A multipass cell, includes a body; a cavity formed within the body; a first spherical or toroidal mirror at a first end of the cavity; and a second spherical, toroidal or cylindrical mirror at the opposite end of the cavity. The first mirror and the second mirror are configured to reflect a beam entering the cavity next to an outer edge of the first or the second mirror a predetermined number of times so that the beam propagates substantially in a single plane between the first and the second mirror. Also an optical detection system includes the multipass cell; an optical source configured to direct a beam into the cavity; and a detector element configured to receive the beam exiting the cavity or configured to receive the acoustic signal generated by light absorption in the cavity.