The future of lasers in onychomycosis.

Introduction: Laser therapy is one of the most promising device-based therapies for onychomycosis. To date, reported clinical efficacies, as well as anecdotal clinical results, have varied greatly, and the specific mechanism of action has not been well-elucidated.

Methods: Here, we provide an overview of the mechanisms of action and detailed analysis of the technical parameters involved in creating a laser that will be successfully fungicidal in onychomycosis.

Single-mode operation of a standing wave miniature Nd laser pumped by laser diodes.

Single-longitudinal-mode operation is reported for miniature Nd:YAG and Nd:BEL standing wave resonators. The best performance obtained was 18 mW with laser diode pumping and 31 mW with dye laser pumping. The miniature lasers were also operated multimode at power levels as high as 470 mW.

Birefringence of solid-state laser media: broadband tuning discontinuities and application to laser line narrowing.

Spectral consequences that result from using birefringent media with broadband gain inside of laser cavities containing polarizing elements are described. We show that the laser intensity is modulated as a function of the output frequency unless the cavity elements are carefully aligned so that their polarization axis coincides with a principal optical axis of the gain medium. Analysis of the tuning characteristics of a birefringent polarizationdependent gain medium is exploited to provide a simple method for line narrowing the laser output.

Thermodynamic bound on the phase-conjugate correction of optical distortions.

We show that there is a limit to the maximum efficiency achievable for correcting optical distortion (beam healing) using phase conjugation. This limit is quantum thermodynamic and stems from the impossibility of reducing the beam entropy by a lossless retrace of the phase aberrator.

The two-photon laser-induced fluorescence of the tumor-localizing photosensitizer hematoporphyrin derivative. Resonance-enhanced 750 nm two-photon excitation into the near-UV Soret band.

The tumor-localizing photosensitizer hematoporphyrin derivative (HPD) is shown to undergo a simultaneous two-photon excitation into the near-ultraviolet Soret band system upon intense laser irradiation at 750 nm, a spectral region where there is no significant HPD one-photon absorbance in aqueous solution. Subsequent to this excitation, internal conversion and vibrational relaxation occur, resulting in the population of the vibrationless level of the first electronically excited singlet state. This state relaxes by two channels, the emission of fluorescence in the spectral region 600-700 nm and intersystem crossing into the triplet manifold, followed by near-resonant electronic energy transfer with surrounding oxygen to result in the generation of highly reactive singlet molecular oxygen (1 delta g).

Moiré optical spatial correlator.

A new optical method to obtain the spatial-correlation integral of moiré maps is described and demonstrated. This method permits the direct and quantitative determination of the optical spatial correlation between two objects. The method can be applied to any optical quantity mapped by any moiré technique.