who was Kalidas? how did he enrichsanskrit literature?

Kalidasa was the court poet of the Gupta King Vikramaditya. There are many legends surrounding Kaidasa, and very liitle accurate history. This you find usually in ancient India due the authors and poets not bothering to record anything about themselves or the era in which they lived. Thus Kalidasa's period is variously stated as any where between 2nd Century AD to 5th Century AD. Kalidasa was a poet and a Dramatist. One of his best poetical work is Raghuvamsha. Of the many dramas he had written Abhjnana Shankuntalam is perhaps the best. There about 8-10 of his famous works.

His style of writing is called the vaidarbhi style where the words chosen are smooth and the poetry is lyrical. He is known for his similes. His style had been copied by many who came after him. Many later poets would compare themselves to him and declare that they were not inferior if not better. His works are studied at the second level of the famous pancha-kavya group.