As the response above suggests, there are many distinguished writers belonging to the Indian diaspora. In order to write an essay on the topic, you need to narrow your subject matter. There are several ways you could narrow your focus:
Chronological: you could write an essay about the origins of Indian diaspora literature or a specific period within it.
Linguistic: Although much diaspora literature is in English, you could look at the decisions of diaspora writers to write in the languages of the countries to which they migrated or whether to use Indian dialects.
Ethnic/caste: You could choose a focus on a regional tradition, such as the Punjabi diaspora, or a caste one -- a great deal has been published about dalit literature.
Region: How does the Indian diaspora literature from Africa compare with that in Canada? The US? Britain? Could you focus on one area or region?
Religion: Another way to narrow focus is to choose a religious tradition -- e.g. the Indian Islamic diaspora.
Overall, for a coherent essay, you might want to find one theme that seems to predominate in one particular type of Indian diaspora literature and make that your focus.
The Indian diaspora today constitutes an important, and in some respects unique, force in world culture. The origins of the modern Indian diaspora lie mainly in the subjugation of India by the British and its incorporation into the British empire. Indians were taken over as indentured labor to far-flung parts of the empire in the nineteenth-century, a circumstance to which the modern Indian populations of Fiji, Mauritius, Guyana, Trinidad, Surinam, Malaysia, South Africa, Sri Lanka, and other places attest in their own peculiar ways. Over two million Indian men fought on behalf of the empire in numerous wars, including the Boer War and the two World Wars, and some remained behind to claim the land on which they had fought as their own. As if in emulation of their ancestors, many Gujarati traders once again left for East Africa in large numbers in the early part of the twentieth century. Finally, in the post-World War II period, the dispersal of Indian labor and professionals has been a nearly world-wide phenomenon. Indians, and other South Asians, provided the labor that helped in the reconstruction of war-torn Europe, particularly the United Kingdom and the Netherlands, and in more recent years unskilled labor from South Asia has been the main force in the transformation of the physical landscape of much of the Middle East. Meanwhile, in countries such as the United States, Canada, and Australia, Indians have made their presence visibly felt in the professions.
The Literature of the Indian Diaspora constitutes a major study of the literature and other cultural texts of the Indian diaspora. It is also an important contribution to diaspora theory in general. Examining both the 'old' Indian diaspora of early capitalism, following the abolition of slavery, and the 'new' diaspora linked to movements of late capital, Mishra argues that a full understanding of the Indian diaspora can only be achieved if attention is paid to the particular locations of both the 'old' and the 'new' in nation states. Applying a theoretical framework based on trauma, mourning/impossible mourning, spectres, identity, travel, translation, and recognition, Mishra uses the term 'imaginary' to refer to any ethnic enclave in a nation-state that defines itself, consciously or unconsciously, as a group in displacement. He examines the works of key writers, many now based across the globe in Canada, Australia, America and the UK, -- V.S. Naipaul, Salman Rushdie, M.G. Vassanji, Shani Mootoo, Bharati Mukherjee, David Dabydeen, Rohinton Mistry and Hanif Kureishi, among them -- to show how they exemplify both the diasporic imaginary and the respective traumas of the 'old' and 'new' Indian diasporas.