O CAPTAIN MY CAPTAIN-AS A POEM OF JUXTAPOSE OF GRIEF & EXHALTATIONTHE POEM IS WRITTEN BY WALT WHITMAN
I'm not to sure if you are looking for this idea to be explained or if you are asking if it is true. With that being said, I'll try to answer both.
Yes, "O Captain, My Captain" is a poem that juxtaposes grief and exaltation. Walt Whitman was a very big admirer of Abraham Lincoln, and his death really struck Whitman.
This poem is able to put feelings of sorrow and mourning along side the excitement of memorializing and exalting through Whitman's use of symbolism. The ship, and subsequently the captain, stand it for the nation and Lincoln. This ship has been off to battle and is returning as victorious, however the casualties were prominent, the captain lay slain. Whitman uses this to show how amazing and accomplished Lincoln had made the nation, re-uniting the divided North and South, ending slavery, and turning this nation down a straight path. However, while the nation is beginning to get back on track to greatness, Lincoln is assassinated. Whitman is upset and mourning, but knows the greater good Lincoln caused.