Philip Gleckman

Achievement of ultrahigh solar concentration with potential for efficient laser pumping

Measurements are reported of the irradiance produced by a two-stage solar concentrator designed to approach the thermodynamic limit. Sunlight is collected by a 40.6-cm diam parabolic primary which forms a 0.98-cm diam image. The image is reconcentrated by a nonimaging refracting secondary with index n = 1.53 to a final aperture 1.27 mm in diameter. Thus the geometrical concentration ratio is 102, 000. The highest irradiance value achieved was 4.4 +/- 0.2 kW cm(-2), or 56,000 +/- 5000 suns, relative to a solar disk insolation of 800 W m(-2). This is greater than the previous peak solar irradiance record by nearly a factor of 3, and it is 68% of that existing at the solar surface itself. The efficiency with which we concentrated 55 W of sunlight to a small spot suggests that our two-stage system would be an excellent candidate for solar pumping of solid state lasers.

Approaching the irradiance of the sun through nonimaging optics

Through the use of nonimaging techniques, a solar concentrator is designed that increases the solar flux density achievable. (AIP)

Nonimaging concentrators for diode-pumped slab lasers

Diode-pumped slab lasers require concentrators for high-average power operation. We detail the properties of diode lasers and slab lasers which set the concentration requirements and the concentrator design methodologies that are used, and describe some concentrator designs used in high-average power slab lasers at Lincoln Laboratory.

Very high temperature fiber processing and testing through the use of ultrahigh solar energy concentration

We have demonstrated the feasibility of a high temperature cool-wall optical furnace that harnesses the unique power of concentrated solar heating for advanced materials processing and testing. Out small-scale test furnace achieved temperatures as high as 2400 C within a 10 mm X 0.44 mm cylindrical hot-zone. Optimum performance and efficiency resulted from an innovative two-stage optical design using a long-focal length, point-focus, conventional primary concentrator and a non-imaging secondary concentrator specifically designed for the cylindrical geometry of the target fiber. A scale-up analysis suggests that even higher temperatures can be achieved over hot zones large enough for practical commercial fiber post- processing and testing.

Phase space calculation of bend loss in rectangular light pipes

Angular momentum conservation and phase space are used for an exact calculation of bend loss in rectangular light pipes without rayiracing. It is found that the loss fraction ofrays in the bend plane is greater than that of the full 3-D distribution for any bend radius. There is excellent agreement between the calculated and measured loss.

ATTAINING THE MAXIMUM SOLAR CONCENTRATION

ABSTRACT We discuss methods of producing and measuring solar irradiance as high as 70,00 suns, six times higher than the irradiance achieved by the best paraboloidal furnace. With such an irradiance it may be possible to pump a dye laser.