“Police officer” or “officer”: Any person who (1) is appointed to the police force of a police department and sworn and commissioned to perform police duties; and (2) within 3 months after receiving his or her first appointment and, if reappointed, within 3 months thereafter, or as otherwise provided in Section 3-109, makes written application to the board to come under the provisions of this Article.
     Police officers serving initial probationary periods, if otherwise eligible, shall be police officers within the meaning of this Section.