Norman P. Barnes

Parametric generation processes: spectral bandwidth and acceptance angles

A systematic evaluation of the spectral bandwidth and two acceptance angles of parametric generation processes is presented. The spectral bandwidth and acceptance angles are determined by expanding the wave vector mismatch in a Taylor series and retaining terms through second order. This allows a determination of these parameters even when the first order term vanishes. Conditions where the first order term vanishes are presented and compared with similar cases where the first order term does not vanish.

Variation of the refractive index with temperature and the tuning rate for KDP isomorphs

The variation of refractive index with temperature is measured as a function of wavelength, temperature, and polarization for KDP and eight of its isomorphs. These data are used to predict the tuning rate for second-harmonic generation as a function of temperature. The predicted tuning rate compares well with the measured tuning rate. Reasonable agreement is found in most cases, the principal exceptions being those cases in which the data must be extrapolated significantly beyond the range of the measured values.

Temperature-dependent Sellmeier coefficients and nonlinear optics average power limit for germanium

A temperature-dependent Sellmeier equation is calculated for Ge. The accuracy of this temperature-dependent Sellmeier equation is compared with the internal consistency of the data. The phase-matching condition is discussed for four-wave mixing when two of the wave vectors are equal. The average power limit for four-wave mixing in a material like Ge is derived both for the case where one wave vector is fixed and for the case where two wave vectors are fixed. Using the derived Sellmeier equation, the average power limit for the four-wave mixing is calulated.

Temperature variation of the refractive indices of yttrium lithium fluoride

The temperature variations of the refractive indices of LiYF4, YLF, have been measured in the visible region of the spectrum. The temperature variation at 0.546 μm are −0.67×10−6/°C and −2.30×10−6/°C for the ordinary and extraordinary refractive indices, respectively. A Sellmeier equation was fit to more extensive room-temperature refractive-index data measured elsewhere.

Temperature-dependent Sellmeier coefficients and coherence length for cadmium telluride*

A temperature-dependent Sellmeier equation is calculated for CdTe. Using the derived Sellmeier equation, the coherence length for second harmonic generation was calculated as well as the variation of the coherence length with temperature. The predicted coherence length is found to be in good agreement with measured values.

Argon arc lamps

The spectra of several Ar arc lamps were measured in the 0.4–0.9-μm range. The voltage and current characteristics of these lamps filled with various Ar pressures were also measured. One of the lamps was then used to pump a Nd-YAG laser, and the same laser was also pumped with a common Xe arc lamp. A comparison of the laser performance with both arc lamps is presented.

Cr:YSAG — A Tunable Near-Infrared Laser Material

Cr:YSAG has been evaluated as a tunable laser material in the near-infrared region of the spectrum. Basic parameters such as the upper laser level lifetime and the fluorescent spectra have been measured. Gain, as a function of flashlamp energy and wavelength, has also been measured.as well as the flashlamp-induced loss at 0.532 and 1.064 µm.

Liquid nitrogen cooled laser rod holder design

A reliable Ho:YLF laser system has been successfully developed. Problems encountered in laser‐rod and support‐system design were unique and most difficult to solve. These problems include holding a fragile laser rod having nonisotropic thermal expantion with vacuum tight seals which can be thermally cycled. Experimentally proven solutions are described which should help others in developing new solid‐state laser systems.

Distributed aperture effect in laser rods with negative lenses

Negative lenses have been ground on the ends of laser rods to increase the TEM(00) mode volume. With the negative lenses on the ends, the laser rod acts like a distributed aperture. The distributed aperture radius and its effect on the useful volume of the laser rod are calculated. The mode radius and the diffraction loss for a laser rod with negative lenses ground on the ends are presented as a function of laser rod focal length and the Fresnel number.

Eye-Safe Solid-State Lasers For LIDAR Applications

Several solid-state lasers that operate in the eye-safe region of the spectrum could be employed in LIDAR applications. Although laser radar systems based on CO2 laser technology have successfully been employed in wind velocity LIDAR systems, several advantages would accrue if a shorter wavelength laser could be employed. Characteristics that normally improve as the wavelength decreases include: range resolution, velocity error, scattered signal strength, detector detectivity, and optics size. Disadvantage of operation at shorter wavelengths result primarily from the higher quantum-limited noise and increased susceptibility to atmospheric turbulence. However, if the wavelength becomes too short, eye safety problems may result, especially if coherent detection is required. Fortunately several solid-state lasers operate in the nominal eye-safe region, wavelengths longer than 1.5 μm. Solid-state lasers have the additional advantages of compact size and reliability. With the advent of diode pumping, these devices would also have the benefit of extremely long lifetime.