Marine-based deoxyribonucleic acid (DNA), purified from waste products of the Japanese fishing industry, has recently become a new material of interest in photonics applications. The water soluble DNA is precipitated with a surfactant complex, hexadecyltrimethyl-ammonium chloride (CTMA), to form a water insoluble complex, DNA-CTMA, for application as a nonlinear optical material. In order to fabricate an all-DNA-based waveguide, it was necessary to crosslink the DNA-CTMA films. Crosslinking makes the films resistant to their initial solvent; this permits spin-coating of successive DNA-CTMA layers without solvent damage. A chromophore dye is added to the core layer to allow for an electro-optic coefficient to be induced through contact poling. Through contact poling, an electro-optic (EO) coefficient comparable to that in other polymers was demonstrated in crosslinked DNA-CTMA films with the chromophore dye Disperse Red 1. This EO effect allowed for the creation of the first all-DNA-based EO waveguide modulator. The performance of the modulator is described.