The company said the board considered the comparative benefits and risks of both bids, including long-term and near-term financial opportunities and risks associated with each bid.
Lumentum said that Coherent's board chose to accept an offer "that is inferior in overall value and cash consideration."
The winning terms call for II-VI to pay $222 cash and 0.91 share for each Coherent share.
Coherent will also pay Lumentum a breakup fee of $217.6 million as part of their previous agreement.
Lumentum's most recent offer was valued at $283.12 a share compared with II-VI's at about $281.21, based on closing prices Wednesday.
Earlier this week, Lumentum had raised its bid to $230 a share cash and 0.6724 share for each Coherent share.
Coherent's sale saga dates to mid-January when Lumentum initially proposed a bid valued at about $5.7 billion.
Lumentum was then outbid by unsolicited offers from MKS Instruments and then II-VI in February.
Coherent's shares at last check were down 1% at $255. Lumentum's jumped 5.2% to $83.11. And II-VI shares were down 6.4% at $62.95.