered as an example.