(Reuters) - Lumentum Holdings Inc on Thursday reiterated its deal with laser maker Coherent Inc as superior to the $6 billion takeover offer from MKS Instruments, which it believed would face substantial regulatory hurdles. Lumentum said the proposed deal of MKS and Coherent has significant product and revenue overlaps, which would likely result in extended negotiation with antitrust regulators. Last month, the optical fiber specialist agreed to a $5.7 billion deal with Coherent, where the company’s stockholders were to receive $100 per share in cash and 1.1851 shares of Lumentum common stock for each share held. The cash-and-stock offer by MKS valued Coherent shares at $240 apiece.