Mr Devadas, a Padma Shri awardee, died of cardiac arrest at Hebrew Home of Greater Washington on Friday. He is survived by his wife and eight children. He was 93.
In a career spanning more than five decades, Mr Devadas has covered US visit of every Indian Prime Minister from Jawaharlal Nehru to Manmohan Singh besides photographing every US president from John F Kennedy to George W Bush. He could not cover Narendra Modi's visit in September.
"He was a chronicler par excellence of India-US relations and he had a memory of key events in this chequered relationship that stretched back to the Kennedy Administration when our then Ambassador B K Nehru encouraged him to take up media-related works for the Embassy," former Indian Ambassador to the US Nirupama Rao, said.
Mr Devadas had celebrated his 93rd birthday in the suburb of Washington earlier this summer which was attended by some of his close friends and community leaders.
In 2002, he was bestowed with the Padma Shri award, India's one of the highest civilian awards. As he could not travel to New Delhi to receive the award on health grounds, then Indian diplomat Lalit Mansingh presented it to him at a convention of the Federation of Kerala Association in Chicago.
After having worked as an administrative assistant at the BHU, Mr Devadas came to the US in 1955 to attend a one year program at the Pendle Hill Quaker Center for Study and Contemplation.
Then he moved to New York to attend New School for Social Research, where he took two courses in journalism and public relations that sparked his interest in photography.
For several decades, Mr Devadas worked as an official photographer of the Indian Embassy in Washington.
"He had met, listened to and spoken with Gandhiji and many others who belonged to India's greatest generation. He knew Madan Mohan Malviya and I spoke with him at length about Malviya when I was to speak to a group of BHU alumni at our Embassy in DC (Washington) in 2013," Mr Rao said.