Ryan J. Mitchell, 36, of Frankford, was arrested on Thursday night.
Investigators say Mitchell repeatedly called, emailed and sent letters to a 38-year-old Sussex County woman.
The emails, dated February 27th through April 5th, were sent to the woman's workplace, police said.
The messages allegedly made unwelcome comments about the woman's appearance and Mitchell's feelings for her.
As the investigation continued, police say Mitchell was placed on suspension and advised not to contact the victim. However, police said, Mitchell continued emailing the woman.
Mitchell has been charged with one count of felony stalking.
He was arraigned and released on $500 unsecured bond.
Mitchell is a 15 year veteran of the state police and is assigned to Troop 4 in Georgetown. He is the Sergeant/supervisor of the Major Crimes Division and was responsible for overseeing detectives investigating Robberies, Serious Assaults and additional crimes against persons.