In this article, a novel design of a millimeter‐wave antenna array consisting of linearly tapered slotline antenna elements is presented. The antenna array was designed for the frequency range from 50 to 600 GHz. A numerical model of the antenna array was developed in CST microwave studio. To optimize the antenna model, a novel real‐coded genetic algorithm was proposed. The optimized antenna was fabricated from a low‐loss dielectric substrate ARLON CuClad 217, and its parameters were experimentally verified. The antenna was designed for quasi‐optical terahertz spectroscopy applications. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1043–1046, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25110