Spokesman Ralf Herrenbrueck said: "He concerned himself on one hand with medical treatment methods, on the other hand with types and ways of going about a suicide.
"In addition, on at least one day he concerned himself with search terms about cockpit doors and their security precautions.''
Based on that evidence, investigators said they believed Lubitz intentionally crashed Flight 9525, which was travelling from Barcelona to Duesseldorf, taking control of the aircraft while the pilot was locked out of the cockpit.
The second "black box" recovered is the flight data recorder (FDR) which should hold technical information on the time of radio transmissions and the plane's acceleration, airspeed, altitude and direction, plus the use of auto-pilot.
The "completely blackened" equipment was found near a ravine and was not discovered immediately because it was the same colour as the rocks, he said.
He said: "The second black box is an indispensable addition to understand what happened especially in the final moment of the flight."
He told the media 150 separate DNA profiles had been isolated from the crash site but he stressed that did not mean all the victims had been identified.
As each DNA set is matched to a victim, families will be notified immediately, he said,
He added 40 mobile phones had been recovered. He said they would be analysed in a laboratory but were "heavily damaged".
'Severe depression'
Also on Thursday, Germanwings said it was unaware that Lubitz had experienced depression while he was training to be a pilot.
Lufthansa confirmed on Tuesday that it knew six years ago that the co-pilot had suffered from an episode of "severe depression'' before he finished his flight training.
«We didn't know this,'' said Vanessa Torres, a spokeswoman for Lufthansa subsidiary Germanwings, which hired Lubitz in September 2013.
She could not explain why Germanwings had not been informed.
The final minutes
Lubitz began the jet's descent at 10:31 (09:31 GMT) on 24 March, shortly after the A320 had made its final contact with air traffic control.
Little more than eight minutes later, it had crashed into a mountain near Seyne-les-Alpes.