** Optical devices maker Coherent shares COHR.N plunge 22.6% to $88.61, heading for their largest single-day decline since August 2023
** Co forecasts Q1 revenue between $1.46 bln and $1.60 bln, with the midpoint falling short of analysts' $1.54 bln estimate, as per LSEG data
** However, COHR beats Wall Street estimates for Q4 adj. profit and revenue
** Analyst reactions are mixed, with at least two brokerages cutting PT on the stock, while four others raising
** Brokerage firm BofA also downgrades the stock to "neutral" from "buy", noting that COHR is showing signs of deceleration relative to both its own past performance and industry peers in a high-growth AI market
** In contrast, Citi Research calls concerns about lost AI transceiver market share "premature" given COHR's 49% networking growth over the past year
** Including session's moves, stock is down 6.6% YTD, compared with a 17.3% increase in the Philadelphia SE semiconductor index .SOX