Memory chips have emerged as the hottest investing theme on Wall Street in 2026, but there might be another new frontier in the AI trade posed to fuel strong stock gains. AI bullishness has returned to markets, setting off a record-setting rally in stocks in the second quarter—and there's a common thread among some of the top gainers beyond memory plays. Optics stocks have become some of the strongest gainers as investors assess the next bottleneck in the AI trade. Optical technology