Lumentum shares surged 18.6% Monday following the company’s addition to the Nasdaq-100 Index.

Nasdaq announced Friday that Lumentum will join the index, replacing CoStar prior to market open on Monday, May 18, 2026. The Nasdaq-100 Index tracks the 100 largest non-financial companies listed on the Nasdaq stock exchange.

Index inclusion typically drives increased demand for a stock as index-tracking funds must purchase shares to match their benchmark portfolios. Passive funds that replicate the Nasdaq-100 will need to add Lumentum to their holdings.

Lumentum is a provider of optical and photonic products for communications and commercial laser applications. The company’s addition to the index marks a milestone in its market capitalization growth, as the Nasdaq-100 represents some of the largest companies trading on the exchange.