Lumentum increased its offer to buy Coherent to $6.9 billion, or $275 per share. Coherent shareholders could receive $220 and 0.61 shares of Lumentum common stock for each of their securities. Earlier, Coherent's board of directors considered the latest II-VI merger offer to be the best option, based on the company's valuation of $6.8 billion, or $272.68 per share.