Which Hindi author wrote the Urdu poet pen name rasa?

There is no known Hindi author who used the Urdu poet pen name "Rasa". The name "Rasa" (रस) itself is a significant term in Sanskrit and Hindi poetics, referring to aesthetic flavour or sentiment, but it's not typically used as a pen name in the way you're describing. It's possible you're misremembering the name or there's a confusion with another pen name or author.