A horizontal cavity, surface emitting laser with internal polarization rotation is used in thermally assisted recording in hard disk drives. The sponge-like chitosan structure is compressed by application of heat and pressure to reduce the thickness and increase the density of the sponge-like chitosan structure to form a densified chitosan structure. A plurality of different designs and configurations of cap can thereby be lodged and rotationally fixed within the socket to remove the cap from and replace the cap, for example on a battery cell. still drying the wet spherical particles and removing volatile liquid to form flowable pre-agglomerated particles with increased bulk density; d). The first doping region has a second conductivity and the second doping region has the first conductivity type.