Patent ID: 7075723

Claim:
An apparatus comprising: a virtually imaged phased array (VIPA) generator receiving an input light at a respective wavelength and producing a corresponding collimated output light traveling from the VIPA generator in a direction determined by the wavelength of the input light; a reflecting surface reflecting the output light back to the VIPA generator; and at least one phase mask causing the input light received by the VIPA generator to have a double-hump shaped far field distribution, the reflecting surface having different curvatures at different positions along a direction perpendicular to a plane which includes the traveling directions of collimated output light from the VIPA generator for input light at different wavelengths, curvature c(y) of the reflecting surface being as follows: c â¡ ( y ) = K 8 â¢ f 4 â¢ y 4 + K â¢ â¢ Î˜ 2 â¢ f 3 â¢ y 3 + K â¢ â¢ Î˜ 2 - ( f - a ) 2 â¢ f 2 â¢ y 2 where y=is a light focusing position on the reflecting surface, Î¸=is an input angle of the input light to the VIPA generator in air, f=is a focal length of a lens or mirror focusing the output light traveling from the VIPA generator onto the reflecting surface, a=is a depth of a center beam waist of the VIPA generator, and K is a constant so that chromatic dispersion equals âˆ’2n 4 K/cÎ», with c being the speed of light, Î» being wavelength, and n being a refractive index of material forming the VIPA generator.