Photon Bombs were powerful explosive weapons developed after the arrival of the Taelons on Earth. Portable hand held versions of these devices were capable of being made and needed to be carried on a persons back. Activation required a simple twist of the top part of the cylindrical device which generated a powerful explosion capable of overwhelming small shields.
One such bomb was used by a suicide squad that attacked on the Day of Sanctuary where an attempt was made against Resistance fighters who were seeking amnesty. (Episode: Take No Prisoners)