Is Kuhlau a classical era composer?

Yes, Frederik Kuhlau is considered a classical era composer. He was born in 1786, which places him squarely within the classical era, which is generally considered to have lasted from the mid-18th century to the early 19th century. Kuhlau's music exhibits many characteristics of the classical era, such as its clear and balanced textures, its use of sonata-allegro form, and its emphasis on melody and emotional expression.